The patch titled Subject: signal: remove the wrong signal_pending() check in restore_user_sigmask() has been added to the -mm tree. Its filename is signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask.patch
This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/signal-remove-the-wrong-signal_pend... and later at http://ozlabs.org/~akpm/mmotm/broken-out/signal-remove-the-wrong-signal_pend...
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------------------------------------------------------ From: Oleg Nesterov oleg@redhat.com Subject: signal: remove the wrong signal_pending() check in restore_user_sigmask()
This is the minimal fix for stable, I'll send cleanups later.
854a6ed56839a40f6b5 ("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 ---
fs/aio.c | 28 ++++++++++++++++++++-------- fs/eventpoll.c | 4 ++-- fs/io_uring.c | 7 ++++--- fs/select.c | 18 ++++++------------ include/linux/signal.h | 2 +- kernel/signal.c | 5 +++-- 6 files changed, 36 insertions(+), 28 deletions(-)
--- a/fs/aio.c~signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask +++ a/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_tim 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_tim 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; --- a/fs/eventpoll.c~signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask +++ a/fs/eventpoll.c @@ -2325,7 +2325,7 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd,
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,
err = do_epoll_wait(epfd, events, maxevents, timeout);
- restore_user_sigmask(sigmask, &sigsaved); + restore_user_sigmask(sigmask, &sigsaved, err == -EINTR);
return err; } --- a/fs/io_uring.c~signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask +++ a/fs/io_uring.c @@ -2201,11 +2201,12 @@ static int io_cqring_wait(struct io_ring }
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; } --- a/fs/select.c~signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask +++ a/fs/select.c @@ -758,10 +758,9 @@ static long do_pselect(int n, fd_set __u 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 __u
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 pol
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, com 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, str
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, str
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; --- a/include/linux/signal.h~signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask +++ a/include/linux/signal.h @@ -276,7 +276,7 @@ extern int sigprocmask(int, 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; --- a/kernel/signal.c~signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask +++ a/kernel/signal.c @@ -2912,7 +2912,8 @@ 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) @@ -2922,7 +2923,7 @@ void restore_user_sigmask(const void __u * 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; _
Patches currently in -mm which might be from oleg@redhat.com are
signal-remove-the-wrong-signal_pending-check-in-restore_user_sigmask.patch