From 7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella 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_create.c | 74 ++++++++++------------------------ 1 file changed, 22 insertions(+), 52 deletions(-) (limited to 'sysdeps/unix/sysv/linux/timer_create.c') 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; } -- cgit 1.4.1