Thanks for pointing this out.  I don't think tcon->ses can be null
here but might as well add the check in a consistent way to avoid
confusion and static checker warnings

On Sat, May 2, 2020 at 8:32 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> Hello Aurelien Aptel,
>
> The patch feeaec621c09: "cifs: multichannel: move channel selection
> above transport layer" from Apr 24, 2020, leads to the following
> static checker warning:
>
>         fs/cifs/smb2pdu.c:149 smb2_hdr_assemble()
>         error: we previously assumed 'tcon->ses' could be null (see line 133)
>
> fs/cifs/smb2pdu.c
>    120          shdr->ProcessId = cpu_to_le32((__u16)current->tgid);
>    121
>    122          if (!tcon)
>    123                  goto out;
>    124
>    125          /* GLOBAL_CAP_LARGE_MTU will only be set if dialect > SMB2.02 */
>    126          /* See sections 2.2.4 and 3.2.4.1.5 of MS-SMB2 */
>    127          if (server && (server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
>    128                  shdr->CreditCharge = cpu_to_le16(1);
>    129          /* else CreditCharge MBZ */
>    130
>    131          shdr->TreeId = tcon->tid;
>    132          /* Uid is not converted */
>    133          if (tcon->ses)
>                     ^^^^^^^^^
> Check for NULL.
>
>    134                  shdr->SessionId = tcon->ses->Suid;
>    135
>    136          /*
>    137           * If we would set SMB2_FLAGS_DFS_OPERATIONS on open we also would have
>    138           * to pass the path on the Open SMB prefixed by \\server\share.
>    139           * Not sure when we would need to do the augmented path (if ever) and
>    140           * setting this flag breaks the SMB2 open operation since it is
>    141           * illegal to send an empty path name (without \\server\share prefix)
>    142           * when the DFS flag is set in the SMB open header. We could
>    143           * consider setting the flag on all operations other than open
>    144           * but it is safer to net set it for now.
>    145           */
>    146  /*      if (tcon->share_flags & SHI1005_FLAGS_DFS)
>    147                  shdr->Flags |= SMB2_FLAGS_DFS_OPERATIONS; */
>    148
>    149          if (server && server->sign && !smb3_encryption_required(tcon))
>                                                                         ^^^^
> Unchecked dereference inside the function.  There used to be a bunch
> of checks for NULL "tcon->ses" but some of them were replaces with a
> check for "server" instead.
>
>    150                  shdr->Flags |= SMB2_FLAGS_SIGNED;
>    151  out:
>    152          return;
>    153  }
>
> regards,
> dan carpenter



-- 
Thanks,

Steve