From: Zachary Amsden <zach@vmware.com>
Date: Wed, 9 Nov 2005 12:23:01 +0000 (+0100)
Subject: [BLOCK] elevator init fixes
X-Git-Tag: v2.6.16.28-rc1~2746
X-Git-Url: https://git.kernelconcepts.de/?p=karo-tx-linux.git;a=commitdiff_plain;h=b8ea2cb5120a92fe63053a2896be42abbb919a76

[BLOCK] elevator init fixes

I got a panic in the elevator code, backtrace :

Unable to handle kernel NULL pointer dereference at virtual address 00000060
..
EIP is at elevator_put+0x0/0x30 (null elevator_type passed)
..
elevator_init+0x38
blk_init_queu_node+0xc9
floppy_init+0xdb
do_initcalls+0x23
init+0x10a
init+0x0

Clearly if the kmalloc here fails, e->elevator_type is not yet set; this
appears to be the correct fix, but I think I probably hit the second case
due to a race condition.  Someone more familiar with the elevator code
should look at this more closely until I can determine if I can reproduce.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Jens Axboe <axboe@suse.de>
---

diff --git a/block/elevator.c b/block/elevator.c
index d4a49a3df829..23cfbe528be1 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -190,14 +190,14 @@ int elevator_init(request_queue_t *q, char *name)
 
 	eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
 	if (!eq) {
-		elevator_put(e->elevator_type);
+		elevator_put(e);
 		return -ENOMEM;
 	}
 
 	ret = elevator_attach(q, e, eq);
 	if (ret) {
 		kfree(eq);
-		elevator_put(e->elevator_type);
+		elevator_put(e);
 	}
 
 	return ret;