This has been broken forever, and nobody ever really noticed because
it's purely a performance issue.

Long long ago, in commit 6175ddf0 ("x86: Clean up mem*io functions")
Brian Gerst simplified the memory copies to and from iomem, since on
x86, the instructions to access iomem are exactly the same as the
regular instructions.

That is technically true, and things worked, and nobody said anything.
Besides, back then the regular memcpy was pretty simple and worked fine.

Nobody noticed except for David Laight, that is.  David has a testing a
TLP monitor he was writing for an FPGA, and has been occasionally
complaining about how memcpy_toio() writes things one byte at a time.

Which is completely unacceptable from a performance standpoint, even if
it happens to technically work.

The reason it's writing one byte at a time is because while it's
technically true that accesses to iomem are the same as accesses to
regular memory on x86, the _granularity_ (and ordering) of accesses
matter to iomem in ways that they don't matter to regular cached memory.

In particular, when ERMS is set, we default to using "rep movsb" for
larger memory copies.  That is indeed perfectly fine for real memory,
since the whole point is that the CPU is going to do cacheline
optimizations and executes the memory copy efficiently for cached
memory.

With iomem? Not so much.  With iomem, "rep movsb" will indeed work, but
it will copy things one byte at a time. Slowly and ponderously.

Now, originally, back in 2010 when commit 6175ddf0

 was done, we
didn't use ERMS, and this was much less noticeable.

Our normal memcpy() was simpler in other ways too.

Because in fact, it's not just about using the string instructions.  Our
memcpy() these days does things like "read and write overlapping values"
to handle the last bytes of the copy.  Again, for normal memory,
overlapping accesses isn't an issue.  For iomem? It can be.

So this re-introduces the specialized memcpy_toio(), memcpy_fromio() and
memset_io() functions.  It doesn't particularly optimize them, but it
tries to at least not be horrid, or do overlapping accesses.  In fact,
this uses the existing __inline_memcpy() function that we still had
lying around that uses our very traditional "rep movsl" loop followed by
movsw/movsb for the final bytes.

Somebody may decide to try to improve on it, but if we've gone almost a
decade with only one person really ever noticing and complaining, maybe
it's not worth worrying about further, once it's not _completely_ broken?

Reported-by: David Laight <David.Laight@aculab.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This actually enables the __put_user_goto() functionality in
unsafe_put_user().

For an example of the effect of this, this is the code generated for the

        unsafe_put_user(signo, &infop->si_signo, Efault);

in the waitid() system call:

	movl %ecx,(%rbx)        # signo, MEM[(struct __large_struct *)_2]

It's just one single store instruction, along with generating an
exception table entry pointing to the Efault label case in case that
instruction faults.

Before, we would generate this:

	xorl    %edx, %edx
	movl %ecx,(%rbx)        # signo, MEM[(struct __large_struct *)_3]
        testl   %edx, %edx
        jne     .L309

with the exception table generated for that 'mov' instruction causing us
to jump to a stub that set %edx to -EFAULT and then jumped back to the
'testl' instruction.

So not only do we now get rid of the extra code in the normal sequence,
we also avoid unnecessarily keeping that extra error register live
across it all.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is finally the actual reason for the odd error handling in the
"unsafe_get/put_user()" functions, introduced over three years ago.

Using a "jump to error label" interface is somewhat odd, but very
convenient as a programming interface, and more importantly, it fits
very well with simply making the target be the exception handler address
directly from the inline asm.

The reason it took over three years to actually do this? We need "asm
goto" support for it, which only became the default on x86 last year.
It's now been a year that we've forced asm goto support (see commit
e501ce95

 "x86: Force asm-goto"), and so let's just do it here too.

[ Side note: this commit was originally done back in 2016. The above
  commentary about timing is obviously about it only now getting merged
  into my real upstream tree     - Linus ]

Sadly, gcc still only supports "asm goto" with asms that do not have any
outputs, so we are limited to only the put_user case for this.  Maybe in
several more years we can do the get_user case too.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Originally, the rule used to be that you'd have to do access_ok()
separately, and then user_access_begin() before actually doing the
direct (optimized) user access.

But experience has shown that people then decide not to do access_ok()
at all, and instead rely on it being implied by other operations or
similar.  Which makes it very hard to verify that the access has
actually been range-checked.

If you use the unsafe direct user accesses, hardware features (either
SMAP - Supervisor Mode Access Protection - on x86, or PAN - Privileged
Access Never - on ARM) do force you to use user_access_begin().  But
nothing really forces the range check.

By putting the range check into user_access_begin(), we actually force
people to do the right thing (tm), and the range check vill be visible
near the actual accesses.  We have way too long a history of people
trying to avoid them.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When commit fddcd00a ("drm/i915: Force the slow path after a
user-write error") unified the error handling for various user access
problems, it didn't do the user_access_end() that is needed for the
unsafe_put_user() case.

It's not a huge deal: a missed user_access_end() will only mean that
SMAP protection isn't active afterwards, and for the error case we'll be
returning to user mode soon enough anyway.  But it's wrong, and adding
the proper user_access_end() is trivial enough (and doing it for the
other error cases where it isn't needed doesn't hurt).

I noticed it while doing the same prep-work for changing
user_access_begin() that precipitated the access_ok() changes in commit
96d4f267 ("Remove 'type' argument from access_ok() function").

Fixes: fddcd00a

 ("drm/i915: Force the slow path after a user-write error")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: stable@kernel.org # v4.20
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

These two architectures actually had an intentional use of the 'type'
argument to access_ok() just to avoid warnings.

I had actually noticed the powerpc one, but forgot to then fix it up.
And I missed the sparc32 case entirely.

This is hopefully all of it.

Reported-by: Mathieu Malaterre <malat@debian.org>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 96d4f267

 ("Remove 'type' argument from access_ok() function")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument
of the user address range verification function since we got rid of the
old racy i386-only code to walk page tables by hand.

It existed because the original 80386 would not honor the write protect
bit when in kernel mode, so you had to do COW by hand before doing any
user access.  But we haven't supported that in a long time, and these
days the 'type' argument is a purely historical artifact.

A discussion about extending 'user_access_begin()' to do the range
checking resulted this patch, because there is no way we're going to
move the old VERIFY_xyz interface to that model.  And it's best done at
the end of the merge window when I've done most of my merges, so let's
just get this done once and for all.

This patch was mostly done with a sed-script, with manual fix-ups for
the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form.

There were a couple of notable cases:

 - csk...

Pull file locking bugfix from Jeff Layton:
 "This is a one-line fix for a bug that syzbot turned up in the new
  patches to mitigate the thundering herd when a lock is released"

* tag 'locks-v4.21-2' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  locks: fix error in locks_move_blocks()

Pull sound fixes from Takashi Iwai:
 "Among a few HD-audio fixes, the only significant one is the regression
  fix on some machines like Dell XPS due to the default binding changes.
  We ended up reverting the whole since the fix for ASoC HD-audio driver
  won't be available immediately"

* tag 'sound-fix-4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: hda - Revert DSP detection on legacy HD-audio driver
  ALSA: hda/tegra: clear pending irq handlers
  ALSA: hda/realtek: Enable the headset mic auto detection for ASUS laptops

Pull networking fixes from David Miller:
 "Several fixes here. Basically split down the line between newly
  introduced regressions and long existing problems:

   1) Double free in tipc_enable_bearer(), from Cong Wang.

   2) Many fixes to nf_conncount, from Florian Westphal.

   3) op->get_regs_len() can throw an error, check it, from Yunsheng
      Lin.

   4) Need to use GFP_ATOMIC in *_add_hash_mac_address() of fsl/fman
      driver, from Scott Wood.

   5) Inifnite loop in fib_empty_table(), from Yue Haibing.

   6) Use after free in ax25_fillin_cb(), from Cong Wang.

   7) Fix socket locking in nr_find_socket(), also from Cong Wang.

   8) Fix WoL wakeup enable in r8169, from Heiner Kallweit.

   9) On 32-bit sock->sk_stamp is not thread-safe, from Deepa Dinamani.

  10) Fix ptr_ring wrap during queue swap, from Cong Wang.

  11) Missing shutdown callback in hinic driver, from Xue Chaojing.

  12) Need to return NULL on error from ip6_neigh_lookup(), from Stefano
      Brivio.

  13) BPF out of bounds speculation fixes from Daniel Borkmann"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (57 commits)
  ipv6: Consider sk_bound_dev_if when binding a socket to an address
  ipv6: Fix dump of specific table with strict checking
  bpf: add various test cases to selftests
  bpf: prevent out of bounds speculation on pointer arithmetic
  bpf: fix check_map_access smin_value test when pointer contains offset
  bpf: restrict unknown scalars of mixed signed bounds for unprivileged
  bpf: restrict stack pointer arithmetic for unprivileged
  bpf: restrict map value pointer arithmetic for unprivileged
  bpf: enable access to ax register also from verifier rewrite
  bpf: move tmp variable into ax register in interpreter
  bpf: move {prev_,}insn_idx into verifier env
  isdn: fix kernel-infoleak in capi_unlocked_ioctl
  ipv6: route: Fix return value of ip6_neigh_lookup() on neigh_create() error
  net/hamradio/6pack: use mod_timer() to rearm timers
  net-next/hinic:add shutdown callback
  net: hns3: call hns3_nic_net_open() while doing HNAE3_UP_CLIENT
  ip: validate header length on virtual device xmit
  tap: call skb_probe_transport_header after setting skb->dev
  ptr_ring: wrap back ->producer in __ptr_ring_swap_queue()
  net: rds: remove unnecessary NULL check
  ...

IPv6 does not consider if the socket is bound to a device when binding
to an address. The result is that a socket can be bound to eth0 and then
bound to the address of eth1. If the device is a VRF, the result is that
a socket can only be bound to an address in the default VRF.

Resolve by considering the device if sk_bound_dev_if is set.

This problem exists from the beginning of git history.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Dump of a specific table with strict checking enabled is looping. The
problem is that the end of the table dump is not marked in the cb. When
dumping a specific table, cb args 0 and 1 are not used (they are the hash
index and entry with an hash table index when dumping all tables). Re-use
args[0] to hold a 'done' flag for the specific table dump.

Fixes: 13e38901

 ("net/ipv6: Plumb support for filtering route dumps")
Reported-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Pull input updates from Dmitry Torokhov:
 "A tiny pull request this merge window unfortunately, should get more
  material in for the next release:

   - new driver for Raspberry Pi's touchscreen (firmware interface)

   - miscellaneous input driver fixes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: elan_i2c - add ACPI ID for touchpad in ASUS Aspire F5-573G
  Input: atmel_mxt_ts - don't try to free unallocated kernel memory
  Input: drv2667 - fix indentation issues
  Input: touchscreen - fix coding style issue
  Input: add official Raspberry Pi's touchscreen driver
  Input: nomadik-ske-keypad - fix a loop timeout test
  Input: rotary-encoder - don't log EPROBE_DEFER to kernel log
  Input: olpc_apsp - remove set but not used variable 'np'
  Input: olpc_apsp - enable the SP clock
  Input: olpc_apsp - check FIFO status on open(), not probe()
  Input: olpc_apsp - drop CONFIG_OLPC dependency
  clk: mmp2: add SP clock
  dt-bindings: marvell,mmp2: Add clock id for the SP clock
  Input: ad7879 - drop platform data support

Pull virtio/vhost updates from Michael Tsirkin:
"Features, fixes, cleanups:

   - discard in virtio blk

   - misc fixes and cleanups"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  vhost: correct the related warning message
  vhost: split structs into a separate header file
  virtio: remove deprecated VIRTIO_PCI_CONFIG()
  vhost/vsock: switch to a mutex for vhost_vsock_hash
  virtio_blk: add discard and write zeroes support

Pull more block updates from Jens Axboe:

 - Dead code removal for loop/sunvdc (Chengguang)

 - Mark BIDI support for bsg as deprecated, logging a single dmesg
   warning if anyone is actually using it (Christoph)

 - blkcg cleanup, killing a dead function and making the tryget_closest
   variant easier to read (Dennis)

 - Floppy fixes, one fixing a regression in swim3 (Finn)

 - lightnvm use-after-free fix (Gustavo)

 - gdrom leak fix (Wenwen)

 - a set of drbd updates (Lars, Luc, Nathan, Roland)

* tag 'for-4.21/block-20190102' of git://git.kernel.dk/linux-block: (28 commits)
  block/swim3: Fix regression on PowerBook G3
  block/swim3: Fix -EBUSY error when re-opening device after unmount
  block/swim3: Remove dead return statement
  block/amiflop: Don't log error message on invalid ioctl
  gdrom: fix a memory leak bug
  lightnvm: pblk: fix use-after-free bug
  block: sunvdc: remove redundant code
  block: loop: remove redundant cod...

Pull libata fix from Jens Axboe:
 "This libata change missed the original libata pull request.

  Just a single fix in here, fixing a missed reference drop"

* tag 'for-4.21/libata-20190102' of git://git.kernel.dk/linux-block:
  ata: pata_macio: add of_node_put()

Pull more clk updates from Stephen Boyd:
 "One more patch to generalize a set of DT binding defines now before
  -rc1 comes out.

  This way the SoC DTS files can use the proper defines from a stable
  tag"

* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
  clk: imx8qxp: make the name of clock ID generic

Pull device properties framework fixes from Rafael Wysocki:
 "Fix two potential NULL pointer dereferences found by Coverity in the
  software nodes code introduced recently (Colin Ian King)"

* tag 'devprop-4.21-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  drivers: base: swnode: check if swnode is NULL before dereferencing it
  drivers: base: swnode: check if pointer p is NULL before dereferencing it

Pull mailbox updates from Jassi Brar:

 - Introduce device-managed registration
   devm_mbox_controller_un/register and convert drivers to use it

 - Introduce flush api to support clients that must busy-wait in atomic
   context

 - Support multiple controllers per device

 - Hi3660: a bugfix and constify ops structure

 - TI-MsgMgr: off by one bugfix.

 - BCM: switch to spdx license

 - Tegra-HSP: support for shared mailboxes and suspend/resume.

* tag 'mailbox-v4.21' of git://git.linaro.org/landing-teams/working/fujitsu/integration: (30 commits)
  mailbox: tegra-hsp: Use device-managed registration API
  mailbox: tegra-hsp: use devm_kstrdup_const()
  mailbox: tegra-hsp: Add suspend/resume support
  mailbox: tegra-hsp: Add support for shared mailboxes
  dt-bindings: tegra186-hsp: Add shared mailboxes
  mailbox: Allow multiple controllers per device
  mailbox: Support blocking transfers in atomic context
  mailbox: ti-msgmgr: Use device-managed registration API
  mailbox: stm32-ipcc: Use device-managed registration API
  mailbox: rockchip: Use device-managed registration API
  mailbox: qcom-apcs: Use device-managed registration API
  mailbox: platform-mhu: Use device-managed registration API
  mailbox: omap: Use device-managed registration API
  mailbox: mtk-cmdq: Remove needless devm_kfree() calls
  mailbox: mtk-cmdq: Use device-managed registration API
  mailbox: xgene-slimpro: Use device-managed registration API
  mailbox: sti: Use device-managed registration API
  mailbox: altera: Use device-managed registration API
  mailbox: imx: Use device-managed registration API
  mailbox: hi6220: Use device-managed registration API
  ...

Pull UML updates from Richard Weinberger:

 - DISCARD support for our block device driver

 - Many TLB flush optimizations

 - Various smaller fixes

 - And most important, Anton agreed to help me maintaining UML

* 'for-linus-4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
  um: Remove obsolete reenable_XX calls
  um: writev needs <sys/uio.h>
  Add Anton Ivanov to UML maintainers
  um: remove redundant generic-y
  um: Optimize Flush TLB for force/fork case
  um: Avoid marking pages with "changed protection"
  um: Skip TLB flushing where not needed
  um: Optimize TLB operations v2
  um: Remove unnecessary faulted check in uaccess.c
  um: Add support for DISCARD in the UBD Driver
  um: Remove unsafe printks from the io thread
  um: Clean-up command processing in UML UBD driver
  um: Switch to block-mq constants in the UML UBD driver
  um: Make GCOV depend on !KCOV
  um: Include sys/uio.h to have writev()
  um: Add HAVE_DEBUG_BUGVERBOSE
  um: Update maintainers file entry

Pull s390 updates from Martin Schwidefsky:

 - A larger update for the zcrypt / AP bus code:
    + Update two inline assemblies in the zcrypt driver to make gcc happy
    + Add a missing reply code for invalid special commands for zcrypt
    + Allow AP device reset to be triggered from user space
    + Split the AP scan function into smaller, more readable functions

 - Updates for vfio-ccw and vfio-ap
    + Add maintainers and reviewer for vfio-ccw
    + Include facility.h in vfio_ap_drv.c to avoid fragile include chain
    + Simplicy vfio-ccw state machine

 - Use the common code version of bust_spinlocks

 - Make use of the DEFINE_SHOW_ATTRIBUTE

 - Fix three incorrect file permissions in the DASD driver

 - Remove bit spin-lock from the PCI interrupt handler

 - Fix GFP_ATOMIC vs GFP_KERNEL in the PCI code

* tag 's390-4.21-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/zcrypt: rework ap scan bus code
  s390/zcrypt: make sysfs reset attribute trigger queue reset
  s390/pci: fix sleeping in atomic during hotplug
  s390/pci: remove bit_lock usage in interrupt handler
  s390/drivers: fix proc/debugfs file permissions
  s390: convert to DEFINE_SHOW_ATTRIBUTE
  MAINTAINERS/vfio-ccw: add Farhan and Eric, make Halil Reviewer
  vfio: ccw: Merge BUSY and BOXED states
  s390: use common bust_spinlocks()
  s390/zcrypt: improve special ap message cmd handling
  s390/ap: rework assembler functions to use unions for in/out register variables
  s390: vfio-ap: include <asm/facility> for test_facility()

After moving all requests from
   fl->fl_blocked_requests
to
   new->fl_blocked_requests

it is nonsensical to do anything to all the remaining elements, there
aren't any.  This should do something to all the requests that have been
moved. For simplicity, it does it to all requests in the target list.

Setting "f->fl_blocker = new" to all members of new->fl_blocked_requests
is "obviously correct" as it preserves the invariant of the linkage
among requests.

Reported-by:  <syzbot+239d99847eb49ecb3899@syzkaller.appspotmail.com>
Fixes: 5946c431

 ("fs/locks: allow a lock request to block other requests.")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

Alexei Starovoitov says:

====================
pull-request: bpf 2019-01-02

The following pull-request contains BPF updates for your *net* tree.

The main changes are:

1) prevent out of bounds speculation on pointer arithmetic, from Daniel.

2) typo fix, from Xiaozhou.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

Pull NFS client updates from Anna Schumaker:
 "Stable bugfixes:
   - xprtrdma: Yet another double DMA-unmap # v4.20

  Features:
   - Allow some /proc/sys/sunrpc entries without CONFIG_SUNRPC_DEBUG
   - Per-xprt rdma receive workqueues
   - Drop support for FMR memory registration
   - Make port= mount option optional for RDMA mounts

  Other bugfixes and cleanups:
   - Remove unused nfs4_xdev_fs_type declaration
   - Fix comments for behavior that has changed
   - Remove generic RPC credentials by switching to 'struct cred'
   - Fix crossing mountpoints with different auth flavors
   - Various xprtrdma fixes from testing and auditing the close code
   - Fixes for disconnect issues when using xprtrdma with krb5
   - Clean up and improve xprtrdma trace points
   - Fix NFS v4.2 async copy reboot recovery"

* tag 'nfs-for-4.21-1' of git://git.linux-nfs.org/projects/anna/linux-nfs: (63 commits)
  sunrpc: convert to DEFINE_SHOW_ATTRIBUTE
  sunrpc: Add xprt after nfs4_test_session_trunk()
  sunrpc: convert unnecessary GFP_ATOMIC to GFP_NOFS
  sunrpc: handle ENOMEM in rpcb_getport_async
  NFS: remove unnecessary test for IS_ERR(cred)
  xprtrdma: Prevent leak of rpcrdma_rep objects
  NFSv4.2 fix async copy reboot recovery
  xprtrdma: Don't leak freed MRs
  xprtrdma: Add documenting comment for rpcrdma_buffer_destroy
  xprtrdma: Replace outdated comment for rpcrdma_ep_post
  xprtrdma: Update comments in frwr_op_send
  SUNRPC: Fix some kernel doc complaints
  SUNRPC: Simplify defining common RPC trace events
  NFS: Fix NFSv4 symbolic trace point output
  xprtrdma: Trace mapping, alloc, and dereg failures
  xprtrdma: Add trace points for calls to transport switch methods
  xprtrdma: Relocate the xprtrdma_mr_map trace points
  xprtrdma: Clean up of xprtrdma chunk trace points
  xprtrdma: Remove unused fields from rpcrdma_ia
  xprtrdma: Cull dprintk() call sites
  ...

Pull nfsd updates from Bruce Fields:
 "Thanks to Vasily Averin for fixing a use-after-free in the
  containerized NFSv4.2 client, and cleaning up some convoluted
  backchannel server code in the process.

  Otherwise, miscellaneous smaller bugfixes and cleanup"

* tag 'nfsd-4.21' of git://linux-nfs.org/~bfields/linux: (25 commits)
  nfs: fixed broken compilation in nfs_callback_up_net()
  nfs: minor typo in nfs4_callback_up_net()
  sunrpc: fix debug message in svc_create_xprt()
  sunrpc: make visible processing error in bc_svc_process()
  sunrpc: remove unused xpo_prep_reply_hdr callback
  sunrpc: remove svc_rdma_bc_class
  sunrpc: remove svc_tcp_bc_class
  sunrpc: remove unused bc_up operation from rpc_xprt_ops
  sunrpc: replace svc_serv->sv_bc_xprt by boolean flag
  sunrpc: use-after-free in svc_process_common()
  sunrpc: use SVC_NET() in svcauth_gss_* functions
  nfsd: drop useless LIST_HEAD
  lockd: Show pid of lockd for remote locks
  NFSD remove OP_CACHEME from 4.2 op_flags
  nfsd: Return EPERM, not EACCES, in some SETATTR cases
  sunrpc: fix cache_head leak due to queued request
  nfsd: clean up indentation, increase indentation in switch statement
  svcrdma: Optimize the logic that selects the R_key to invalidate
  nfsd: fix a warning in __cld_pipe_upcall()
  nfsd4: fix crash on writing v4_end_grace before nfsd startup
  ...

Daniel Borkmann says:

====================
This set fixes an out of bounds case under speculative execution
by implementing masking of pointer alu into the verifier. For
details please see the individual patches.

Thanks!

v2 -> v3:
  - 8/9: change states_equal condition into old->speculative &&
    !cur->speculative, thanks Jakub!
  - 8/9: remove incorrect speculative state test in
    propagate_liveness(), thanks Jakub!
v1 -> v2:
  - Typo fixes in commit msg and a comment, thanks David!
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add various map value pointer related test cases to test_verifier
kselftest to reflect recent changes and improve test coverage. The
tests include basic masking functionality, unprivileged behavior
on pointer arithmetic which goes oob, mixed bounds tests, negative
unknown scalar but resulting positive offset for access and helper
range, handling of arithmetic from multiple maps, various masking
scenarios with subsequent map value access and others including two
test cases from Jann Horn for prior fixes.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Jann reported that the original commit back in b2157399
("bpf: prevent out-of-bounds speculation") was not sufficient
to stop CPU from speculating out of bounds memory access:
While b2157399 only focussed on masking array map access
for unprivileged users for tail calls and data access such
that the user provided index gets sanitized from BPF program
and syscall side, there is still a more generic form affected
from BPF programs that applies to most maps that hold user
data in relation to dynamic map access when dealing with
unknown scalars or "slow" known scalars as access offset, for
example:

  - Load a map value pointer into R6
  - Load an index into R7
  - Do a slow computation (e.g. with a memory dependency) that
    loads a limit into R8 (e.g. load the limit from a map for
    high latency, then mask it to make the verifier happy)
  - Exit if R7 >= R8 (mispredicted branch)
  - Load R0 = R6[R7]
  - Load R0 = R6[R0]

For unknown sca...

In check_map_access() we probe actual bounds through __check_map_access()
with offset of reg->smin_value + off for lower bound and offset of
reg->umax_value + off for the upper bound. However, even though the
reg->smin_value could have a negative value, the final result of the
sum with off could be positive when pointer arithmetic with known and
unknown scalars is combined. In this case we reject the program with
an error such as "R<x> min value is negative, either use unsigned index
or do a if (index >=0) check." even though the access itself would be
fine. Therefore extend the check to probe whether the actual resulting
reg->smin_value + off is less than zero.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

For unknown scalars of mixed signed bounds, meaning their smin_value is
negative and their smax_value is positive, we need to reject arithmetic
with pointer to map value. For unprivileged the goal is to mask every
map pointer arithmetic and this cannot reliably be done when it is
unknown at verification time whether the scalar value is negative or
positive. Given this is a corner case, the likelihood of breaking should
be very small.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Restrict stack pointer arithmetic for unprivileged users in that
arithmetic itself must not go out of bounds as opposed to the actual
access later on. Therefore after each adjust_ptr_min_max_vals() with
a stack pointer as a destination we simulate a check_stack_access()
of 1 byte on the destination and once that fails the program is
rejected for unprivileged program loads. This is analog to map
value pointer arithmetic and needed for masking later on.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Restrict map value pointer arithmetic for unprivileged users in that
arithmetic itself must not go out of bounds as opposed to the actual
access later on. Therefore after each adjust_ptr_min_max_vals() with a
map value pointer as a destination it will simulate a check_map_access()
of 1 byte on the destination and once that fails the program is rejected
for unprivileged program loads. We use this later on for masking any
pointer arithmetic with the remainder of the map value space. The
likelihood of breaking any existing real-world unprivileged eBPF
program is very small for this corner case.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Right now we are using BPF ax register in JIT for constant blinding as
well as in interpreter as temporary variable. Verifier will not be able
to use it simply because its use will get overridden from the former in
bpf_jit_blind_insn(). However, it can be made to work in that blinding
will be skipped if there is prior use in either source or destination
register on the instruction. Taking constraints of ax into account, the
verifier is then open to use it in rewrites under some constraints. Note,
ax register already has mappings in every eBPF JIT.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This change moves the on-stack 64 bit tmp variable in ___bpf_prog_run()
into the hidden ax register. The latter is currently only used in JITs
for constant blinding as a temporary scratch register, meaning the BPF
interpreter will never see the use of ax. Therefore it is safe to use
it for the cases where tmp has been used earlier. This is needed to later
on allow restricted hidden use of ax in both interpreter and JITs.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Move prev_insn_idx and insn_idx from the do_check() function into
the verifier environment, so they can be read inside the various
helper functions for handling the instructions. It's easier to put
this into the environment rather than changing all call-sites only
to pass it along. insn_idx is useful in particular since this later
on allows to hold state in env->insn_aux_data[env->insn_idx].

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Pull 9p updates from Dominique Martinet:
 "Missing prototype warning fix and a syzkaller fix when a 9p server
  advertises a too small msize"

* tag '9p-for-4.21' of git://github.com/martinetd/linux:
  9p/net: put a lower bound on msize
  net/9p: include trans_common.h to fix missing prototype warning.

Pull cifs updates from Steve French:

 - four fixes for stable

 - improvements to DFS including allowing failover to alternate targets

 - some small performance improvements

* tag '4.21-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6: (39 commits)
  cifs: update internal module version number
  cifs: we can not use small padding iovs together with encryption
  cifs: Minor Kconfig clarification
  cifs: Always resolve hostname before reconnecting
  cifs: Add support for failover in cifs_reconnect_tcon()
  cifs: Add support for failover in smb2_reconnect()
  cifs: Only free DFS target list if we actually got one
  cifs: start DFS cache refresher in cifs_mount()
  cifs: Use GFP_ATOMIC when a lock is held in cifs_mount()
  cifs: Add support for failover in cifs_reconnect()
  cifs: Add support for failover in cifs_mount()
  cifs: remove set but not used variable 'sep'
  cifs: Make use of DFS cache to get new DFS referrals
  cifs: minor updates to documentation
  cifs: check kzalloc return
  cifs: remove set but not used variable 'server'
  cifs: Use kzfree() to free password
  cifs: Fix to use kmem_cache_free() instead of kfree()
  cifs: update for current_kernel_time64() removal
  cifs: Add DFS cache routines
  ...

Pull TPM updates from James Morris:

 - Support for partial reads of /dev/tpm0.

 - Clean up for TPM 1.x code: move the commands to tpm1-cmd.c and make
   everything to use the same data structure for building TPM commands
   i.e. struct tpm_buf.

* 'next-tpm' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (25 commits)
  tpm: add support for partial reads
  tpm: tpm_ibmvtpm: fix kdoc warnings
  tpm: fix kdoc for tpm2_flush_context_cmd()
  tpm: tpm_try_transmit() refactor error flow.
  tpm: use u32 instead of int for PCR index
  tpm1: reimplement tpm1_continue_selftest() using tpm_buf
  tpm1: reimplement SAVESTATE using tpm_buf
  tpm1: rename tpm1_pcr_read_dev to tpm1_pcr_read()
  tpm1: implement tpm1_pcr_read_dev() using tpm_buf structure
  tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure
  tpm: tpm-space.c remove unneeded semicolon
  tpm: tpm-interface.c drop unused macros...

Pull smack updates from James Morris:
 "Two Smack patches for 4.21.

  Jose's patch adds missing documentation and Zoran's fleshes out the
  access checks on keyrings"

* 'next-smack' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  Smack: Improve Documentation
  smack: fix access permissions for keyring

This mostly reverts commit 849a3700

 ("block: avoid ordered task
state change for polled IO").  It was wrongly claiming that the ordering
wasn't necessary.  The memory barrier _is_ necessary.

If something is truly polling and not going to sleep, it's the whole
state setting that is unnecessary, not the memory barrier.  Whenever you
set your state to a sleeping state, you absolutely need the memory
barrier.

Note that sometimes the memory barrier can be elsewhere.  For example,
the ordering might be provided by an external lock, or by setting the
process state to sleeping before adding yourself to the wait queue list
that is used for waking up (where the wait queue lock itself will
guarantee that any wakeup will correctly see the sleeping state).

But none of those cases were true here.

NOTE! Some of the polling paths may indeed be able to drop the state
setting entirely, at which point the memory barrier also goes away.

(Also note that this doesn't revert the TASK_RUNNING cases: there is no
race between a wakeup and setting the process state to TASK_RUNNING,
since the end result doesn't depend on ordering).

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>