[PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache
Tom de Vries
tdevries@suse.de
Mon Feb 5 05:54:40 GMT 2024
On arm-linux the linaro CI occasionally reports:
...
(gdb) up 10
#4 0x0001b864 in pthread_join ()
(gdb) FAIL: gdb.threads/staticthreads.exp: up 10
...
while this is expected:
...
(gdb) up 10
#3 0x00010568 in main (argc=1, argv=0xfffeede4) at staticthreads.c:76
76 pthread_join (thread, NULL);
(gdb) PASS: gdb.threads/staticthreads.exp: up 10
...
Thiago investigated the problem, and using valgrind found an invalid read in
arm_exidx_fill_cache.
The problem happens as follows:
- an objfile and corresponding per_bfd are allocated
- some memory is allocated in arm_exidx_new_objfile using
objfile->objfile_obstack, for the "exception table entry cache".
- a symbol reread is triggered, and the objfile, including the
objfile_obstack, is destroyed
- a new objfile is allocated, using the same per_bfd
- again arm_exidx_new_objfile is called, but since the same per_bfd is used,
it doesn't allocate any new memory for the "exception table entry cache".
- the "exception table entry cache" is accessed by arm_exidx_fill_cache,
and we have a use-after-free.
This is a regression since commit a2726d4ff80 ("[ARM] Store exception handling
information per-bfd instead of per-objfile"), which changed the "exception
table entry cache" from per-objfile to per-bfd, but failed to update the
obstack_alloc.
Fix this by using objfile->per_bfd->storage_obstack instead of
objfile->objfile_obstack.
I couldn't reproduce the FAIL myself, but Thiago confirmed that the patch
fixes it.
Tested on arm-linux.
PR tdep/31254
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31254
---
gdb/arm-tdep.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 0d0431e0d1c..861d50a6a3b 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -2701,7 +2701,7 @@ arm_exidx_new_objfile (struct objfile *objfile)
if (n_bytes || n_words)
{
gdb_byte *p = entry
- = (gdb_byte *) obstack_alloc (&objfile->objfile_obstack,
+ = (gdb_byte *) obstack_alloc (&objfile->per_bfd->storage_obstack,
n_bytes + n_words * 4 + 1);
while (n_bytes--)
base-commit: 029e52bac7f3a6dd8b39f7f3d298b73174da806b
--
2.35.3
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