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    Subject[PATCH AUTOSEL 4.18 39/65] fs/cifs: suppress a string overflow warning
    Date
    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>
    ---
    fs/cifs/cifssmb.c | 11 ++++++++---
    1 file changed, 8 insertions(+), 3 deletions(-)

    diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
    index 93408eab92e7..f5baf777564c 100644
    --- a/fs/cifs/cifssmb.c
    +++ b/fs/cifs/cifssmb.c
    @@ -601,10 +601,15 @@ 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);
    --
    2.17.1
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