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| author | Pedro Alves <palves@redhat.com> | 2013-03-07 09:47:57 +0000 |
|---|---|---|
| committer | Pedro Alves <palves@redhat.com> | 2013-03-07 09:47:57 +0000 |
| commit | f0ae6fc35c1c1e21a19e5f19f0177858ea180771 (patch) | |
| tree | 5a82927e5a55635d7217794bd07afdf9f5d33456 | |
| parent | 02e60bf7bab71c3850f2b525db079a0309140689 (diff) | |
| download | gdb-f0ae6fc35c1c1e21a19e5f19f0177858ea180771.zip gdb-f0ae6fc35c1c1e21a19e5f19f0177858ea180771.tar.gz gdb-f0ae6fc35c1c1e21a19e5f19f0177858ea180771.tar.bz2 | |
PR gdb/15236: gdbserver write to linux memory with zero length corrupts stack
PROBLEM:
The function linux_write_memory () in linux-low.c allocates a buffer
on the stack to hold a copy of the data to be written.
register PTRACE_XFER_TYPE *buffer = (PTRACE_XFER_TYPE *)
alloca (count * sizeof (PTRACE_XFER_TYPE));
"count" is the number of bytes to be written, rounded up to the
nearest multiple of sizeof (PTRACE_XFER_TYPE) and allowing for not
being an aligned address. The function later uses
buffer[0] = ptrace (PTRACE_PEEKTEXT, pid,
(PTRACE_ARG3_TYPE) (uintptr_t) addr, 0);
The problem is that this function can be called to write zero bytes on
an aligned address, for example when receiving an X packet of length 0
(used to test if 8-bit write is supported). Under these circumstances,
count can be zero.
Since in this case, buffer[0] may never have been allocated, the stack
is corrupted and gdbserver may crash.
SOLUTION:
Writing zero bytes should always succeed. The patch below returns
successfully early if the length is zero, so avoiding the stack
corruption.
Verified on the ARC GDB 7.5.1 port.
2013-03-07 Jeremy Bennett <jeremy.bennett@embecosm.com>
PR server/15236
* linux-low.c (linux_write_memory): Return early success if LEN is
zero.
| -rw-r--r-- | gdb/gdbserver/ChangeLog | 6 | ||||
| -rw-r--r-- | gdb/gdbserver/linux-low.c | 8 |
2 files changed, 13 insertions, 1 deletions
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index a8cf78c..67bc149 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,9 @@ +2013-03-07 Jeremy Bennett <jeremy.bennett@embecosm.com> + + PR server/15236 + * linux-low.c (linux_write_memory): Return early success if LEN is + zero. + 2013-03-05 Corinna Vinschen <vinschen@redhat.de> * configure.srv: Add x86_64-*-cygwin* as target. diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c index c52cd2e..5f03628 100644 --- a/gdb/gdbserver/linux-low.c +++ b/gdb/gdbserver/linux-low.c @@ -4481,7 +4481,7 @@ linux_read_memory (CORE_ADDR memaddr, unsigned char *myaddr, int len) /* Copy LEN bytes of data from debugger memory at MYADDR to inferior's memory at MEMADDR. On failure (cannot write to the inferior) - returns the value of errno. */ + returns the value of errno. Always succeeds if LEN is zero. */ static int linux_write_memory (CORE_ADDR memaddr, const unsigned char *myaddr, int len) @@ -4500,6 +4500,12 @@ linux_write_memory (CORE_ADDR memaddr, const unsigned char *myaddr, int len) int pid = lwpid_of (get_thread_lwp (current_inferior)); + if (len == 0) + { + /* Zero length write always succeeds. */ + return 0; + } + if (debug_threads) { /* Dump up to four bytes. */ |