Commit f0e3b74a authored Oct 16, 2018 by Gustavo A. R. Silva Committed by Greg Kroah-Hartman Nov 10, 2018

IB/ucm: Fix Spectre v1 vulnerability

commit 0295e395 upstream.

hdr.cmd can be indirectly controlled by user-space, hence leading to
a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

drivers/infiniband/core/ucm.c:1127 ib_ucm_write() warn: potential
spectre issue 'ucm_cmd_table' [r] (local cap)

Fix this by sanitizing hdr.cmd before using it to index
ucm_cmd_table.

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2



Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 66448066

drivers/infiniband/core/ucm.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -46,6 +46,8 @@
		#include <linux/mutex.h>
		#include <linux/slab.h>

		#include <linux/nospec.h>

		#include <linux/uaccess.h>

		#include <rdma/ib.h>
		@@ -1118,6 +1120,7 @@ static ssize_t ib_ucm_write(struct file filp, const char __user buf,

		if (hdr.cmd >= ARRAY_SIZE(ucm_cmd_table))
		return -EINVAL;
		hdr.cmd = array_index_nospec(hdr.cmd, ARRAY_SIZE(ucm_cmd_table));

		if (hdr.in + sizeof(hdr) > len)
		return -EINVAL;