From 97abc889ee296faf95ca0e978340fb7b942a3e32 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 28 Jun 2019 12:06:50 -0700 Subject: signal: remove the wrong signal_pending() check in restore_user_sigmask() 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 Reported-by: Eric Wong Tested-by: Eric Wong Acked-by: "Eric W. Biederman" Acked-by: Arnd Bergmann Acked-by: Deepa Dinamani Cc: Michael Kerrisk Cc: Jens Axboe Cc: Davidlohr Bueso Cc: Jason Baron Cc: Thomas Gleixner Cc: Al Viro Cc: David Laight Cc: [5.0+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/aio.c | 28 ++++++++++++++++++++-------- fs/eventpoll.c | 4 ++-- fs/io_uring.c | 7 ++++--- fs/select.c | 18 ++++++------------ 4 files changed, 32 insertions(+), 25 deletions(-) (limited to 'fs') diff --git a/fs/aio.c b/fs/aio.c index 3490d1fa0e16..c1e581dd32f5 100644 --- 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 c6f513100cc9..4c74c768ae43 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -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; } diff --git a/fs/io_uring.c b/fs/io_uring.c index 86a2bd721900..e6981d3f4468 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -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; } diff --git a/fs/select.c b/fs/select.c index 6cbc9ff56ba0..a4d8f6e8b63c 100644 --- 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; -- cgit