Re: [PATCH] cifs: protect access of TCP_Server_Info::{dstaddr,hostname}

[Steve French <smfrench@gmail.com>]

merged into cifs-2.6.git for-next pending testing

On Thu, Dec 29, 2022 at 3:43 PM Paulo Alcantara <pc@cjr.nz> wrote:
>
> Use the appropriate locks to protect access of hostname and dstaddr
> fields in cifs_tree_connect() as they might get changed by other
> tasks.
>
> Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
> ---
>  fs/cifs/dfs.c  | 22 +++++++++++-----------
>  fs/cifs/misc.c |  2 ++
>  2 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/fs/cifs/dfs.c b/fs/cifs/dfs.c
> index 30086f2060a1..b64d20374b9c 100644
> --- a/fs/cifs/dfs.c
> +++ b/fs/cifs/dfs.c
> @@ -327,8 +327,8 @@ static int update_server_fullpath(struct TCP_Server_Info *server, struct cifs_sb
>         return rc;
>  }
>
> -static int target_share_matches_server(struct TCP_Server_Info *server, const char *tcp_host,
> -                                      size_t tcp_host_len, char *share, bool *target_match)
> +static int target_share_matches_server(struct TCP_Server_Info *server, char *share,
> +                                      bool *target_match)
>  {
>         int rc = 0;
>         const char *dfs_host;
> @@ -338,13 +338,16 @@ static int target_share_matches_server(struct TCP_Server_Info *server, const cha
>         extract_unc_hostname(share, &dfs_host, &dfs_host_len);
>
>         /* Check if hostnames or addresses match */
> -       if (dfs_host_len != tcp_host_len || strncasecmp(dfs_host, tcp_host, dfs_host_len) != 0) {
> -               cifs_dbg(FYI, "%s: %.*s doesn't match %.*s\n", __func__, (int)dfs_host_len,
> -                        dfs_host, (int)tcp_host_len, tcp_host);
> +       cifs_server_lock(server);
> +       if (dfs_host_len != strlen(server->hostname) ||
> +           strncasecmp(dfs_host, server->hostname, dfs_host_len)) {
> +               cifs_dbg(FYI, "%s: %.*s doesn't match %s\n", __func__,
> +                        (int)dfs_host_len, dfs_host, server->hostname);
>                 rc = match_target_ip(server, dfs_host, dfs_host_len, target_match);
>                 if (rc)
>                         cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
>         }
> +       cifs_server_unlock(server);
>         return rc;
>  }
>
> @@ -358,13 +361,9 @@ static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *t
>         struct cifs_ses *root_ses = CIFS_DFS_ROOT_SES(tcon->ses);
>         struct cifs_tcon *ipc = root_ses->tcon_ipc;
>         char *share = NULL, *prefix = NULL;
> -       const char *tcp_host;
> -       size_t tcp_host_len;
>         struct dfs_cache_tgt_iterator *tit;
>         bool target_match;
>
> -       extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
> -
>         tit = dfs_cache_get_tgt_iterator(tl);
>         if (!tit) {
>                 rc = -ENOENT;
> @@ -387,8 +386,7 @@ static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *t
>                         break;
>                 }
>
> -               rc = target_share_matches_server(server, tcp_host, tcp_host_len, share,
> -                                                &target_match);
> +               rc = target_share_matches_server(server, share, &target_match);
>                 if (rc)
>                         break;
>                 if (!target_match) {
> @@ -497,7 +495,9 @@ int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const stru
>         }
>
>         if (tcon->ipc) {
> +               cifs_server_lock(server);
>                 scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
> +               cifs_server_unlock(server);
>                 rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
>                 goto out;
>         }
> diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
> index 4d3c586785a5..2a19c7987c5b 100644
> --- a/fs/cifs/misc.c
> +++ b/fs/cifs/misc.c
> @@ -1277,7 +1277,9 @@ int match_target_ip(struct TCP_Server_Info *server,
>         if (rc < 0)
>                 return rc;
>
> +       spin_lock(&server->srv_lock);
>         *result = cifs_match_ipaddr((struct sockaddr *)&server->dstaddr, (struct sockaddr *)&ss);
> +       spin_unlock(&server->srv_lock);
>         cifs_dbg(FYI, "%s: ip addresses match: %u\n", __func__, *result);
>         return 0;
>  }
> --
> 2.39.0
>


-- 
Thanks,

Steve