4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jinbum Park jinb.park7@gmail.com
[ Upstream commit 55690c07b44a82cc3359ce0c233f4ba7d80ba145 ]
User controls @dev_minor which to be used as index of pkt_devs. So, It can be exploited via Spectre-like attack. (speculative execution)
This kind of attack leaks address of pkt_devs, [1] It leads an attacker to bypass security mechanism such as KASLR.
So sanitize @dev_minor before using it to prevent attack.
[1] https://github.com/jinb-park/linux-exploit/ tree/master/exploit-remaining-spectre-gadget/leak_pkt_devs.c
Signed-off-by: Jinbum Park jinb.park7@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/block/pktcdvd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/block/pktcdvd.c +++ b/drivers/block/pktcdvd.c @@ -67,7 +67,7 @@ #include <scsi/scsi.h> #include <linux/debugfs.h> #include <linux/device.h> - +#include <linux/nospec.h> #include <linux/uaccess.h>
#define DRIVER_NAME "pktcdvd" @@ -2231,6 +2231,8 @@ static struct pktcdvd_device *pkt_find_d { if (dev_minor >= MAX_WRITERS) return NULL; + + dev_minor = array_index_nospec(dev_minor, MAX_WRITERS); return pkt_devs[dev_minor]; }