[patch 106/108] ide-cd: prevent null pointer deref via cdrom_newpc_intr

[Greg KH]

2.6.30-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Rainer Weikusat <rweikusat@xxxxxxxxxxx>

commit 39c58f37a10198054c656c28202fb1e6d22fd505 upstream.

With 2.6.30, the error handling code in cdrom_newpc_intr was changed
to deal with partial request failures by normally completing the 'good'
parts of a request and only 'error' the last (and presumably,
incompletely transferred) bio associated with a particular
request. In order to do this, ide_complete_rq is called over
ide_cd_error_cmd() to partially complete the rq. The block layer
does partial completion only for requests with bio's and if the
rq doesn't have one (eg 'GPCMD_READ_DISC_INFO') the request is
completed as a whole and the drive->hwif->rq pointer set to NULL
afterwards. When calling ide_complete_rq again to report
the error, this null pointer is derefenced, resulting in a kernel
crash.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=13399.

Signed-off-by: Rainer Weikusat <rweikusat@xxxxxxxxxxx>
Signed-off-by: Borislav Petkov <petkovbb@xxxxxxxxx>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/ide/ide-cd.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -758,7 +758,7 @@ out_end:
 				rq->errors = -EIO;
 		}
 
-		if (uptodate == 0)
+		if (uptodate == 0 && rq->bio)
 			ide_cd_error_cmd(drive, cmd);
 
 		/* make sure it's fully ended */


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