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.gy17...@dhcp22.suse.cz/ Cc: sta...@vger.kernel.org Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com> --- drivers/atm/iphase.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/atm/iphase.c b/drivers/atm/iphase.c index 302cf0ba1600..8c7a996d1f16 100644 --- a/drivers/atm/iphase.c +++ b/drivers/atm/iphase.c @@ -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)) @@ -2760,8 +2761,11 @@ 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; + + 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: -- 2.22.0
