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@xxxxxxxxx> --- drivers/block/pktcdvd.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c index c61d20c..665760d 100644 --- a/drivers/block/pktcdvd.c +++ b/drivers/block/pktcdvd.c @@ -67,8 +67,8 @@ #include <scsi/scsi.h> #include <linux/debugfs.h> #include <linux/device.h> - #include <linux/uaccess.h> +#include <linux/nospec.h> #define DRIVER_NAME "pktcdvd" @@ -2229,9 +2229,13 @@ static void pkt_release_dev(struct pktcdvd_device *pd, int flush) static struct pktcdvd_device *pkt_find_dev_from_minor(unsigned int dev_minor) { + unsigned int idx = 0; + if (dev_minor >= MAX_WRITERS) return NULL; - return pkt_devs[dev_minor]; + + idx = array_index_nospec(dev_minor, MAX_WRITERS); + return pkt_devs[idx]; } static int pkt_open(struct block_device *bdev, fmode_t mode) -- 1.9.1
