| From 9ae24af3669111d418242caec8dd4ebd9ba26860 Mon Sep 17 00:00:00 2001 |
| From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> |
| Date: Tue, 16 Oct 2018 12:16:45 +0200 |
| Subject: usb: gadget: storage: Fix Spectre v1 vulnerability |
| |
| From: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| |
| commit 9ae24af3669111d418242caec8dd4ebd9ba26860 upstream. |
| |
| num can be 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/usb/gadget/function/f_mass_storage.c:3177 fsg_lun_make() warn: |
| potential spectre issue 'fsg_opts->common->luns' [r] (local cap) |
| |
| Fix this by sanitizing num before using it to index |
| fsg_opts->common->luns |
| |
| 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: stable@vger.kernel.org |
| Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| Acked-by: Felipe Balbi <felipe.balbi@intel.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/usb/gadget/function/f_mass_storage.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| --- a/drivers/usb/gadget/function/f_mass_storage.c |
| +++ b/drivers/usb/gadget/function/f_mass_storage.c |
| @@ -221,6 +221,8 @@ |
| #include <linux/usb/gadget.h> |
| #include <linux/usb/composite.h> |
| |
| +#include <linux/nospec.h> |
| + |
| #include "configfs.h" |
| |
| |
| @@ -3170,6 +3172,7 @@ static struct config_group *fsg_lun_make |
| fsg_opts = to_fsg_opts(&group->cg_item); |
| if (num >= FSG_MAX_LUNS) |
| return ERR_PTR(-ERANGE); |
| + num = array_index_nospec(num, FSG_MAX_LUNS); |
| |
| mutex_lock(&fsg_opts->lock); |
| if (fsg_opts->refcnt || fsg_opts->common->luns[num]) { |
