linux-hardening - [PATCH] cifs: Avoid field over-reading memcpy()

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Date:   Mon, 21 Jun 2021 14:44:46 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Steve French <stfrench@...rosoft.com>
Cc:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
        linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH] cifs: Avoid field over-reading memcpy()

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally reading across neighboring fields.

Instead of using memcpy to read across multiple struct members, just
perform per-member assignments as already done for other members.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/cifs/smb2pdu.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 31784e3fa96f..962826dc3316 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -2892,7 +2892,10 @@ SMB2_open(const unsigned int xid, struct cifs_open_parms *oparms, __le16 *path,
 #endif /* CIFS_DEBUG2 */
 
 	if (buf) {
-		memcpy(buf, &rsp->CreationTime, 32);
+		buf->CreationTime = rsp->CreationTime;
+		buf->LastAccessTime = rsp->LastAccessTime;
+		buf->LastWriteTime = rsp->LastWriteTime;
+		buf->ChangeTime = rsp->ChangeTime;
 		buf->AllocationSize = rsp->AllocationSize;
 		buf->EndOfFile = rsp->EndofFile;
 		buf->Attributes = rsp->FileAttributes;
-- 
2.30.2