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) Cc: Miklos Szeredi <miklos@xxxxxxxxxx> Cc: linux-unionfs@xxxxxxxxxxxxxxx Reported-by: syzbot+9d14351a171d0d1c7955@xxxxxxxxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/all/000000000000763a6c05e95a5985@xxxxxxxxxx/ Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- 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 87759165d32b..a0e450313ea4 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; -- 2.34.1
