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* [glibc] posix: Fix -Warray-bounds instances building timer_create [BZ #26687]
@ 2020-10-06 18:32 Adhemerval Zanella
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From: Adhemerval Zanella @ 2020-10-06 18:32 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed
commit 7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon Oct 5 17:30:05 2020 -0300
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.
Diff:
---
sysdeps/unix/sysv/linux/kernel-posix-timers.h | 52 ++++++++++++++----
sysdeps/unix/sysv/linux/timer_create.c | 74 ++++++++------------------
sysdeps/unix/sysv/linux/timer_delete.c | 15 +++---
sysdeps/unix/sysv/linux/timer_getoverr.c | 8 +--
sysdeps/unix/sysv/linux/timer_gettime.c | 6 +--
sysdeps/unix/sysv/linux/timer_settime.c | 8 +--
sysdeps/unix/sysv/linux/x86_64/timer_gettime.c | 4 +-
sysdeps/unix/sysv/linux/x86_64/timer_settime.c | 5 +-
8 files changed, 83 insertions(+), 89 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/kernel-posix-timers.h b/sysdeps/unix/sysv/linux/kernel-posix-timers.h
index 4f8d97d3de..6d22b2b0b3 100644
--- a/sysdeps/unix/sysv/linux/kernel-posix-timers.h
+++ b/sysdeps/unix/sysv/linux/kernel-posix-timers.h
@@ -43,21 +43,11 @@ extern pthread_mutex_t __active_timer_sigev_thread_lock attribute_hidden;
/* Type of timers in the kernel. */
typedef int kernel_timer_t;
-
-/* Internal representation of timer. */
+/* Internal representation of SIGEV_THREAD timer. */
struct timer
{
- /* Notification mechanism. */
- int sigev_notify;
-
- /* Timer ID returned by the kernel. */
kernel_timer_t ktimerid;
- /* All new elements must be added after ktimerid. And if the thrfunc
- element is not the third element anymore the memory allocation in
- timer_create needs to be changed. */
-
- /* Parameters for the thread to be started for SIGEV_THREAD. */
void (*thrfunc) (sigval_t);
sigval_t sival;
pthread_attr_t attr;
@@ -65,3 +55,43 @@ struct timer
/* Next element in list of active SIGEV_THREAD timers. */
struct timer *next;
};
+
+
+/* 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 the MSB bit of the returned
+ 'timer_t' to indicate the timer handles a SIGEV_THREAD. */
+
+static inline timer_t
+kernel_timer_to_timerid (kernel_timer_t ktimerid)
+{
+ return (timer_t) ((intptr_t) ktimerid);
+}
+
+static inline timer_t
+timer_to_timerid (struct timer *ptr)
+{
+ return (timer_t) (INTPTR_MIN | (uintptr_t) ptr >> 1);
+}
+
+static inline bool
+timer_is_sigev_thread (timer_t timerid)
+{
+ return (intptr_t) timerid < 0;
+}
+
+static inline struct timer *
+timerid_to_timer (timer_t timerid)
+{
+ return (struct timer *)((uintptr_t) timerid << 1);
+}
+
+static inline kernel_timer_t
+timerid_to_kernel_timer (timer_t timerid)
+{
+ if (timer_is_sigev_thread (timerid))
+ return timerid_to_timer (timerid)->ktimerid;
+ else
+ return (kernel_timer_t) ((uintptr_t) timerid);
+}
diff --git a/sysdeps/unix/sysv/linux/timer_create.c b/sysdeps/unix/sysv/linux/timer_create.c
index 370c99a517..18fb00c6e6 100644
--- a/sysdeps/unix/sysv/linux/timer_create.c
+++ b/sysdeps/unix/sysv/linux/timer_create.c
@@ -52,16 +52,6 @@ timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
{
struct sigevent local_evp;
- /* We avoid allocating too much memory by basically
- using struct timer as a derived class with the
- first two elements being in the superclass. We only
- need these two elements here. */
- struct timer *newp = (struct timer *) malloc (offsetof (struct timer,
- thrfunc));
- if (newp == NULL)
- /* No more memory. */
- return -1;
-
if (evp == NULL)
{
/* The kernel has to pass up the timer ID which is a
@@ -69,31 +59,17 @@ timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
the kernel to determine it. */
local_evp.sigev_notify = SIGEV_SIGNAL;
local_evp.sigev_signo = SIGALRM;
- local_evp.sigev_value.sival_ptr = newp;
+ local_evp.sigev_value.sival_ptr = NULL;
evp = &local_evp;
}
kernel_timer_t ktimerid;
- int retval = INLINE_SYSCALL (timer_create, 3, syscall_clockid, evp,
- &ktimerid);
-
- if (retval != -1)
- {
- newp->sigev_notify = (evp != NULL
- ? evp->sigev_notify : SIGEV_SIGNAL);
- newp->ktimerid = ktimerid;
-
- *timerid = (timer_t) newp;
- }
- else
- {
- /* Cannot allocate the timer, fail. */
- free (newp);
- retval = -1;
- }
+ if (INLINE_SYSCALL_CALL (timer_create, syscall_clockid, evp,
+ &ktimerid) == -1)
+ return -1;
- return retval;
+ *timerid = kernel_timer_to_timerid (ktimerid);
}
else
{
@@ -106,20 +82,18 @@ timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
return -1;
}
- struct timer *newp;
- newp = (struct timer *) malloc (sizeof (struct timer));
+ struct timer *newp = malloc (sizeof (struct timer));
if (newp == NULL)
return -1;
/* Copy the thread parameters the user provided. */
newp->sival = evp->sigev_value;
newp->thrfunc = evp->sigev_notify_function;
- newp->sigev_notify = SIGEV_THREAD;
/* We cannot simply copy the thread attributes since the
implementation might keep internal information for
each instance. */
- (void) pthread_attr_init (&newp->attr);
+ pthread_attr_init (&newp->attr);
if (evp->sigev_notify_attributes != NULL)
{
struct pthread_attr *nattr;
@@ -137,8 +111,7 @@ timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
}
/* In any case set the detach flag. */
- (void) pthread_attr_setdetachstate (&newp->attr,
- PTHREAD_CREATE_DETACHED);
+ pthread_attr_setdetachstate (&newp->attr, PTHREAD_CREATE_DETACHED);
/* Create the event structure for the kernel timer. */
struct sigevent sev =
@@ -149,27 +122,24 @@ timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
/* Create the timer. */
int res;
- res = INTERNAL_SYSCALL_CALL (timer_create,
- syscall_clockid, &sev, &newp->ktimerid);
- if (! INTERNAL_SYSCALL_ERROR_P (res))
+ res = INTERNAL_SYSCALL_CALL (timer_create, syscall_clockid, &sev,
+ &newp->ktimerid);
+ if (INTERNAL_SYSCALL_ERROR_P (res))
{
- /* Add to the queue of active timers with thread
- delivery. */
- pthread_mutex_lock (&__active_timer_sigev_thread_lock);
- newp->next = __active_timer_sigev_thread;
- __active_timer_sigev_thread = newp;
- pthread_mutex_unlock (&__active_timer_sigev_thread_lock);
-
- *timerid = (timer_t) newp;
- return 0;
+ free (newp);
+ __set_errno (INTERNAL_SYSCALL_ERRNO (res));
+ return -1;
}
- /* Free the resources. */
- free (newp);
-
- __set_errno (INTERNAL_SYSCALL_ERRNO (res));
+ /* Add to the queue of active timers with thread delivery. */
+ pthread_mutex_lock (&__active_timer_sigev_thread_lock);
+ newp->next = __active_timer_sigev_thread;
+ __active_timer_sigev_thread = newp;
+ pthread_mutex_unlock (&__active_timer_sigev_thread_lock);
- return -1;
+ *timerid = timer_to_timerid (newp);
}
}
+
+ return 0;
}
diff --git a/sysdeps/unix/sysv/linux/timer_delete.c b/sysdeps/unix/sysv/linux/timer_delete.c
index c240c06139..c8a5f101b4 100644
--- a/sysdeps/unix/sysv/linux/timer_delete.c
+++ b/sysdeps/unix/sysv/linux/timer_delete.c
@@ -32,15 +32,15 @@ int
timer_delete (timer_t timerid)
{
#undef timer_delete
- struct timer *kt = (struct timer *) timerid;
-
- /* Delete the kernel timer object. */
- int res = INLINE_SYSCALL (timer_delete, 1, kt->ktimerid);
+ kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
+ int res = INLINE_SYSCALL_CALL (timer_delete, ktimerid);
if (res == 0)
{
- if (kt->sigev_notify == SIGEV_THREAD)
+ if (timer_is_sigev_thread (timerid))
{
+ struct timer *kt = timerid_to_timer (timerid);
+
/* Remove the timer from the list. */
pthread_mutex_lock (&__active_timer_sigev_thread_lock);
if (__active_timer_sigev_thread == kt)
@@ -58,10 +58,9 @@ timer_delete (timer_t timerid)
prevp = prevp->next;
}
pthread_mutex_unlock (&__active_timer_sigev_thread_lock);
- }
- /* Free the memory. */
- (void) free (kt);
+ free (kt);
+ }
return 0;
}
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);
}
diff --git a/sysdeps/unix/sysv/linux/timer_gettime.c b/sysdeps/unix/sysv/linux/timer_gettime.c
index 5d31c7c864..07b6309ba9 100644
--- a/sysdeps/unix/sysv/linux/timer_gettime.c
+++ b/sysdeps/unix/sysv/linux/timer_gettime.c
@@ -26,18 +26,18 @@
int
__timer_gettime64 (timer_t timerid, struct __itimerspec64 *value)
{
- struct timer *kt = (struct timer *) timerid;
+ kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
#ifndef __NR_timer_gettime64
# define __NR_timer_gettime64 __NR_timer_gettime
#endif
- int ret = INLINE_SYSCALL_CALL (timer_gettime64, kt->ktimerid, value);
+ int ret = INLINE_SYSCALL_CALL (timer_gettime64, ktimerid, value);
#ifndef __ASSUME_TIME64_SYSCALLS
if (ret == 0 || errno != ENOSYS)
return ret;
struct itimerspec its32;
- ret = INLINE_SYSCALL_CALL (timer_gettime, kt->ktimerid, &its32);
+ ret = INLINE_SYSCALL_CALL (timer_gettime, ktimerid, &its32);
if (ret == 0)
{
value->it_interval = valid_timespec_to_timespec64 (its32.it_interval);
diff --git a/sysdeps/unix/sysv/linux/timer_settime.c b/sysdeps/unix/sysv/linux/timer_settime.c
index c97a9e92ef..01c6257938 100644
--- a/sysdeps/unix/sysv/linux/timer_settime.c
+++ b/sysdeps/unix/sysv/linux/timer_settime.c
@@ -28,17 +28,17 @@ __timer_settime64 (timer_t timerid, int flags,
const struct __itimerspec64 *value,
struct __itimerspec64 *ovalue)
{
- struct timer *kt = (struct timer *) timerid;
+ kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
#ifdef __ASSUME_TIME64_SYSCALLS
# ifndef __NR_timer_settime64
# define __NR_timer_settime64 __NR_timer_settime
# endif
- return INLINE_SYSCALL_CALL (timer_settime64, kt->ktimerid, flags, value,
+ return INLINE_SYSCALL_CALL (timer_settime64, ktimerid, flags, value,
ovalue);
#else
# ifdef __NR_timer_settime64
- int ret = INLINE_SYSCALL_CALL (timer_settime64, kt->ktimerid, flags, value,
+ int ret = INLINE_SYSCALL_CALL (timer_settime64, ktimerid, flags, value,
ovalue);
if (ret == 0 || errno != ENOSYS)
return ret;
@@ -55,7 +55,7 @@ __timer_settime64 (timer_t timerid, int flags,
its32.it_interval = valid_timespec64_to_timespec (value->it_interval);
its32.it_value = valid_timespec64_to_timespec (value->it_value);
- int retval = INLINE_SYSCALL_CALL (timer_settime, kt->ktimerid, flags,
+ int retval = INLINE_SYSCALL_CALL (timer_settime, ktimerid, flags,
&its32, ovalue ? &oits32 : NULL);
if (retval == 0 && ovalue)
{
diff --git a/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c b/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c
index 89002c7243..0e4213d7aa 100644
--- a/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c
+++ b/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c
@@ -24,9 +24,9 @@
int
__timer_gettime_new (timer_t timerid, struct itimerspec *value)
{
- struct timer *kt = (struct timer *) timerid;
+ kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
- return INLINE_SYSCALL_CALL (timer_gettime, kt->ktimerid, value);
+ return INLINE_SYSCALL_CALL (timer_gettime, ktimerid, value);
}
versioned_symbol (librt, __timer_gettime_new, timer_gettime, GLIBC_2_3_3);
diff --git a/sysdeps/unix/sysv/linux/x86_64/timer_settime.c b/sysdeps/unix/sysv/linux/x86_64/timer_settime.c
index 7af417459e..0636f7316d 100644
--- a/sysdeps/unix/sysv/linux/x86_64/timer_settime.c
+++ b/sysdeps/unix/sysv/linux/x86_64/timer_settime.c
@@ -25,10 +25,9 @@ int
__timer_settime_new (timer_t timerid, int flags, const struct itimerspec *value,
struct itimerspec *ovalue)
{
- struct timer *kt = (struct timer *) timerid;
+ kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
- return INLINE_SYSCALL_CALL (timer_settime, kt->ktimerid, flags, value,
- ovalue);
+ return INLINE_SYSCALL_CALL (timer_settime, ktimerid, flags, value, ovalue);
}
versioned_symbol (librt, __timer_settime_new, timer_settime, GLIBC_2_3_3);
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