Patch "libata: don't try to pass through NCQ commands to non-NCQ devices" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

libata: don't try to pass through NCQ commands to non-NCQ devices

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
libata-don-t-try-to-pass-through-ncq-commands-to-non-ncq-devices.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Biggers <[email protected]>
Date: Sat, 3 Feb 2018 20:33:51 -0800
Subject: libata: don't try to pass through NCQ commands to non-NCQ devices

From: Eric Biggers <[email protected]>

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));
    }

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

@@ -3226,6 +3226,12 @@ 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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/libata-fix-length-validation-of-atapi-relayed-scsi-commands.patch queue-4.9/libata-remove-warn-for-dma-or-pio-command-without-data.patch queue-4.9/libata-don-t-try-to-pass-through-ncq-commands-to-non-ncq-devices.patch