[PATCH][V2][cifs-next] cifs: fix dereference on ses before it is null checked

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

The assignment of pointer server dereferences pointer ses, however,
this dereference occurs before ses is null checked and hence we
have a potential null pointer dereference.  Fix this by only
dereferencing ses after it has been null checked.

Addresses-Coverity: ("Dereference before null check")
Fixes: 2808c6639104 ("cifs: add new debugging macro cifs_server_dbg")
Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 fs/cifs/smb2pdu.c   | 11 ++++++++---
 fs/cifs/transport.c |  3 ++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index dbc6ef50dd45..0e92983de0b7 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -2759,8 +2759,10 @@ SMB2_ioctl(const unsigned int xid, struct cifs_tcon 
*tcon, u64 persistent_fid,
        else
                return -EIO;
 
+       if (!ses)
+               return -EIO;
        server = ses->server;
-       if (!ses || !(server))
+       if (!server)
                return -EIO;
 
        if (smb3_encryption_required(tcon))
@@ -3058,13 +3060,16 @@ query_info(const unsigned int xid, struct cifs_tcon 
*tcon,
        int rc = 0;
        int resp_buftype = CIFS_NO_BUFFER;
        struct cifs_ses *ses = tcon->ses;
-       struct TCP_Server_Info *server = ses->server;
+       struct TCP_Server_Info *server;
        int flags = 0;
        bool allocated = false;
 
        cifs_dbg(FYI, "Query Info\n");
 
-       if (!ses || !(server))
+       if (!ses)
+               return -EIO;
+       server = ses->server;
+       if (!server)
                return -EIO;
 
        if (smb3_encryption_required(tcon))
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 0d60bd2f4dca..a90bd4d75b4d 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -1242,12 +1242,13 @@ SendReceive(const unsigned int xid, struct cifs_ses 
*ses,
        struct kvec iov = { .iov_base = in_buf, .iov_len = len };
        struct smb_rqst rqst = { .rq_iov = &iov, .rq_nvec = 1 };
        struct cifs_credits credits = { .value = 1, .instance = 0 };
-       struct TCP_Server_Info *server = ses->server;
+       struct TCP_Server_Info *server;
 
        if (ses == NULL) {
                cifs_dbg(VFS, "Null smb session\n");
                return -EIO;
        }
+       server = ses->server;
        if (server == NULL) {
                cifs_dbg(VFS, "Null tcp session\n");
                return -EIO;
-- 
2.20.1