linux-kernel - [PATCH 3/3] coredump: make wait_for_dump

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130224173209.GA32209@redhat.com>
Date:	Sun, 24 Feb 2013 18:32:09 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mandeep Singh Baines <msb@...omium.org>,
	Neil Horman <nhorman@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] coredump: make wait_for_dump_helpers() freezable

wait_for_dump_helpers() calls wake_up/kill_fasync from inside the
wait_event-like loop. This is not needed and in fact this is not
strictly correct, we can/should do this only once after we change
pipe->writers. We could even check if it becomes zero.

With this change it is trivial to convert this code to use
wait_event_freezable() and make this function freezable/killable,
only SIGKILL can set TIF_SIGPENDING.

With this patch we check pipe->readers without pipe_lock(), this
is fine. Once we see pipe->readers == 1 we know that the handler
decremented the counter, this is all we need.

Note: wait_event_freezable() is "strange", perhaps it should be
changed or simply removed. In the latter case we can change this
code again to use freezer_do_not_count + wait_event_interruptible.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/coredump.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 4f3c8d1..284d841 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -32,6 +32,7 @@
 #include <linux/pipe_fs_i.h>
 #include <linux/oom.h>
 #include <linux/compat.h>
+#include <linux/freezer.h>

 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -428,17 +429,16 @@ static void wait_for_dump_helpers(struct file *file)
 	pipe_lock(pipe);
 	pipe->readers++;
 	pipe->writers--;
+	wake_up_interruptible_sync(&pipe->wait);
+	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+	pipe_unlock(pipe);

-	while ((pipe->readers > 1) && (!signal_pending(current))) {
-		wake_up_interruptible_sync(&pipe->wait);
-		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
-		pipe_wait(pipe);
-	}
+	wait_event_freezable(pipe->wait, pipe->readers == 1);

+	pipe_lock(pipe);
 	pipe->readers--;
 	pipe->writers++;
 	pipe_unlock(pipe);
-
 }

 /*
-- 
1.5.5.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/