From: Tejun Heo <htejun@gmail.com>
Date: Tue, 1 Nov 2005 08:23:49 +0000 (+0900)
Subject: [PATCH] blk: fix dangling pointer access in __elv_add_request
X-Git-Tag: v2.6.15-rc1~18^2~11
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ca23509fbaac0ea662ab0e287bebb72f743f9e1f;p=pandora-kernel.git

[PATCH] blk: fix dangling pointer access in __elv_add_request

cfq's add_req_fn callback may invoke q->request_fn directly and
depending on low-level driver used and timing, a queued request may be
finished & deallocated before add_req_fn callback returns.  So,
__elv_add_request must not access rq after it's passed to add_req_fn
callback.

This patch moves rq_mergeable test above add_req_fn().  This may
result in q->last_merge pointing to REQ_NOMERGE request if add_req_fn
callback sets it but as RQ_NOMERGE is checked again when blk layer
actually tries to merge requests, this does not cause any problem.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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