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Commit 128394ef authored Dec 16, 2016 by Al Viro

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



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>

parent f698cccb

block/bsg.c

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -655,6 +655,9 @@ bsg_write(struct file file, const char __user buf, size_t count, loff_t *ppos)

	dprintk("%s: write %Zd bytes\n", bd->name, count);		dprintk("%s: write %Zd bytes\n", bd->name, count);

			if (unlikely(segment_eq(get_fs(), KERNEL_DS)))
			return -EINVAL;

	bsg_set_block(bd, file);		bsg_set_block(bd, file);

	bytes_written = 0;		bytes_written = 0;

drivers/scsi/sg.c

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -581,6 +581,9 @@ sg_write(struct file filp, const char __user buf, size_t count, loff_t * ppos)
	sg_io_hdr_t *hp;		sg_io_hdr_t *hp;
	unsigned char cmnd[SG_MAX_CDB_SIZE];		unsigned char cmnd[SG_MAX_CDB_SIZE];

			if (unlikely(segment_eq(get_fs(), KERNEL_DS)))
			return -EINVAL;

	if ((!(sfp = (Sg_fd *) filp->private_data)) \|\| (!(sdp = sfp->parentdp)))		if ((!(sfp = (Sg_fd *) filp->private_data)) \|\| (!(sdp = sfp->parentdp)))
	return -ENXIO;		return -ENXIO;
	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,		SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,