From cf8aa9bf97cadf85745506c6a3e244b22c268d63 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Sat, 24 Sep 2022 00:33:15 -0700
Subject: [PATCH] ovl: Use "buf" flexible array for memcpy() destination
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 <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
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 e065a5b9a442e..ac9c3ad04016e 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 eee8f08d32b63..e74a610a117ec 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;
--
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