From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Tue, 22 Aug 2006 17:22:13 +0000 (+0400)
Subject: elv_unregister: fix possible crash on module unload
X-Git-Tag: v2.6.17.10~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4bf7989b2326fecad1181985f5fa9860d50fb89f;p=thirdparty%2Fkernel%2Fstable.git

elv_unregister: fix possible crash on module unload

An exiting task or process which didn't do I/O yet have no io context,
elv_unregister() should check it is not NULL.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/block/elevator.c b/block/elevator.c
index a0afdd317ceff..7be96bbe142c6 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -766,7 +766,8 @@ void elv_unregister(struct elevator_type *e)
 		read_lock(&tasklist_lock);
 		do_each_thread(g, p) {
 			task_lock(p);
-			e->ops.trim(p->io_context);
+			if (p->io_context)
+				e->ops.trim(p->io_context);
 			task_unlock(p);
 		} while_each_thread(g, p);
 		read_unlock(&tasklist_lock);