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@xxxxxxxxxxxxxxx Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> --- drivers/usb/gadget/function/f_mass_storage.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c index cb402e7a..043f97a 100644 --- 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" @@ -3152,6 +3154,7 @@ static struct config_group *fsg_lun_make(struct config_group *group, 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]) { -- 2.7.4
