From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: fbdev: color map copying bounds checking Copying color maps to userspace doesn't check the value of to->start, which will cause kernel heap buffer OOB read due to signedness wraps. CVE-2016-8405 Link: http://lkml.kernel.org/r/20170105224249.GA50925@beast Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Reported-by: Peter Pi (@heisecode) of Trend Micro Cc: Min Chong <mchong@xxxxxxxxxx> Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/video/fbdev/core/fbcmap.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff -puN drivers/video/fbdev/core/fbcmap.c~fbdev-color-map-copying-bounds-checking drivers/video/fbdev/core/fbcmap.c --- a/drivers/video/fbdev/core/fbcmap.c~fbdev-color-map-copying-bounds-checking +++ a/drivers/video/fbdev/core/fbcmap.c @@ -163,17 +163,18 @@ void fb_dealloc_cmap(struct fb_cmap *cma int fb_copy_cmap(const struct fb_cmap *from, struct fb_cmap *to) { - int tooff = 0, fromoff = 0; - int size; + unsigned int tooff = 0, fromoff = 0; + size_t size; if (to->start > from->start) fromoff = to->start - from->start; else tooff = from->start - to->start; - size = to->len - tooff; - if (size > (int) (from->len - fromoff)) - size = from->len - fromoff; - if (size <= 0) + if (fromoff >= from->len || tooff >= to->len) + return -EINVAL; + + size = min_t(size_t, to->len - tooff, from->len - fromoff); + if (size == 0) return -EINVAL; size *= sizeof(u16); @@ -187,17 +188,18 @@ int fb_copy_cmap(const struct fb_cmap *f int fb_cmap_to_user(const struct fb_cmap *from, struct fb_cmap_user *to) { - int tooff = 0, fromoff = 0; - int size; + unsigned int tooff = 0, fromoff = 0; + size_t size; if (to->start > from->start) fromoff = to->start - from->start; else tooff = from->start - to->start; - size = to->len - tooff; - if (size > (int) (from->len - fromoff)) - size = from->len - fromoff; - if (size <= 0) + if (fromoff >= from->len || tooff >= to->len) + return -EINVAL; + + size = min_t(size_t, to->len - tooff, from->len - fromoff); + if (size == 0) return -EINVAL; size *= sizeof(u16); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
