sg_write()/bsg_write() is not fit to be called under KERNEL_DS

commit a0ac402cfcdc904f9772e1762b3fda112dcc56a0 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.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/block/bsg.c b/block/bsg.c
index c0ab25c..2a01940 100644 (file)
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -675,6 +675,9 @@ 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 94b71b4..fb59a49 100644 (file)
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -544,6 +544,9 @@ 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",