* [PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache
@ 2024-02-05 5:54 Tom de Vries
2024-02-05 8:34 ` Luis Machado
0 siblings, 1 reply; 5+ messages in thread
From: Tom de Vries @ 2024-02-05 5:54 UTC (permalink / raw)
To: gdb-patches
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
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache
2024-02-05 5:54 [PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache Tom de Vries
@ 2024-02-05 8:34 ` Luis Machado
2024-02-05 18:49 ` Thiago Jung Bauermann
0 siblings, 1 reply; 5+ messages in thread
From: Luis Machado @ 2024-02-05 8:34 UTC (permalink / raw)
To: Tom de Vries, gdb-patches
On 2/5/24 05:54, Tom de Vries wrote:
> 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
Looks like I missed a spot in the per-bfd conversion there.
Thanks Thiago and Tom for the investigation and fix. This is OK.
Approved-By: Luis Machado <luis.machado@arm.com>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache
2024-02-05 8:34 ` Luis Machado
@ 2024-02-05 18:49 ` Thiago Jung Bauermann
2024-02-05 20:24 ` Tom Tromey
0 siblings, 1 reply; 5+ messages in thread
From: Thiago Jung Bauermann @ 2024-02-05 18:49 UTC (permalink / raw)
To: Luis Machado; +Cc: Tom de Vries, gdb-patches
Luis Machado <luis.machado@arm.com> writes:
> On 2/5/24 05:54, Tom de Vries wrote:
>> 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
>
> Looks like I missed a spot in the per-bfd conversion there.
>
> Thanks Thiago and Tom for the investigation and fix. This is OK.
>
> Approved-By: Luis Machado <luis.machado@arm.com>
Could this patch also be committed to the GDB 14 branch?
--
Thiago
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache
2024-02-05 18:49 ` Thiago Jung Bauermann
@ 2024-02-05 20:24 ` Tom Tromey
2024-02-06 21:35 ` Thiago Jung Bauermann
0 siblings, 1 reply; 5+ messages in thread
From: Tom Tromey @ 2024-02-05 20:24 UTC (permalink / raw)
To: Thiago Jung Bauermann; +Cc: Luis Machado, Tom de Vries, gdb-patches
>>>>> "Thiago" == Thiago Jung Bauermann <thiago.bauermann@linaro.org> writes:
>> Looks like I missed a spot in the per-bfd conversion there.
>>
>> Thanks Thiago and Tom for the investigation and fix. This is OK.
>>
>> Approved-By: Luis Machado <luis.machado@arm.com>
Thiago> Could this patch also be committed to the GDB 14 branch?
I think it's fine.
Tom
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache
2024-02-05 20:24 ` Tom Tromey
@ 2024-02-06 21:35 ` Thiago Jung Bauermann
0 siblings, 0 replies; 5+ messages in thread
From: Thiago Jung Bauermann @ 2024-02-06 21:35 UTC (permalink / raw)
To: Tom Tromey; +Cc: Luis Machado, Tom de Vries, gdb-patches
Tom Tromey <tom@tromey.com> writes:
>>>>>> "Thiago" == Thiago Jung Bauermann <thiago.bauermann@linaro.org> writes:
>
>>> Looks like I missed a spot in the per-bfd conversion there.
>>>
>>> Thanks Thiago and Tom for the investigation and fix. This is OK.
>>>
>>> Approved-By: Luis Machado <luis.machado@arm.com>
>
> Thiago> Could this patch also be committed to the GDB 14 branch?
>
> I think it's fine.
Thanks! I just pushed it to the branch as commit 7c709b26ba13.
--
Thiago
^ permalink raw reply [flat|nested] 5+ messages in thread
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2024-02-05 5:54 [PATCH] [gdb/tdep] Fix use-after-free in arm_exidx_fill_cache Tom de Vries
2024-02-05 8:34 ` Luis Machado
2024-02-05 18:49 ` Thiago Jung Bauermann
2024-02-05 20:24 ` Tom Tromey
2024-02-06 21:35 ` Thiago Jung Bauermann
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