Petr Mladek 78f5009cc3 ipc/sem.c: avoid overflow of semop undo (semadj) value ... When trying to understand semop code, I found a small mistake in the check for semadj (undo) value overflow. The new undo value is not stored immediately and next potential checks are done against the old value. The failing scenario is not much practical. One semop call has to do more operations on the same semaphore. Also semval and semadj must have different values, so there has to be some operations without SEM_UNDO flag. For example: struct sembuf depositor_op[1]; struct sembuf collector_op[2]; depositor_op[0].sem_num = 0; depositor_op[0].sem_op = 20000; depositor_op[0].sem_flg = 0; collector_op[0].sem_num = 0; collector_op[0].sem_op = -10000; collector_op[0].sem_flg = SEM_UNDO; collector_op[1].sem_num = 0; collector_op[1].sem_op = -10000; collector_op[1].sem_flg = SEM_UNDO; if (semop(semid, depositor_op, 1) == -1) { perror("Failed to do 1st deposit"); return 1; } if (semop(semid, collector_op, 2) == -1) { perror("Failed to do 1st collect"); return 1; } if (semop(semid, depositor_op, 1) == -1) { perror("Failed to do 2nd deposit"); return 1; } if (semop(semid, collector_op, 2) == -1) { perror("Failed to do 2nd collect"); return 1; } return 0; It passes without error now but the semadj value has overflown in the 2nd collector operation. [akpm@linux-foundation.org: restore lessened scope of local `undo'] [davidlohr@hp.com: correct header comment for perform_atomic_semop] Signed-off-by: Petr Mladek <pmladek@suse.cz> Acked-by: Davidlohr Bueso <davidlohr@hp.com> Acked-by: Manfred Spraul <manfred@colorfullife.com> Cc: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2014-01-27 21:02:39 -08:00
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compat_mq.c	ipc: initialize structure memory to zero for compat functions	2010-10-27 18:03:13 -07:00
compat.c	get rid of union semop in sys_semctl(2) arguments	2013-03-05 15:14:16 -05:00
ipc_sysctl.c	ipc, msg: forbid negative values for "msg{max,mnb,mni}"	2013-11-03 10:53:11 -08:00
ipcns_notifier.c	ipc: do not use a negative value to re-enable msgmni automatic recomputing	2008-07-25 10:53:42 -07:00
Makefile	Add generic sys_ipc wrapper	2010-03-12 15:52:32 -08:00
mq_sysctl.c	mqueue: separate mqueue default value from maximum value	2012-05-31 17:49:31 -07:00
mqueue.c	locks: break delegations on unlink	2013-11-09 00:16:42 -05:00
msg.c	ipc,msg: prevent race with rmid in msgsnd,msgrcv	2013-09-30 14:31:03 -07:00
msgutil.c	ipc, msg: fix message length check for negative values	2013-11-13 12:09:36 +09:00
namespace.c	ipc: drop ipc_lock_by_ptr	2013-09-11 15:59:44 -07:00
sem.c	ipc/sem.c: avoid overflow of semop undo (semadj) value	2014-01-27 21:02:39 -08:00
shm.c	ipc,shm: correct error return value in shmctl (SHM_UNLOCK)	2013-11-21 16:42:28 -08:00
syscall.c	get rid of union semop in sys_semctl(2) arguments	2013-03-05 15:14:16 -05:00
util.c	ipc/util.c: remove unnecessary work pending test	2013-11-13 12:09:36 +09:00
util.h	ipc, msg: fix message length check for negative values	2013-11-13 12:09:36 +09:00