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oleg-nesterovtorvalds
oleg-nesterov
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signal: remove the wrong signal_pending() check in restore_user_sigmask()
This is the minimal fix for stable, I'll send cleanups later. Commit 854a6ed ("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/[email protected] Fixes: 854a6ed ("signal: Add restore_user_sigmask()") Signed-off-by: Oleg Nesterov <[email protected]> Reported-by: Eric Wong <[email protected]> Tested-by: Eric Wong <[email protected]> Acked-by: "Eric W. Biederman" <[email protected]> Acked-by: Arnd Bergmann <[email protected]> Acked-by: Deepa Dinamani <[email protected]> Cc: Michael Kerrisk <[email protected]> Cc: Jens Axboe <[email protected]> Cc: Davidlohr Bueso <[email protected]> Cc: Jason Baron <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Al Viro <[email protected]> Cc: David Laight <[email protected]> Cc: <[email protected]> [5.0+] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
1 parent 867bfa4 commit 97abc88

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6 files changed

+36
-28
lines changed

6 files changed

+36
-28
lines changed

‎fs/aio.c

Lines changed: 20 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -2095,6 +2095,7 @@ SYSCALL_DEFINE6(io_pgetevents,
20952095
struct __aio_sigset ksig = { NULL, };
20962096
sigset_t ksigmask, sigsaved;
20972097
struct timespec64 ts;
2098+
bool interrupted;
20982099
int ret;
20992100

21002101
if (timeout && unlikely(get_timespec64(&ts, timeout)))
@@ -2108,8 +2109,10 @@ SYSCALL_DEFINE6(io_pgetevents,
21082109
return ret;
21092110

21102111
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
2111-
restore_user_sigmask(ksig.sigmask, &sigsaved);
2112-
if (signal_pending(current) && !ret)
2112+
2113+
interrupted = signal_pending(current);
2114+
restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
2115+
if (interrupted && !ret)
21132116
ret = -ERESTARTNOHAND;
21142117

21152118
return ret;
@@ -2128,6 +2131,7 @@ SYSCALL_DEFINE6(io_pgetevents_time32,
21282131
struct __aio_sigset ksig = { NULL, };
21292132
sigset_t ksigmask, sigsaved;
21302133
struct timespec64 ts;
2134+
bool interrupted;
21312135
int ret;
21322136

21332137
if (timeout && unlikely(get_old_timespec32(&ts, timeout)))
@@ -2142,8 +2146,10 @@ SYSCALL_DEFINE6(io_pgetevents_time32,
21422146
return ret;
21432147

21442148
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
2145-
restore_user_sigmask(ksig.sigmask, &sigsaved);
2146-
if (signal_pending(current) && !ret)
2149+
2150+
interrupted = signal_pending(current);
2151+
restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
2152+
if (interrupted && !ret)
21472153
ret = -ERESTARTNOHAND;
21482154

21492155
return ret;
@@ -2193,6 +2199,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
21932199
struct __compat_aio_sigset ksig = { NULL, };
21942200
sigset_t ksigmask, sigsaved;
21952201
struct timespec64 t;
2202+
bool interrupted;
21962203
int ret;
21972204

21982205
if (timeout && get_old_timespec32(&t, timeout))
@@ -2206,8 +2213,10 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
22062213
return ret;
22072214

22082215
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
2209-
restore_user_sigmask(ksig.sigmask, &sigsaved);
2210-
if (signal_pending(current) && !ret)
2216+
2217+
interrupted = signal_pending(current);
2218+
restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
2219+
if (interrupted && !ret)
22112220
ret = -ERESTARTNOHAND;
22122221

22132222
return ret;
@@ -2226,6 +2235,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
22262235
struct __compat_aio_sigset ksig = { NULL, };
22272236
sigset_t ksigmask, sigsaved;
22282237
struct timespec64 t;
2238+
bool interrupted;
22292239
int ret;
22302240

22312241
if (timeout && get_timespec64(&t, timeout))
@@ -2239,8 +2249,10 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
22392249
return ret;
22402250

22412251
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
2242-
restore_user_sigmask(ksig.sigmask, &sigsaved);
2243-
if (signal_pending(current) && !ret)
2252+
2253+
interrupted = signal_pending(current);
2254+
restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
2255+
if (interrupted && !ret)
22442256
ret = -ERESTARTNOHAND;
22452257

22462258
return ret;

‎fs/eventpoll.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2325,7 +2325,7 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
23252325

23262326
error = do_epoll_wait(epfd, events, maxevents, timeout);
23272327

2328-
restore_user_sigmask(sigmask, &sigsaved);
2328+
restore_user_sigmask(sigmask, &sigsaved, error == -EINTR);
23292329

23302330
return error;
23312331
}
@@ -2350,7 +2350,7 @@ COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
23502350

23512351
err = do_epoll_wait(epfd, events, maxevents, timeout);
23522352

2353-
restore_user_sigmask(sigmask, &sigsaved);
2353+
restore_user_sigmask(sigmask, &sigsaved, err == -EINTR);
23542354

23552355
return err;
23562356
}

‎fs/io_uring.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2201,11 +2201,12 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
22012201
}
22022202

22032203
ret = wait_event_interruptible(ctx->wait, io_cqring_events(ring) >= min_events);
2204-
if (ret == -ERESTARTSYS)
2205-
ret = -EINTR;
22062204

22072205
if (sig)
2208-
restore_user_sigmask(sig, &sigsaved);
2206+
restore_user_sigmask(sig, &sigsaved, ret == -ERESTARTSYS);
2207+
2208+
if (ret == -ERESTARTSYS)
2209+
ret = -EINTR;
22092210

22102211
return READ_ONCE(ring->r.head) == READ_ONCE(ring->r.tail) ? ret : 0;
22112212
}

‎fs/select.c

Lines changed: 6 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -758,10 +758,9 @@ static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
758758
return ret;
759759

760760
ret = core_sys_select(n, inp, outp, exp, to);
761+
restore_user_sigmask(sigmask, &sigsaved, ret == -ERESTARTNOHAND);
761762
ret = poll_select_copy_remaining(&end_time, tsp, type, ret);
762763

763-
restore_user_sigmask(sigmask, &sigsaved);
764-
765764
return ret;
766765
}
767766

@@ -1106,8 +1105,7 @@ SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
11061105

11071106
ret = do_sys_poll(ufds, nfds, to);
11081107

1109-
restore_user_sigmask(sigmask, &sigsaved);
1110-
1108+
restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
11111109
/* We can restart this syscall, usually */
11121110
if (ret == -EINTR)
11131111
ret = -ERESTARTNOHAND;
@@ -1142,8 +1140,7 @@ SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, unsigned int, nfds,
11421140

11431141
ret = do_sys_poll(ufds, nfds, to);
11441142

1145-
restore_user_sigmask(sigmask, &sigsaved);
1146-
1143+
restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
11471144
/* We can restart this syscall, usually */
11481145
if (ret == -EINTR)
11491146
ret = -ERESTARTNOHAND;
@@ -1350,10 +1347,9 @@ static long do_compat_pselect(int n, compat_ulong_t __user *inp,
13501347
return ret;
13511348

13521349
ret = compat_core_sys_select(n, inp, outp, exp, to);
1350+
restore_user_sigmask(sigmask, &sigsaved, ret == -ERESTARTNOHAND);
13531351
ret = poll_select_copy_remaining(&end_time, tsp, type, ret);
13541352

1355-
restore_user_sigmask(sigmask, &sigsaved);
1356-
13571353
return ret;
13581354
}
13591355

@@ -1425,8 +1421,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds,
14251421

14261422
ret = do_sys_poll(ufds, nfds, to);
14271423

1428-
restore_user_sigmask(sigmask, &sigsaved);
1429-
1424+
restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
14301425
/* We can restart this syscall, usually */
14311426
if (ret == -EINTR)
14321427
ret = -ERESTARTNOHAND;
@@ -1461,8 +1456,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time64, struct pollfd __user *, ufds,
14611456

14621457
ret = do_sys_poll(ufds, nfds, to);
14631458

1464-
restore_user_sigmask(sigmask, &sigsaved);
1465-
1459+
restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
14661460
/* We can restart this syscall, usually */
14671461
if (ret == -EINTR)
14681462
ret = -ERESTARTNOHAND;

‎include/linux/signal.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -276,7 +276,7 @@ extern int sigprocmask(int, sigset_t *, sigset_t *);
276276
extern int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set,
277277
sigset_t *oldset, size_t sigsetsize);
278278
extern void restore_user_sigmask(const void __user *usigmask,
279-
sigset_t *sigsaved);
279+
sigset_t *sigsaved, bool interrupted);
280280
extern void set_current_blocked(sigset_t *);
281281
extern void __set_current_blocked(const sigset_t *);
282282
extern int show_unhandled_signals;

‎kernel/signal.c

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2912,7 +2912,8 @@ EXPORT_SYMBOL(set_compat_user_sigmask);
29122912
* This is useful for syscalls such as ppoll, pselect, io_pgetevents and
29132913
* epoll_pwait where a new sigmask is passed in from userland for the syscalls.
29142914
*/
2915-
void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved)
2915+
void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved,
2916+
bool interrupted)
29162917
{
29172918

29182919
if (!usigmask)
@@ -2922,7 +2923,7 @@ void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved)
29222923
* Restoring sigmask here can lead to delivering signals that the above
29232924
* syscalls are intended to block because of the sigmask passed in.
29242925
*/
2925-
if (signal_pending(current)) {
2926+
if (interrupted) {
29262927
current->saved_sigmask = *sigsaved;
29272928
set_restore_sigmask();
29282929
return;

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