linux-kernel - [PATCH 2/2] aio: fix the usage of restore_saved_sigmask

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Date:   Fri, 7 Jun 2019 12:32:23 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Benjamin LaHaise <bcrl@...ck.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        David Laight <David.Laight@...LAB.COM>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Eric Wong <e@...24.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-aio@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] aio: fix the usage of restore_saved_sigmask_unless()

do_io_getevents() is the only user of set/restore_user_sigmask which
can return success or error and deliver a signal which was temporary
unblocked by set_user_sigmask().

Change it to keep the modified sigmask (pass true to restore_unless)
only if the syscall returns ERESTARTNOHAND/EINTR. This matches all
other syscalls which modify current->blocked before wait-for-event.

Note that it doesn't even need the signal_pending() check, read_event()
wait_event_interruptible_hrtimeout() returns ERESTARTSYS if interrupted.
But it seems that read_events() needs some unrelated cleanups which
should be done first.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/aio.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 944eef7..5bdbef0 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -2034,7 +2034,6 @@ static long do_io_getevents(aio_context_t ctx_id,
 {
 	ktime_t until = ts ? timespec64_to_ktime(*ts) : KTIME_MAX;
 	struct kioctx *ioctx = lookup_ioctx(ctx_id);
-	bool interrupted;
 	long ret = -EINVAL;
 
 	if (likely(ioctx)) {
@@ -2043,10 +2042,9 @@ static long do_io_getevents(aio_context_t ctx_id,
 		percpu_ref_put(&ioctx->users);
 	}
 
-	interrupted = signal_pending(current);
-	restore_saved_sigmask_unless(interrupted);
-	if (interrupted && !ret)
+	if (!ret && signal_pending(current))
 		ret = -ERESTARTNOHAND;
+	restore_saved_sigmask_unless(ret == -ERESTARTNOHAND);
 
 	return ret;
 }
-- 
2.5.0