From f6b7a635a06a5f8eb94b7f4ec8a63ba7c227bcd7 Mon Sep 17 00:00:00 2001 From: Denis Efremov Date: Fri, 12 Jul 2019 21:55:23 +0300 Subject: [PATCH] floppy: fix out-of-bounds read in copy_buffer commit da99466ac243f15fbba65bd261bfc75ffa1532b6 upstream. This fixes a global out-of-bounds read access in the copy_buffer function of the floppy driver. The FDDEFPRM ioctl allows one to set the geometry of a disk. The sect and head fields (unsigned int) of the floppy_drive structure are used to compute the max_sector (int) in the make_raw_rw_request function. It is possible to overflow the max_sector. Next, max_sector is passed to the copy_buffer function and used in one of the memcpy calls. An unprivileged user could trigger the bug if the device is accessible, but requires a floppy disk to be inserted. The patch adds the check for the .sect * .head multiplication for not overflowing in the set_geometry function. The bug was found by syzkaller. Signed-off-by: Denis Efremov Tested-by: Willy Tarreau Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings CVE-2019-14283 Signed-off-by: Kevin F. Haggerty Change-Id: Idb3e900d17920e6339b862419018f4740a7d4caf --- drivers/block/floppy.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index bc99e5c68d7..cefd2e60aaa 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3224,8 +3224,10 @@ static int set_geometry(unsigned int cmd, struct floppy_struct *g, int cnt; /* sanity checking for parameters. */ - if (g->sect <= 0 || - g->head <= 0 || + if ((int)g->sect <= 0 || + (int)g->head <= 0 || + /* check for overflow in max_sector */ + (int)(g->sect * g->head) <= 0 || g->track <= 0 || g->track > UDP->tracks >> STRETCH(g) || /* check if reserved bits are set */ (g->stretch & ~(FD_STRETCH | FD_SWAPSIDES | FD_SECTBASEMASK)) != 0)