linux-kernel - [PATCH] scsi: sd: skip checks when media is present if sd_read

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Message-Id: <20210506073610.33867-1-phil@philpotter.co.uk>
Date:   Thu,  6 May 2021 08:36:10 +0100
From:   Phillip Potter <phil@...lpotter.co.uk>
To:     jejb@...ux.ibm.com
Cc:     martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] scsi: sd: skip checks when media is present if sd_read_capacity reports zero

In sd_revalidate_disk, if sdkp->media_present is set, then sdkp->capacity
should not be zero. Therefore, jump to end of if block and skip remaining
checks/calls. Fixes a KMSAN-found uninit-value bug reported by syzbot at:
https://syzkaller.appspot.com/bug?id=197c8a3a2de61720a9b500ad485a7aba0065c6af

Reported-by: syzbot+6b02c1da3865f750164a@...kaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@...lpotter.co.uk>
---
 drivers/scsi/sd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index ed0b1bb99f08..a7fe53f492ae 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3201,6 +3201,8 @@ static int sd_revalidate_disk(struct gendisk *disk)
 	 */
 	if (sdkp->media_present) {
 		sd_read_capacity(sdkp, buffer);
+		if (!sdkp->capacity)
+			goto present_block_end;
 
 		/*
 		 * set the default to rotational.  All non-rotational devices
@@ -3226,6 +3228,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
 		sd_read_write_same(sdkp, buffer);
 		sd_read_security(sdkp, buffer);
 	}
+present_block_end:
 
 	/*
 	 * We now have all cache related info, determine how we deal
-- 
2.30.2