Commit 97abc889 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

signal: remove the wrong signal_pending() check in restore_user_sigmask() 

This is the minimal fix for stable, I'll send cleanups later.

Commit 854a6ed5 ("signal: Add restore_user_sigmask()") introduced
the visible change which breaks user-space: a signal temporary unblocked
by set_user_sigmask() can be delivered even if the caller returns
success or timeout.

Change restore_user_sigmask() to accept the additional "interrupted"
argument which should be used instead of signal_pending() check, and
update the callers.

Eric said:

: For clarity.  I don't think this is required by posix, or fundamentally to
: remove the races in select.  It is what linux has always done and we have
: applications who care so I agree this fix is needed.
:
: Further in any case where the semantic change that this patch rolls back
: (aka where allowing a signal to be delivered and the select like call to
: complete) would be advantage we can do as well if not better by using
: signalfd.
:
: Michael is there any chance we can get this guarantee of the linux
: implementation of pselect and friends clearly documented.  The guarantee
: that if the system call completes successfully we are guaranteed that no
: signal that is unblocked by using sigmask will be delivered?

Link: http://lkml.kernel.org/r/20190604134117.GA29963@redhat.com


Fixes: 854a6ed5 ("signal: Add restore_user_sigmask()")
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reported-by: default avatarEric Wong <e@80x24.org>
Tested-by: default avatarEric Wong <e@80x24.org>
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarDeepa Dinamani <deepa.kernel@gmail.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: <stable@vger.kernel.org>	[5.0+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 867bfa4a

fs/aio.c

+20 −8
Original line number Diff line number Diff line
@@ -2095,6 +2095,7 @@ SYSCALL_DEFINE6(io_pgetevents, 
	struct __aio_sigset	ksig = { NULL, };

	sigset_t		ksigmask, sigsaved;

	struct timespec64	ts;

	bool interrupted;

	int ret;



	if (timeout && unlikely(get_timespec64(&ts, timeout)))
@@ -2108,8 +2109,10 @@ SYSCALL_DEFINE6(io_pgetevents, 
		return ret;



	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);

	restore_user_sigmask(ksig.sigmask, &sigsaved);

	if (signal_pending(current) && !ret)



	interrupted = signal_pending(current);

	restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);

	if (interrupted && !ret)

		ret = -ERESTARTNOHAND;



	return ret;
@@ -2128,6 +2131,7 @@ SYSCALL_DEFINE6(io_pgetevents_time32, 
	struct __aio_sigset	ksig = { NULL, };

	sigset_t		ksigmask, sigsaved;

	struct timespec64	ts;

	bool interrupted;

	int ret;



	if (timeout && unlikely(get_old_timespec32(&ts, timeout)))
@@ -2142,8 +2146,10 @@ SYSCALL_DEFINE6(io_pgetevents_time32, 
		return ret;



	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);

	restore_user_sigmask(ksig.sigmask, &sigsaved);

	if (signal_pending(current) && !ret)



	interrupted = signal_pending(current);

	restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);

	if (interrupted && !ret)

		ret = -ERESTARTNOHAND;



	return ret;
@@ -2193,6 +2199,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents, 
	struct __compat_aio_sigset ksig = { NULL, };

	sigset_t ksigmask, sigsaved;

	struct timespec64 t;

	bool interrupted;

	int ret;



	if (timeout && get_old_timespec32(&t, timeout))
@@ -2206,8 +2213,10 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents, 
		return ret;



	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);

	restore_user_sigmask(ksig.sigmask, &sigsaved);

	if (signal_pending(current) && !ret)



	interrupted = signal_pending(current);

	restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);

	if (interrupted && !ret)

		ret = -ERESTARTNOHAND;



	return ret;
@@ -2226,6 +2235,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64, 
	struct __compat_aio_sigset ksig = { NULL, };

	sigset_t ksigmask, sigsaved;

	struct timespec64 t;

	bool interrupted;

	int ret;



	if (timeout && get_timespec64(&t, timeout))
@@ -2239,8 +2249,10 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64, 
		return ret;



	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);

	restore_user_sigmask(ksig.sigmask, &sigsaved);

	if (signal_pending(current) && !ret)



	interrupted = signal_pending(current);

	restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);

	if (interrupted && !ret)

		ret = -ERESTARTNOHAND;



	return ret;

fs/eventpoll.c

+2 −2
Original line number Diff line number Diff line
@@ -2325,7 +2325,7 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, 


	error = do_epoll_wait(epfd, events, maxevents, timeout);



	restore_user_sigmask(sigmask, &sigsaved);

	restore_user_sigmask(sigmask, &sigsaved, error == -EINTR);



	return error;

}
@@ -2350,7 +2350,7 @@ COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd, 


	err = do_epoll_wait(epfd, events, maxevents, timeout);



	restore_user_sigmask(sigmask, &sigsaved);

	restore_user_sigmask(sigmask, &sigsaved, err == -EINTR);



	return err;

}

fs/io_uring.c

+4 −3
Original line number Diff line number Diff line
@@ -2201,11 +2201,12 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, 
	}



	ret = wait_event_interruptible(ctx->wait, io_cqring_events(ring) >= min_events);

	if (ret == -ERESTARTSYS)

		ret = -EINTR;



	if (sig)

		restore_user_sigmask(sig, &sigsaved);

		restore_user_sigmask(sig, &sigsaved, ret == -ERESTARTSYS);



	if (ret == -ERESTARTSYS)

		ret = -EINTR;



	return READ_ONCE(ring->r.head) == READ_ONCE(ring->r.tail) ? ret : 0;

}

fs/select.c

+6 −12
Original line number Diff line number Diff line
@@ -758,10 +758,9 @@ static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 
		return ret;



	ret = core_sys_select(n, inp, outp, exp, to);

	restore_user_sigmask(sigmask, &sigsaved, ret == -ERESTARTNOHAND);

	ret = poll_select_copy_remaining(&end_time, tsp, type, ret);



	restore_user_sigmask(sigmask, &sigsaved);



	return ret;

}
@@ -1106,8 +1105,7 @@ SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 


	ret = do_sys_poll(ufds, nfds, to);



	restore_user_sigmask(sigmask, &sigsaved);



	restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);

	/* We can restart this syscall, usually */

	if (ret == -EINTR)

		ret = -ERESTARTNOHAND;
@@ -1142,8 +1140,7 @@ SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, unsigned int, nfds, 


	ret = do_sys_poll(ufds, nfds, to);



	restore_user_sigmask(sigmask, &sigsaved);



	restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);

	/* We can restart this syscall, usually */

	if (ret == -EINTR)

		ret = -ERESTARTNOHAND;
@@ -1350,10 +1347,9 @@ static long do_compat_pselect(int n, compat_ulong_t __user *inp, 
		return ret;



	ret = compat_core_sys_select(n, inp, outp, exp, to);

	restore_user_sigmask(sigmask, &sigsaved, ret == -ERESTARTNOHAND);

	ret = poll_select_copy_remaining(&end_time, tsp, type, ret);



	restore_user_sigmask(sigmask, &sigsaved);



	return ret;

}
@@ -1425,8 +1421,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, 


	ret = do_sys_poll(ufds, nfds, to);



	restore_user_sigmask(sigmask, &sigsaved);



	restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);

	/* We can restart this syscall, usually */

	if (ret == -EINTR)

		ret = -ERESTARTNOHAND;
@@ -1461,8 +1456,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time64, struct pollfd __user *, ufds, 


	ret = do_sys_poll(ufds, nfds, to);



	restore_user_sigmask(sigmask, &sigsaved);



	restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);

	/* We can restart this syscall, usually */

	if (ret == -EINTR)

		ret = -ERESTARTNOHAND;

include/linux/signal.h

+1 −1
Original line number Diff line number Diff line
@@ -276,7 +276,7 @@ extern int sigprocmask(int, sigset_t *, sigset_t *); 
extern int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set,

	sigset_t *oldset, size_t sigsetsize);

extern void restore_user_sigmask(const void __user *usigmask,

				 sigset_t *sigsaved);

				 sigset_t *sigsaved, bool interrupted);

extern void set_current_blocked(sigset_t *);

extern void __set_current_blocked(const sigset_t *);

extern int show_unhandled_signals;

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