From: Jens Axboe axboe@kernel.dk

commit f7068114d45ec55996b9040e98111afa56e010fe upstream.

We're casting the CDROM layer request_sense to the SCSI sense buffer, but the former is 64 bytes and the latter is 96 bytes. As we generally allocate these on the stack, we end up blowing up the stack.

Fix this by wrapping the scsi_execute() call with a properly sized sense buffer, and copying back the bits for the CDROM layer.

Reported-by: Piotr Gabriel Kosinski pg.kosinski@gmail.com Reported-by: Daniel Shapira daniel@twistlock.com Tested-by: Kees Cook keescook@chromium.org Fixes: 82ed4db499b8 ("block: split scsi_request out of struct request") Signed-off-by: Jens Axboe axboe@kernel.dk [bwh: Despite what the "Fixes" field says, a buffer overrun was already possible if the sense data was really > 64 bytes long. Backported to 4.9: - We always need to allocate a sense buffer in order to call scsi_normalize_sense() - Remove the existing conditional heap-allocation of the sense buffer] Signed-off-by: Ben Hutchings ben.hutchings@codethink.co.uk --- drivers/scsi/sr_ioctl.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/scsi/sr_ioctl.c b/drivers/scsi/sr_ioctl.c index 03054c0e7689..3c3e8115f73d 100644 --- a/drivers/scsi/sr_ioctl.c +++ b/drivers/scsi/sr_ioctl.c @@ -187,30 +187,25 @@ int sr_do_ioctl(Scsi_CD *cd, struct packet_command *cgc) struct scsi_device *SDev; struct scsi_sense_hdr sshdr; int result, err = 0, retries = 0; - struct request_sense *sense = cgc->sense; + unsigned char sense_buffer[SCSI_SENSE_BUFFERSIZE];

SDev = cd->device;

- if (!sense) { - sense = kmalloc(SCSI_SENSE_BUFFERSIZE, GFP_KERNEL); - if (!sense) { - err = -ENOMEM; - goto out; - } - } - retry: if (!scsi_block_when_processing_errors(SDev)) { err = -ENODEV; goto out; }

- memset(sense, 0, sizeof(*sense)); + memset(sense_buffer, 0, sizeof(sense_buffer)); result = scsi_execute(SDev, cgc->cmd, cgc->data_direction, - cgc->buffer, cgc->buflen, (char *)sense, + cgc->buffer, cgc->buflen, sense_buffer, cgc->timeout, IOCTL_RETRIES, 0, NULL);

- scsi_normalize_sense((char *)sense, sizeof(*sense), &sshdr); + scsi_normalize_sense(sense_buffer, sizeof(sense_buffer), &sshdr); + + if (cgc->sense) + memcpy(cgc->sense, sense_buffer, sizeof(*cgc->sense));

/* Minimal error checking. Ignore cases we know about, and report the rest. */ if (driver_byte(result) != 0) { @@ -261,8 +256,6 @@ int sr_do_ioctl(Scsi_CD *cd, struct packet_command *cgc)

/* Wake up a process waiting for device */ out: - if (!cgc->sense) - kfree(sense); cgc->stat = err; return err; }