* [committed 2.35] fortify: Ensure that __glibc_fortify condition is a constant [BZ #29141]
@ 2022-05-16 16:10 Siddhesh Poyarekar
2022-05-16 16:38 ` Siddhesh Poyarekar
0 siblings, 1 reply; 2+ messages in thread
From: Siddhesh Poyarekar @ 2022-05-16 16:10 UTC (permalink / raw)
To: libc-stable
The fix c8ee1c85 introduced a -1 check for object size without also
checking that object size is a constant. Because of this, the tree
optimizer passes in gcc fail to fold away one of the branches in
__glibc_fortify and trips on a spurious Wstringop-overflow. The warning
itself is incorrect and the branch does go away eventually in DCE in the
rtl passes in gcc, but the constant check is a helpful hint to simplify
code early, so add it in.
Resolves: BZ #29141
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
misc/sys/cdefs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
index f1faf8292c..1c2b044a0d 100644
--- a/misc/sys/cdefs.h
+++ b/misc/sys/cdefs.h
@@ -164,7 +164,7 @@
/* Length is known to be safe at compile time if the __L * __S <= __OBJSZ
condition can be folded to a constant and if it is true, or unknown (-1) */
#define __glibc_safe_or_unknown_len(__l, __s, __osz) \
- ((__osz) == (__SIZE_TYPE__) -1 \
+ ((__builtin_constant_p (__osz) && (__osz) == (__SIZE_TYPE__) -1) \
|| (__glibc_unsigned_or_positive (__l) \
&& __builtin_constant_p (__glibc_safe_len_cond ((__SIZE_TYPE__) (__l), \
(__s), (__osz))) \
--
2.35.1
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [committed 2.35] fortify: Ensure that __glibc_fortify condition is a constant [BZ #29141]
2022-05-16 16:10 [committed 2.35] fortify: Ensure that __glibc_fortify condition is a constant [BZ #29141] Siddhesh Poyarekar
@ 2022-05-16 16:38 ` Siddhesh Poyarekar
0 siblings, 0 replies; 2+ messages in thread
From: Siddhesh Poyarekar @ 2022-05-16 16:38 UTC (permalink / raw)
To: libc-stable
On 16/05/2022 21:40, Siddhesh Poyarekar via Libc-stable wrote:
> The fix c8ee1c85 introduced a -1 check for object size without also
> checking that object size is a constant. Because of this, the tree
> optimizer passes in gcc fail to fold away one of the branches in
> __glibc_fortify and trips on a spurious Wstringop-overflow. The warning
> itself is incorrect and the branch does go away eventually in DCE in the
> rtl passes in gcc, but the constant check is a helpful hint to simplify
> code early, so add it in.
>
> Resolves: BZ #29141
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Ugh, I'm so sorry, I forgot to use -x :(
We should have a commit hook that rejects patches on release branches
without the "cherry picked from".
Siddhesh
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2022-05-16 16:10 [committed 2.35] fortify: Ensure that __glibc_fortify condition is a constant [BZ #29141] Siddhesh Poyarekar
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