ioc_data.dev_num can be 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: net/atm/lec.c:702 lec_vcc_attach() warn: potential spectre issue 'dev_lec' Fix this by sanitizing ioc_data.dev_num before using it to index dev_lec. Also, notice that there is another instance in which array dev_lec is being indexed using ioc_data.dev_num at line 705: lec_vcc_added(netdev_priv(dev_lec[ioc_data.dev_num]), 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: sta...@vger.kernel.org Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com> --- net/atm/lec.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/atm/lec.c b/net/atm/lec.c index 01d5d20..3138a86 100644 --- a/net/atm/lec.c +++ b/net/atm/lec.c @@ -41,6 +41,9 @@ static unsigned char bridge_ula_lec[] = { 0x01, 0x80, 0xc2, 0x00, 0x00 }; #include <linux/module.h> #include <linux/init.h> +/* Hardening for Spectre-v1 */ +#include <linux/nospec.h> + #include "lec.h" #include "lec_arpc.h" #include "resources.h" @@ -687,8 +690,10 @@ static int lec_vcc_attach(struct atm_vcc *vcc, void __user *arg) bytes_left = copy_from_user(&ioc_data, arg, sizeof(struct atmlec_ioc)); if (bytes_left != 0) pr_info("copy from user failed for %d bytes\n", bytes_left); - if (ioc_data.dev_num < 0 || ioc_data.dev_num >= MAX_LEC_ITF || - !dev_lec[ioc_data.dev_num]) + if (ioc_data.dev_num < 0 || ioc_data.dev_num >= MAX_LEC_ITF) + return -EINVAL; + ioc_data.dev_num = array_index_nospec(ioc_data.dev_num, MAX_LEC_ITF); + if (!dev_lec[ioc_data.dev_num]) return -EINVAL; vpriv = kmalloc(sizeof(struct lec_vcc_priv), GFP_KERNEL); if (!vpriv) -- 2.7.4
