From: Amir Goldstein amir73il@gmail.com
commit 522f6e6cba6880a038e2bd88e10390b84cd3febd upstream.
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: stable@vger.kernel.org # v5.5 Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/overlayfs/overlayfs.h | 3 +++ 1 file changed, 3 insertions(+)
--- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -355,6 +355,9 @@ int ovl_check_fb_len(struct ovl_fb *fb,
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); }