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

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

[Mikhail Ukhin]

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").
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@gmail.com>
Signed-off-by: Mikhail Ivanov <iwanov-23@bk.ru>
---
 drivers/ata/libata-scsi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index dfa090ccd21c..77589e911d3d 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -4065,6 +4065,9 @@ int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
 
 	if (unlikely(!scmd->cmd_len))
 		goto bad_cdb_len;
+
+	if (scsi_op == VARIABLE_LENGTH_CMD && scmd->cmd_len < 32)
+		goto bad_cdb_len;
 
 	if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
 		if (unlikely(scmd->cmd_len > dev->cdb_len))
-- 
2.25.1

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

[Damien Le Moal]

On 3/29/24 00:00, Mikhail Ukhin wrote:
> 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").
> 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@gmail.com>
> Signed-off-by: Mikhail Ivanov <iwanov-23@bk.ru>

This looks OK to me, but:
1) Please stop using the wrong email address for me. Use
scripts/get_maintainer.pl to see the correct email address (the one I am using
now). And maintainers & main list should not be on cc but part of the "to:"
addressing.
2) Please read Documentation/process/stable-kernel-rules.rst and see Option 3. I
cannot take this patch. It needs to go through the stable tree after I Ack it.

> ---
>  drivers/ata/libata-scsi.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index dfa090ccd21c..77589e911d3d 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -4065,6 +4065,9 @@ int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
>  
>  	if (unlikely(!scmd->cmd_len))
>  		goto bad_cdb_len;
> +
> +	if (scsi_op == VARIABLE_LENGTH_CMD && scmd->cmd_len < 32)
> +		goto bad_cdb_len;
>  
>  	if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
>  		if (unlikely(scmd->cmd_len > dev->cdb_len))

-- 
Damien Le Moal
Western Digital Research