From 7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed Mon Sep 17 00:00:00 2001
From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon, 5 Oct 2020 17:30:05 -0300
Subject: posix: Fix -Warray-bounds instances building timer_create [BZ #26687]
GCC 11 -Warray-bounds triggers invalid warnings when building
Linux timer_create.c:
../sysdeps/unix/sysv/linux/timer_create.c: In function '__timer_create_new':
../sysdeps/unix/sysv/linux/timer_create.c:83:17: warning: array subscript 'struct timer[0]' is partly outside array bounds of 'unsigned char[8]' [-Warray-bounds]
83 | newp->sigev_notify = (evp != NULL
| ^~
../sysdeps/unix/sysv/linux/timer_create.c:59:47: note: referencing an object of size 8 allocated by 'malloc'
59 | struct timer *newp = (struct timer *) malloc (offsetof (struct timer,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
60 | thrfunc));
| ~~~~~~~~~
The struct allocated for !SIGEV_THREAD timers only requires two 'int'
fields (sigev_notify and ktimerid) and the offsetof trick tries minimize
the memory usage by only allocation the required size. However,
although the resulting size is suffice for !SIGEV_THREAD time, accessing
the partially allocated object is error-prone and UB.
This patch fixes both issues by embedding the information whether
the timer if a SIGEV_THREAD in the returned 'timer_t'. For
!SIGEV_THREAD, the resulting 'timer_t' is the returned kernel timer
identifer (kernel_timer_t), while for SIGEV_THREAD it uses the fact
malloc returns at least _Alignof (max_align_t) pointers plus that
valid kernel_timer_t are always positive to set MSB bit of the returned
'timer_t' to indicate the timer handles a SIGEV_THREAD.
It allows to remove the memory allocation for !SIGEV_THREAD and also
remove the 'sigev_notify' field from 'struct timer'.
Checked on x86_64-linux-gnu and i686-linux-gnu.
---
sysdeps/unix/sysv/linux/timer_getoverr.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
(limited to 'sysdeps/unix/sysv/linux/timer_getoverr.c')
diff --git a/sysdeps/unix/sysv/linux/timer_getoverr.c b/sysdeps/unix/sysv/linux/timer_getoverr.c
index 81b9723f01..7862d162b9 100644
--- a/sysdeps/unix/sysv/linux/timer_getoverr.c
+++ b/sysdeps/unix/sysv/linux/timer_getoverr.c
@@ -31,10 +31,6 @@ int
timer_getoverrun (timer_t timerid)
{
#undef timer_getoverrun
- struct timer *kt = (struct timer *) timerid;
-
- /* Get the information from the kernel. */
- int res = INLINE_SYSCALL (timer_getoverrun, 1, kt->ktimerid);
-
- return res;
+ kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
+ return INLINE_SYSCALL_CALL (timer_getoverrun, ktimerid);
}
--
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