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Commit eee434d2 authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Greg Kroah-Hartman
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atm: iphase: Fix Spectre v1 vulnerability 

[ Upstream commit ea443e5e98b5b74e317ef3d26bcaea54931ccdee ]

board is 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/atm/iphase.c:2765 ia_ioctl() warn: potential spectre issue 'ia_dev' [r] (local cap)
drivers/atm/iphase.c:2774 ia_ioctl() warn: possible spectre second half.  'iadev'
drivers/atm/iphase.c:2782 ia_ioctl() warn: possible spectre second half.  'iadev'
drivers/atm/iphase.c:2816 ia_ioctl() warn: possible spectre second half.  'iadev'
drivers/atm/iphase.c:2823 ia_ioctl() warn: possible spectre second half.  'iadev'
drivers/atm/iphase.c:2830 ia_ioctl() warn: potential spectre issue '_ia_dev' [r] (local cap)
drivers/atm/iphase.c:2845 ia_ioctl() warn: possible spectre second half.  'iadev'
drivers/atm/iphase.c:2856 ia_ioctl() warn: possible spectre second half.  'iadev'

Fix this by sanitizing board before using it to index ia_dev and _ia_dev

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://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/



Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5917ca48

drivers/atm/iphase.c

+6 −2
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ 
#include <asm/byteorder.h>  

#include <linux/vmalloc.h>

#include <linux/jiffies.h>

#include <linux/nospec.h>

#include "iphase.h"		  

#include "suni.h"		  

#define swap_byte_order(x) (((x & 0xff) << 8) | ((x & 0xff00) >> 8))
@@ -2755,8 +2756,11 @@ static int ia_ioctl(struct atm_dev *dev, unsigned int cmd, void __user *arg) 
   }

   if (copy_from_user(&ia_cmds, arg, sizeof ia_cmds)) return -EFAULT; 

   board = ia_cmds.status;



	if ((board < 0) || (board > iadev_count))

		board = 0;

	board = array_index_nospec(board, iadev_count + 1);



   iadev = ia_dev[board];

   switch (ia_cmds.cmd) {

   case MEMDUMP: