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Subject[PATCH 4.15 036/105] libata: dont try to pass through NCQ commands to non-NCQ devices
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Biggers <ebiggers@google.com>

commit 2c1ec6fda2d07044cda922ee25337cf5d4b429b3 upstream.

syzkaller hit a WARN() in ata_bmdma_qc_issue() when writing to /dev/sg0.
This happened because it issued an ATA pass-through command (ATA_16)
where the protocol field indicated that NCQ should be used -- but the
device did not support NCQ.

We could just remove the WARN() from libata-sff.c, but the real problem
seems to be that the SCSI -> ATA translation code passes through NCQ
commands without verifying that the device actually supports NCQ.

Fix this by adding the appropriate check to ata_scsi_pass_thru().

Here's reproducer that works in QEMU when /dev/sg0 refers to a disk of
the default type ("82371SB PIIX3 IDE"):

#include <fcntl.h>
#include <unistd.h>

int main()
{
char buf[53] = { 0 };

buf[36] = 0x85; /* ATA_16 */
buf[37] = (12 << 1); /* FPDMA */
buf[38] = 0x1; /* Has data */
buf[51] = 0xC8; /* ATA_CMD_READ */
write(open("/dev/sg0", O_RDWR), buf, sizeof(buf));
}

Fixes: ee7fb331c3ac ("libata: add support for NCQ commands for SG interface")
Reported-by: syzbot+2f69ca28df61bdfc77cd36af2e789850355a221e@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/ata/libata-scsi.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3316,6 +3316,12 @@ static unsigned int ata_scsi_pass_thru(s
goto invalid_fld;
}

+ /* We may not issue NCQ commands to devices not supporting NCQ */
+ if (ata_is_ncq(tf->protocol) && !ata_ncq_enabled(dev)) {
+ fp = 1;
+ goto invalid_fld;
+ }
+
/* sanity check for pio multi commands */
if ((cdb[1] & 0xe0) && !is_multi_taskfile(tf)) {
fp = 1;

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