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| author | Tejun Heo <htejun@gmail.com> | 2005-11-01 08:23:49 (GMT) |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-02 05:58:06 (GMT) |
| commit | ca23509fbaac0ea662ab0e287bebb72f743f9e1f (patch) | |
| tree | b87f06d928e0ea06ae6244c1aeecf3e745f39bb9 | |
| parent | 6c2af71f7f6ac10ab45e9461e1dd7aa09079643a (diff) | |
| download | linux-ca23509fbaac0ea662ab0e287bebb72f743f9e1f.tar.xz | |
[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>
| -rw-r--r-- | drivers/block/elevator.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c index 36f1057..d4a49a3 100644 --- a/drivers/block/elevator.c +++ b/drivers/block/elevator.c @@ -369,9 +369,14 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where, case ELEVATOR_INSERT_SORT: BUG_ON(!blk_fs_request(rq)); rq->flags |= REQ_SORTED; - q->elevator->ops->elevator_add_req_fn(q, rq); if (q->last_merge == NULL && rq_mergeable(rq)) q->last_merge = rq; + /* + * Some ioscheds (cfq) run q->request_fn directly, so + * rq cannot be accessed after calling + * elevator_add_req_fn. + */ + q->elevator->ops->elevator_add_req_fn(q, rq); break; default: |