applicom: Fix potential Spectre v1 vulnerabilities
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Wed, 9 Jan 2019 22:05:10 +0000 (16:05 -0600)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 22 Jan 2019 12:34:35 +0000 (13:34 +0100)
commitd7ac3c6ef5d8ce14b6381d52eb7adafdd6c8bb3c
tree80f36428f5a486c7256dbbd2f742dd1e4fbea929
parent24d48a61f2666630da130cc2ec2e526eacf229e3
applicom: Fix potential Spectre v1 vulnerabilities

IndexCard is 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/char/applicom.c:418 ac_write() warn: potential spectre issue 'apbs' [r]
drivers/char/applicom.c:728 ac_ioctl() warn: potential spectre issue 'apbs' [r] (local cap)

Fix this by sanitizing IndexCard before using it to index apbs.

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/

Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/char/applicom.c