smb: client: memcpy() with surrounding object base address

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>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index ca50ac6..4858331 100644 (file)
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -5343,7 +5343,7 @@ SetTimesRetry:
        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;