Re: [PATCH] smb: client: memcpy() with surrounding object base address

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

On 17/11/24 05:32, Kees Cook wrote:
> Like commit f1f047bd7ce0 ("smb: client: Fix -Wstringop-overflow issues"),
> adjust the memcpy() destination address to be based off the surrounding
> object rather than based off the 4-byte "Protocol" member. This avoids a
> build-time warning when compiling under CONFIG_FORTIFY_SOURCE with GCC 15:
> 
> In function 'fortify_memcpy_chk',
>      inlined from 'CIFSSMBSetPathInfo' at ../fs/smb/client/cifssmb.c:5358:2:
> ../include/linux/fortify-string.h:571:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
>    571 |                         __write_overflow_field(p_size_field, size);
>        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Signed-off-by: Kees Cook <kees@kernel.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
-Gustavo

> ---
> Cc: Steve French <sfrench@samba.org>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: Paulo Alcantara <pc@manguebit.com>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: linux-cifs@vger.kernel.org
> Cc: samba-technical@lists.samba.org
> ---
>   fs/smb/client/cifssmb.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
> index b96ca9be5352..026d6b5f23a9 100644
> --- a/fs/smb/client/cifssmb.c
> +++ b/fs/smb/client/cifssmb.c
> @@ -5337,7 +5337,7 @@ CIFSSMBSetPathInfo(const unsigned int xid, struct cifs_tcon *tcon,
>   	param_offset = offsetof(struct smb_com_transaction2_spi_req,
>   				InformationLevel) - 4;
>   	offset = param_offset + params;
> -	data_offset = (char *) (&pSMB->hdr.Protocol) + offset;
> +	data_offset = (char *)pSMB + offsetof(typeof(*pSMB), hdr.Protocol) + offset;
>   	pSMB->ParameterOffset = cpu_to_le16(param_offset);
>   	pSMB->DataOffset = cpu_to_le16(offset);
>   	pSMB->SetupCount = 1;