3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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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
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 [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/usb/gadget/f_mass_storage.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/usb/gadget/f_mass_storage.c +++ b/drivers/usb/gadget/f_mass_storage.c @@ -219,6 +219,8 @@ #include <linux/usb/gadget.h> #include <linux/usb/composite.h>
+#include <linux/nospec.h> + #include "gadget_chips.h" #include "configfs.h"
@@ -3344,6 +3346,7 @@ 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]) {