signal: Prevent double-free of user struct
The way user struct reference counting works changed significantly with, fda31c50292a ("signal: avoid double atomic counter increments for user accounting") Now user structs are only freed once the last pending signal is dequeued. Make sigqueue_free_current() follow this new convention to avoid freeing the user struct multiple times and triggering this warning: refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 6794 at lib/refcount.c:288 refcount_dec_not_one+0x45/0x50 Call Trace: refcount_dec_and_lock_irqsave+0x16/0x60 free_uid+0x31/0xa0 __dequeue_signal+0x17c/0x190 dequeue_signal+0x5a/0x1b0 do_sigtimedwait+0x208/0x250 __x64_sys_rt_sigtimedwait+0x6f/0xd0 do_syscall_64+0x72/0x200 entry_SYSCALL_64_after_hwframe+0x49/0xbe Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> Reported-by: Daniel Wagner <wagi@monom.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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@ -495,8 +495,8 @@ static void sigqueue_free_current(struct sigqueue *q)
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up = q->user;
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if (rt_prio(current->normal_prio) && !put_task_cache(current, q)) {
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atomic_dec(&up->sigpending);
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free_uid(up);
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if (atomic_dec_and_test(&up->sigpending))
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free_uid(up);
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} else
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__sigqueue_free(q);
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}
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