On Sat, Sep 24, 2022 at 12:33:15AM -0700, Kees Cook wrote: > 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> Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> Thanks! -- Gustavo > --- > 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 >
