sunrpc: make debugfs file creation failure non-fatal

v2: gracefully handle the case where some dentry pointers end up NULL
    and be more dilligent about zeroing out dentry pointers

We currently have a problem that SELinux policy is being enforced when
creating debugfs files. If a debugfs file is created as a side effect of
doing some syscall, then that creation can fail if the SELinux policy
for that process prevents it.

This seems wrong. We don't do that for files under /proc, for instance,
so Bruce has proposed a patch to fix that.

While discussing that patch however, Greg K.H. stated:

    "No kernel code should care / fail if a debugfs function fails, so
     please fix up the sunrpc code first."

This patch converts all of the sunrpc debugfs setup code to be void
return functins, and the callers to not look for errors from those
functions.

This should allow rpc_clnt and rpc_xprt creation to work, even if the
kernel fails to create debugfs files for some reason.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h
index c57d8ea0716cddea1419a37481dbd7704b230d65..59a7889e15db51c3b24bc771dbe5d0b1c965212d 100644 (file)
--- a/include/linux/sunrpc/debug.h
+++ b/include/linux/sunrpc/debug.h
@@ -60,17 +60,17 @@ struct rpc_xprt;
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 void           rpc_register_sysctl(void);
 void           rpc_unregister_sysctl(void);
-int            sunrpc_debugfs_init(void);
+void           sunrpc_debugfs_init(void);
 void           sunrpc_debugfs_exit(void);
-int            rpc_clnt_debugfs_register(struct rpc_clnt *);
+void           rpc_clnt_debugfs_register(struct rpc_clnt *);
 void           rpc_clnt_debugfs_unregister(struct rpc_clnt *);
-int            rpc_xprt_debugfs_register(struct rpc_xprt *);
+void           rpc_xprt_debugfs_register(struct rpc_xprt *);
 void           rpc_xprt_debugfs_unregister(struct rpc_xprt *);
 #else
-static inline int
+static inline void
 sunrpc_debugfs_init(void)
 {
-       return 0;
+       return;
 }
 
 static inline void
@@ -79,10 +79,10 @@ sunrpc_debugfs_exit(void)
        return;
 }
 
-static inline int
+static inline void
 rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
 {
-       return 0;
+       return;
 }
 
 static inline void
@@ -91,10 +91,10 @@ rpc_clnt_debugfs_unregister(struct rpc_clnt *clnt)
        return;
 }
 
-static inline int
+static inline void
 rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
 {
-       return 0;
+       return;
 }
 
 static inline void

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 612aa73bbc60c990a320054e4bd7d2846575428e..e6ce1517367f884608640b2532080ab6566b9379 100644 (file)
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -303,9 +303,7 @@ static int rpc_client_register(struct rpc_clnt *clnt,
        struct super_block *pipefs_sb;
        int err;
 
-       err = rpc_clnt_debugfs_register(clnt);
-       if (err)
-               return err;
+       rpc_clnt_debugfs_register(clnt);
 
        pipefs_sb = rpc_get_sb_net(net);
        if (pipefs_sb) {

diff --git a/net/sunrpc/debugfs.c b/net/sunrpc/debugfs.c
index e811f390f9f67ceb2e897ee8da79189417eacc75..82962f7e6e888f619ad79754f038732d5d5b6333 100644 (file)
--- a/net/sunrpc/debugfs.c
+++ b/net/sunrpc/debugfs.c
@@ -129,48 +129,52 @@ static const struct file_operations tasks_fops = {
        .release        = tasks_release,
 };
 
-int
+void
 rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
 {
-       int len, err;
+       int len;
        char name[24]; /* enough for "../../rpc_xprt/ + 8 hex digits + NULL */
+       struct rpc_xprt *xprt;
 
        /* Already registered? */
-       if (clnt->cl_debugfs)
-               return 0;
+       if (clnt->cl_debugfs || !rpc_clnt_dir)
+               return;
 
        len = snprintf(name, sizeof(name), "%x", clnt->cl_clid);
        if (len >= sizeof(name))
-               return -EINVAL;
+               return;
 
        /* make the per-client dir */
        clnt->cl_debugfs = debugfs_create_dir(name, rpc_clnt_dir);
        if (!clnt->cl_debugfs)
-               return -ENOMEM;
+               return;
 
        /* make tasks file */
-       err = -ENOMEM;
        if (!debugfs_create_file("tasks", S_IFREG | S_IRUSR, clnt->cl_debugfs,
                                 clnt, &tasks_fops))
                goto out_err;
 
-       err = -EINVAL;
        rcu_read_lock();
+       xprt = rcu_dereference(clnt->cl_xprt);
+       /* no "debugfs" dentry? Don't bother with the symlink. */
+       if (!xprt->debugfs) {
+               rcu_read_unlock();
+               return;
+       }
        len = snprintf(name, sizeof(name), "../../rpc_xprt/%s",
-                       rcu_dereference(clnt->cl_xprt)->debugfs->d_name.name);
+                       xprt->debugfs->d_name.name);
        rcu_read_unlock();
+
        if (len >= sizeof(name))
                goto out_err;
 
-       err = -ENOMEM;
        if (!debugfs_create_symlink("xprt", clnt->cl_debugfs, name))
                goto out_err;
 
-       return 0;
+       return;
 out_err:
        debugfs_remove_recursive(clnt->cl_debugfs);
        clnt->cl_debugfs = NULL;
-       return err;
 }
 
 void
@@ -226,33 +230,33 @@ static const struct file_operations xprt_info_fops = {
        .release        = xprt_info_release,
 };
 
-int
+void
 rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
 {
        int len, id;
        static atomic_t cur_id;
        char            name[9]; /* 8 hex digits + NULL term */
 
+       if (!rpc_xprt_dir)
+               return;
+
        id = (unsigned int)atomic_inc_return(&cur_id);
 
        len = snprintf(name, sizeof(name), "%x", id);
        if (len >= sizeof(name))
-               return -EINVAL;
+               return;
 
        /* make the per-client dir */
        xprt->debugfs = debugfs_create_dir(name, rpc_xprt_dir);
        if (!xprt->debugfs)
-               return -ENOMEM;
+               return;
 
        /* make tasks file */
        if (!debugfs_create_file("info", S_IFREG | S_IRUSR, xprt->debugfs,
                                 xprt, &xprt_info_fops)) {
                debugfs_remove_recursive(xprt->debugfs);
                xprt->debugfs = NULL;
-               return -ENOMEM;
        }
-
-       return 0;
 }
 
 void
@@ -266,14 +270,17 @@ void __exit
 sunrpc_debugfs_exit(void)
 {
        debugfs_remove_recursive(topdir);
+       topdir = NULL;
+       rpc_clnt_dir = NULL;
+       rpc_xprt_dir = NULL;
 }
 
-int __init
+void __init
 sunrpc_debugfs_init(void)
 {
        topdir = debugfs_create_dir("sunrpc", NULL);
        if (!topdir)
-               goto out;
+               return;
 
        rpc_clnt_dir = debugfs_create_dir("rpc_clnt", topdir);
        if (!rpc_clnt_dir)
@@ -283,10 +290,9 @@ sunrpc_debugfs_init(void)
        if (!rpc_xprt_dir)
                goto out_remove;
 
-       return 0;
+       return;
 out_remove:
        debugfs_remove_recursive(topdir);
        topdir = NULL;
-out:
-       return -ENOMEM;
+       rpc_clnt_dir = NULL;
 }

diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
index e37fbed879568da535aa540656e7b7ace508e2cb..ee5d3d253102bf5d81a39f953248a6a6ca7a38d6 100644 (file)
--- a/net/sunrpc/sunrpc_syms.c
+++ b/net/sunrpc/sunrpc_syms.c
@@ -98,10 +98,7 @@ init_sunrpc(void)
        if (err)
                goto out4;
 
-       err = sunrpc_debugfs_init();
-       if (err)
-               goto out5;
-
+       sunrpc_debugfs_init();
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
        rpc_register_sysctl();
 #endif
@@ -109,8 +106,6 @@ init_sunrpc(void)
        init_socket_xprt();     /* clnt sock transport */
        return 0;
 
-out5:
-       unregister_rpc_pipefs();
 out4:
        unregister_pernet_subsys(&sunrpc_net_ops);
 out3:

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index e3015aede0d9443d99eba6b820aed104ab7515a6..9949722d99cebf6afa15953d8a9ac6a5c0bc2824 100644 (file)
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1331,7 +1331,6 @@ static void xprt_init(struct rpc_xprt *xprt, struct net *net)
  */
 struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
 {
-       int err;
        struct rpc_xprt *xprt;
        struct xprt_class *t;
 
@@ -1372,11 +1371,7 @@ found:
                return ERR_PTR(-ENOMEM);
        }
 
-       err = rpc_xprt_debugfs_register(xprt);
-       if (err) {
-               xprt_destroy(xprt);
-               return ERR_PTR(err);
-       }
+       rpc_xprt_debugfs_register(xprt);
 
        dprintk("RPC:       created transport %p with %u slots\n", xprt,
                        xprt->max_reqs);