atm: iphase: Fix Spectre v1 vulnerability
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Wed, 31 Jul 2019 03:21:41 +0000 (22:21 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sun, 11 Aug 2019 10:22:16 +0000 (12:22 +0200)
commitb5641e517bd2a44842472424897352b4ae667075
tree419fbe1657e6b2e3b12ff5ef2b628713e7b28a46
parent22395a3e46d611644fdd7b25c521a040dc2e8b51
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: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/atm/iphase.c