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authorSergey Bugaev <bugaevc@gmail.com>2023-05-17 22:14:32 +0300
committerSamuel Thibault <samuel.thibault@ens-lyon.org>2023-05-17 22:59:50 +0200
commitc7fcce38c83a2bb665ef5dc4981bf20c7e586123 (patch)
tree5f8c474fc9c8af09835e720f74060b1b1b27d23b
parentaa19c68d2bdf3a831894f609b8ac5c8f123268b2 (diff)
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hurd: Make sure to not use tcb->self
Unlike sigstate->thread, tcb->self did not hold a Mach port reference on the thread port it names. This means that the port can be deallocated, and the name reused for something else, without anyone noticing. Using tcb->self will then lead to port use-after-free. Fortunately nothing was accessing tcb->self, other than it being intially set to then-valid thread port name upon TCB initialization. To assert that this keeps being the case without altering TCB layout, rename self -> self_do_not_use, and stop initializing it. Also, do not (re-)allocate a whole separate and unused stack for the main thread, and just exit __pthread_setup early in this case. Found upon attempting to use tcb->self and getting unexpected crashes. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> Message-Id: <20230517191436.73636-7-bugaevc@gmail.com>
-rw-r--r--sysdeps/mach/hurd/i386/tls.h3
-rw-r--r--sysdeps/mach/hurd/x86/htl/pt-setup.c34
-rw-r--r--sysdeps/mach/hurd/x86_64/tls.h3
3 files changed, 14 insertions, 26 deletions
diff --git a/sysdeps/mach/hurd/i386/tls.h b/sysdeps/mach/hurd/i386/tls.h
index e124fb1..ba28300 100644
--- a/sysdeps/mach/hurd/i386/tls.h
+++ b/sysdeps/mach/hurd/i386/tls.h
@@ -32,7 +32,7 @@ typedef struct
{
void *tcb; /* Points to this structure. */
dtv_t *dtv; /* Vector of pointers to TLS data. */
- thread_t self; /* This thread's control port. */
+ thread_t self_do_not_use; /* This thread's control port. */
int multiple_threads;
uintptr_t sysinfo;
uintptr_t stack_guard;
@@ -419,7 +419,6 @@ _hurd_tls_new (thread_t child, tcbhead_t *tcb)
HURD_TLS_DESC_DECL (desc, tcb);
tcb->tcb = tcb;
- tcb->self = child;
if (HURD_SEL_LDT (sel))
err = __i386_set_ldt (child, sel, &desc, 1);
diff --git a/sysdeps/mach/hurd/x86/htl/pt-setup.c b/sysdeps/mach/hurd/x86/htl/pt-setup.c
index 3abd92b..686124d 100644
--- a/sysdeps/mach/hurd/x86/htl/pt-setup.c
+++ b/sysdeps/mach/hurd/x86/htl/pt-setup.c
@@ -19,6 +19,7 @@
#include <stdint.h>
#include <assert.h>
#include <mach.h>
+#include <hurd.h>
#include <pt-internal.h>
@@ -76,35 +77,24 @@ __pthread_setup (struct __pthread *thread,
void *), void *(*start_routine) (void *),
void *arg)
{
- tcbhead_t *tcb;
error_t err;
- mach_port_t ktid;
- thread->mcontext.pc = entry_point;
- thread->mcontext.sp = stack_setup (thread, start_routine, arg);
-
- ktid = __mach_thread_self ();
- if (thread->kernel_thread == ktid)
+ if (thread->kernel_thread == hurd_thread_self ())
/* Fix up the TCB for the main thread. The C library has already
installed a TCB, which we want to keep using. This TCB must not
be freed so don't register it in the thread structure. On the
other hand, it's not yet possible to reliably release a TCB.
- Leave the unused one registered so that it doesn't leak. The
- only thing left to do is to correctly set the `self' member in
- the already existing TCB. */
- tcb = THREAD_SELF;
- else
- {
- err = __thread_set_pcsptp (thread->kernel_thread,
- 1, thread->mcontext.pc,
- 1, thread->mcontext.sp,
- 1, thread->tcb);
- assert_perror (err);
- tcb = thread->tcb;
- }
- __mach_port_deallocate (__mach_task_self (), ktid);
+ Leave the unused one registered so that it doesn't leak. */
+ return 0;
+
+ thread->mcontext.pc = entry_point;
+ thread->mcontext.sp = stack_setup (thread, start_routine, arg);
- tcb->self = thread->kernel_thread;
+ err = __thread_set_pcsptp (thread->kernel_thread,
+ 1, thread->mcontext.pc,
+ 1, thread->mcontext.sp,
+ 1, thread->tcb);
+ assert_perror (err);
return 0;
}
diff --git a/sysdeps/mach/hurd/x86_64/tls.h b/sysdeps/mach/hurd/x86_64/tls.h
index 1274723..35dcef4 100644
--- a/sysdeps/mach/hurd/x86_64/tls.h
+++ b/sysdeps/mach/hurd/x86_64/tls.h
@@ -35,7 +35,7 @@ typedef struct
{
void *tcb; /* Points to this structure. */
dtv_t *dtv; /* Vector of pointers to TLS data. */
- thread_t self; /* This thread's control port. */
+ thread_t self_do_no_use; /* This thread's control port. */
int __glibc_padding1;
int multiple_threads;
int gscope_flag;
@@ -158,7 +158,6 @@ _hurd_tls_new (thread_t child, tcbhead_t *tcb)
struct i386_fsgs_base_state state;
tcb->tcb = tcb;
- tcb->self = child;
/* Install the TCB address into FS base. */
state.fs_base = (uintptr_t) tcb;