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SubjectRe: [PATCH] fs/cifs: suppress a string overflow warning
Merged into cifs-2.6.git for-next

Is the message annoying enough on powerpc to merit going into
4.19-rc3, presumably should wait for 4.20?
On Sun, Sep 2, 2018 at 10:24 PM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> 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>
> ---
> 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



--
Thanks,

Steve

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