[PATCH v3 5.10/5.15] ata: libata-scsi: check cdb length for VARIABLE_LENGTH_CMD commands

[Mikhail Ukhin]

No upstream commit exists for this patch.

Fuzzing of 5.10 stable branch reports a slab-out-of-bounds error in
ata_scsi_pass_thru.

The error is fixed in 5.18 by commit ce70fd9a551a ("scsi: core: Remove the
cmd field from struct scsi_request") upstream.
Backporting this commit would require significant changes to the code so
it is bettter to use a simple fix for that particular error.

The problem is that the length of the received SCSI command is not
validated if scsi_op == VARIABLE_LENGTH_CMD. It can lead to out-of-bounds
reading if the user sends a request with SCSI command of length less than
32.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Signed-off-by: Artem Sadovnikov <ancowi69@xxxxxxxxx>
Signed-off-by: Mikhail Ivanov <iwanov-23@xxxxx>
Signed-off-by: Mikhail Ukhin <mish.uxin2012@xxxxxxxxx>
---
 v2: The new addresses were added and the text was updated.
 v3: Checking has been moved to the function ata_scsi_var_len_cdb_xlat at
 the request of Damien Le Moal
 drivers/ata/libata-scsi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index dfa090ccd21c..38488bd813d1 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3948,7 +3948,11 @@ static unsigned int ata_scsi_var_len_cdb_xlat(struct ata_queued_cmd *qc)
 	struct scsi_cmnd *scmd = qc->scsicmd;
 	const u8 *cdb = scmd->cmnd;
 	const u16 sa = get_unaligned_be16(&cdb[8]);
+	u8 scsi_op = scmd->cmnd[0];
 
+	if (scsi_op == VARIABLE_LENGTH_CMD && scmd->cmd_len < 32)
+        	return 1;
+	
 	/*
 	 * if service action represents a ata pass-thru(32) command,
 	 * then pass it to ata_scsi_pass_thru handler.
-- 
2.25.1