| Message ID | 20220924073315.3593031-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | cf8aa9bf97cadf85745506c6a3e244b22c268d63 |
| Headers | show |
| Series | ovl: Use "buf" flexible array for memcpy() destination | expand |
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@szeredi.hu> > Cc: linux-unionfs@vger.kernel.org > Reported-by: syzbot+9d14351a171d0d1c7955@syzkaller.appspotmail.com > Link: https://lore.kernel.org/all/000000000000763a6c05e95a5985@google.com/ > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> 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 >
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;
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@szeredi.hu> Cc: linux-unionfs@vger.kernel.org Reported-by: syzbot+9d14351a171d0d1c7955@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/000000000000763a6c05e95a5985@google.com/ Signed-off-by: Kees Cook <keescook@chromium.org> --- fs/overlayfs/export.c | 2 +- fs/overlayfs/overlayfs.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)