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Subject[214/262] [SCSI] st: fix race in st_scsi_execute_end
3.0-stable review patch.  If anyone has any objections, please let me know.


From: Petr Uzel <>

commit c68bf8eeaa57c852e74adcf597237be149eef830 upstream.

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.

Signed-off-by: Petr Uzel <>
Reported-by: Juergen Groß <>
Reviewed-by: Jan Kara <>
Acked-by: Kai Mäkisara <>
Signed-off-by: James Bottomley <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/scsi/st.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -462,14 +462,16 @@ static void st_scsi_execute_end(struct r
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)

- blk_rq_unmap_user(SRpnt->bio);
+ blk_rq_unmap_user(tmp);
__blk_put_request(req->q, req);

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