The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2c1ec6fda2d07044cda922ee25337cf5d4b429b3 Mon Sep 17 00:00:00 2001

From: Eric Biggers ebiggers@google.com Date: Sat, 3 Feb 2018 20:33:51 -0800 Subject: [PATCH] libata: don't try to pass through NCQ commands to non-NCQ devices

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

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 9ae8986bae48..89a9d4a2efc8 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -3316,6 +3316,12 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc) 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;