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

[Stephen Rothwell]

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 <s...@canb.auug.org.au>
---
 fs/cifs/cifssmb.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index dc2f4cf08fe9..dcf939cb9d2f 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -601,10 +601,14 @@ CIFSSMBNegotiate(const unsigned int xid, struct cifs_ses 
*ses)
        }
 
        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);
-- 
2.19.0.rc1

-- 
Cheers,
Stephen Rothwell

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