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[SCSI] st: fix race in st_scsi_execute_end 

The call to complete() in st_scsi_execute_end() wakes up sleeping thread
in write_behind_check(), which frees the st_request, thus invalidating
the pointer to the associated bio structure, which is then passed to the
blk_rq_unmap_user(). Fix by storing pointer to bio structure into
temporary local variable.

This bug is present since at least linux-2.6.32.

CC: stable@kernel.org
Signed-off-by: Petr Uzel <petr.uzel@suse.cz>
Reported-by: Juergen Groß <juergen.gross@ts.fujitsu.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Petr Uzel 2011-10-21 13:31:09 +02:00 committed by James Bottomley
parent 3308511c93
commit c68bf8eeaa
1 changed files with 3 additions and 1 deletions
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4
drivers/scsi/st.c
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@ -462,14 +462,16 @@ static void st_scsi_execute_end(struct request *req, int uptodate)
{
struct st_request *SRpnt = req->end_io_data;
struct scsi_tape *STp = SRpnt->stp;
struct bio *tmp;
STp->buffer->cmdstat.midlevel_result = SRpnt->result = req->errors;
STp->buffer->cmdstat.residual = req->resid_len;
tmp = SRpnt->bio;
if (SRpnt->waiting)
complete(SRpnt->waiting);
blk_rq_unmap_user(SRpnt->bio);
blk_rq_unmap_user(tmp);
__blk_put_request(req->q, req);
}