From 07a96977b2f462337a9121302de64277b8747ab1 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Sat, 24 Sep 2022 00:33:15 -0700 Subject: [PATCH] ovl: Use "buf" flexible array for memcpy() destination commit cf8aa9bf97cadf85745506c6a3e244b22c268d63 upstream. The "buf" flexible array needs to be the memcpy() destination to avoid false positive run-time warning from the recent FORTIFY_SOURCE hardening: memcpy: detected field-spanning write (size 93) of single field "&fh->fb" at fs/overlayfs/export.c:799 (size 21) Reported-by: syzbot+9d14351a171d0d1c7955@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/000000000000763a6c05e95a5985@google.com/ Signed-off-by: Kees Cook Reviewed-by: Gustavo A. R. Silva Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/export.c | 2 +- fs/overlayfs/overlayfs.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index e065a5b9a442..ac9c3ad04016 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -796,7 +796,7 @@ static struct ovl_fh *ovl_fid_to_fh(struct fid *fid, int buflen, int fh_type) return ERR_PTR(-ENOMEM); /* Copy unaligned inner fh into aligned buffer */ - memcpy(&fh->fb, fid, buflen - OVL_FH_WIRE_OFFSET); + memcpy(fh->buf, fid, buflen - OVL_FH_WIRE_OFFSET); return fh; } diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index eee8f08d32b6..e74a610a117e 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -108,7 +108,7 @@ struct ovl_fh { u8 padding[3]; /* make sure fb.fid is 32bit aligned */ union { struct ovl_fb fb; - u8 buf[0]; + DECLARE_FLEX_ARRAY(u8, buf); }; } __packed;