[PATCH 3.18 086/120] fs/cifs: suppress a string overflow warning

Greg Kroah-Hartman
2018-10-11T15:39:36Z

From: Stephen Rothwell <sfr@canb.auug.org.au>

[ Upstream commit bcfb84a996f6fa90b5e6e2954b2accb7a4711097 ]

A powerpc build of cifs with gcc v8.2.0 produces this warning:

fs/cifs/cifssmb.c: In function ‘CIFSSMBNegotiate’:
fs/cifs/cifssmb.c:605:3: warning: ‘strncpy’ writing 16 bytes into a region of size 1 overflows the destination [-Wstringop-overflow=]
strncpy(pSMB->DialectsArray+count, protocols[i].name, 16);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Since we are already doing a strlen() on the source, change the strncpy
to a memcpy().

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/cifssmb.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -577,10 +577,15 @@ CIFSSMBNegotiate(const unsigned int xid,
}

count = 0;
+ /*
+ * We know that all the name entries in the protocols array
+ * are short (< 16 bytes anyway) and are NUL terminated.
+ */
for (i = 0; i < CIFS_NUM_PROT; i++) {
- strncpy(pSMB->DialectsArray+count, protocols[i].name, 16);
- count += strlen(protocols[i].name) + 1;
- /* null at end of source and target buffers anyway */
+ size_t len = strlen(protocols[i].name) + 1;
+
+ memcpy(pSMB->DialectsArray+count, protocols[i].name, len);
+ count += len;
}
inc_rfc1001_len(pSMB, count);
pSMB->ByteCount = cpu_to_le16(count);