From: Al Viro Date: Fri, 16 Dec 2016 18:42:06 +0000 (-0500) Subject: sg_write()/bsg_write() is not fit to be called under KERNEL_DS X-Git-Tag: v3.16.40~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=249741c2c0d7a905da66efc6d1292d3915aef1fc;p=thirdparty%2Fkernel%2Fstable.git sg_write()/bsg_write() is not fit to be called under KERNEL_DS commit 128394eff343fc6d2f32172f03e24829539c5835 upstream. Both damn things interpret userland pointers embedded into the payload; worse, they are actually traversing those. Leaving aside the bad API design, this is very much _not_ safe to call with KERNEL_DS. Bail out early if that happens. Signed-off-by: Al Viro Signed-off-by: Ben Hutchings --- diff --git a/block/bsg.c b/block/bsg.c index ff46addde5d8e..8af4880ab2a2f 100644 --- a/block/bsg.c +++ b/block/bsg.c @@ -676,6 +676,9 @@ bsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) dprintk("%s: write %Zd bytes\n", bd->name, count); + if (unlikely(segment_eq(get_fs(), KERNEL_DS))) + return -EINVAL; + bsg_set_block(bd, file); bytes_written = 0; diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 30973aeec2f49..b4d50662fc6f4 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -568,6 +568,9 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos) sg_io_hdr_t *hp; unsigned char cmnd[MAX_COMMAND_SIZE]; + if (unlikely(segment_eq(get_fs(), KERNEL_DS))) + return -EINVAL; + if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp))) return -ENXIO; SCSI_LOG_TIMEOUT(3, printk("sg_write: %s, count=%d\n",