tjh.dev / kernel
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posix timers: sigqueue_free: don't free sigqueue if it is queued

Currently sigqueue_free() removes sigqueue from list, but doesn't cancel the
pending signal. This is not consistent, the task should either receive the
"full" signal along with siginfo_t, or it shouldn't receive the signal at all.

Change sigqueue_free() to clear SIGQUEUE_PREALLOC but leave sigqueue on list
if it is queued.

This is a user-visible change. If the signal is blocked, it stays queued
after sys_timer_delete() until unblocked with the "stale" si_code/si_value,
and of course it is still counted wrt RLIMIT_SIGPENDING which also limits
the number of posix timers.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Austin Clements <amdragon+kernelbugzilla@mit.edu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

authored by

Oleg Nesterov and committed by
Linus Torvalds c8e85b4f 84a88165

+10 -6
+10 -6
kernel/signal.c
··· 1240 1240 1241 1241 BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); 1242 1242 /* 1243 - * If the signal is still pending remove it from the 1244 - * pending queue. We must hold ->siglock while testing 1245 - * q->list to serialize with collect_signal() or with 1243 + * We must hold ->siglock while testing q->list 1244 + * to serialize with collect_signal() or with 1246 1245 * __exit_signal()->flush_sigqueue(). 1247 1246 */ 1248 1247 spin_lock_irqsave(lock, flags); 1248 + q->flags &= ~SIGQUEUE_PREALLOC; 1249 + /* 1250 + * If it is queued it will be freed when dequeued, 1251 + * like the "regular" sigqueue. 1252 + */ 1249 1253 if (!list_empty(&q->list)) 1250 - list_del_init(&q->list); 1254 + q = NULL; 1251 1255 spin_unlock_irqrestore(lock, flags); 1252 1256 1253 - q->flags &= ~SIGQUEUE_PREALLOC; 1254 - __sigqueue_free(q); 1257 + if (q) 1258 + __sigqueue_free(q); 1255 1259 } 1256 1260 1257 1261 int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)