From 522f6e6cba6880a038e2bd88e10390b84cd3febd Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Sat, 23 May 2020 16:21:55 +0300 Subject: ovl: fix out of bounds access warning in ovl_check_fb_len() syzbot reported out of bounds memory access from open_by_handle_at() with a crafted file handle that looks like this: { .handle_bytes = 2, .handle_type = OVL_FILEID_V1 } handle_bytes gets rounded down to 0 and we end up calling: ovl_check_fh_len(fh, 0) => ovl_check_fb_len(fh + 3, -3) But fh buffer is only 2 bytes long, so accessing struct ovl_fb at fh + 3 is illegal. Fixes: cbe7fba8edfc ("ovl: make sure that real fid is 32bit aligned in memory") Reported-and-tested-by: syzbot+61958888b1c60361a791@syzkaller.appspotmail.com Cc: # v5.5 Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi --- fs/overlayfs/overlayfs.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/overlayfs') diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 76747f5b0517..ffbb57b2d7f6 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -355,6 +355,9 @@ int ovl_check_fb_len(struct ovl_fb *fb, int fb_len); static inline int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) { + if (fh_len < sizeof(struct ovl_fh)) + return -EINVAL; + return ovl_check_fb_len(&fh->fb, fh_len - OVL_FH_WIRE_OFFSET); } -- cgit v1.2.3