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

commit 97abc889ee296faf95ca0e978340fb7b942a3e32 upstream.

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

Commit 854a6ed56839 ("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: 854a6ed56839a40f6b5d02a2962f48841482eec4 ("signal: Add restore_user_sigmask()")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Eric Wong <e@80x24.org>
Tested-by: Eric Wong <e@80x24.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Deepa 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/aio.c b/fs/aio.c
index 3490d1fa0e16f4f1f189727661e18696ab3a7a08..c1e581dd32f52b3636e900389ffe1876a0ff4dd1 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -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;

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 4a0e98d87fcca90fcd06deb5d64ac6dd1f0f2ed9..55c0e1c75ad1b213f62fafc2677dc72023dc94d2 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2330,7 +2330,7 @@ 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;
 }
@@ -2355,7 +2355,7 @@ 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;
 }

diff --git a/fs/io_uring.c b/fs/io_uring.c
index b897695c91c02517766f439e5cea00b74705ef1a..7d8e8345827826165d1fff692c418712637c6b54 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2096,7 +2096,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
        finish_wait(&ctx->wait, &wait);
 
        if (sig)
-               restore_user_sigmask(sig, &sigsaved);
+               restore_user_sigmask(sig, &sigsaved, ret == -EINTR);
 
        return READ_ONCE(ring->r.head) == READ_ONCE(ring->r.tail) ? ret : 0;
 }

diff --git a/fs/select.c b/fs/select.c
index 6cbc9ff56ba07f004a7c8692caf6eafe7c99b87f..a4d8f6e8b63c82294b896d2979513bbf2f9e5595 100644 (file)
--- a/fs/select.c
+++ b/fs/select.c
@@ -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;

diff --git a/include/linux/signal.h b/include/linux/signal.h
index 9702016734b1ad7e53b204511b1167e05bc6b858..78c2bb37695469d22b0f14e296623ae2888d56fe 100644 (file)
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -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;

diff --git a/kernel/signal.c b/kernel/signal.c
index 429f5663edd9fa368eadc331b238b1b6ab677816..5f3dd69b50e23d5bad8ee7f7e37a541cd0bcbfb6 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2851,7 +2851,8 @@ EXPORT_SYMBOL(set_compat_user_sigmask);
  * This is useful for syscalls such as ppoll, pselect, io_pgetevents and
  * epoll_pwait where a new sigmask is passed in from userland for the syscalls.
  */
-void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved)
+void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved,
+                               bool interrupted)
 {
 
        if (!usigmask)
@@ -2861,7 +2862,7 @@ void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved)
         * Restoring sigmask here can lead to delivering signals that the above
         * syscalls are intended to block because of the sigmask passed in.
         */
-       if (signal_pending(current)) {
+       if (interrupted) {
                current->saved_sigmask = *sigsaved;
                set_restore_sigmask();
                return;