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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jiri Slaby <jslaby@suse.cz>,
        Jens Axboe <axboe@kernel.dk>, linux-ide@vger.kernel.org,
        Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Subject: [PATCH 4.9 121/121] ata: sata_mv, avoid trigerrable BUG_ON
Date:   Tue, 29 Sep 2020 13:01:05 +0200
Message-Id: <20200929105936.175135632@linuxfoundation.org>
In-Reply-To: <20200929105930.172747117@linuxfoundation.org>
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From: Jiri Slaby <jslaby@suse.cz>

commit e9f691d899188679746eeb96e6cb520459eda9b4 upstream.

There are several reports that the BUG_ON on unsupported command in
mv_qc_prep can be triggered under some circumstances:
https://bugzilla.suse.com/show_bug.cgi?id=1110252
https://serverfault.com/questions/888897/raid-problems-after-power-outage
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1652185
https://bugs.centos.org/view.php?id=14998

Let sata_mv handle the failure gracefully: warn about that incl. the
failed command number and return an AC_ERR_INVALID error. We can do that
now thanks to the previous patch.

Remove also the long-standing FIXME.

[v2] use %.2x as commands are defined as hexa.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-ide@vger.kernel.org
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/ata/sata_mv.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -2111,12 +2111,10 @@ static enum ata_completion_errors mv_qc_
 		 * non-NCQ mode are: [RW] STREAM DMA and W DMA FUA EXT, none
 		 * of which are defined/used by Linux.  If we get here, this
 		 * driver needs work.
-		 *
-		 * FIXME: modify libata to give qc_prep a return value and
-		 * return error here.
 		 */
-		BUG_ON(tf->command);
-		break;
+		ata_port_err(ap, "%s: unsupported command: %.2x\n", __func__,
+				tf->command);
+		return AC_ERR_INVALID;
 	}
 	mv_crqb_pack_cmd(cw++, tf->nsect, ATA_REG_NSECT, 0);
 	mv_crqb_pack_cmd(cw++, tf->hob_lbal, ATA_REG_LBAL, 0);