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sunrpc: make debugfs file creation failure non-fatal
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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.

Symptoms were failing krb5 mounts on systems using gss-proxy and
selinux.

Fixes: 388f0c7 "sunrpc: add a debugfs rpc_xprt directory..."
Cc: stable@vger.kernel.org
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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Jeff Layton authored and J. Bruce Fields committed Mar 31, 2015
1 parent f3f0333 commit f9c72d1
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Showing 5 changed files with 41 additions and 47 deletions.
18 changes: 9 additions & 9 deletions include/linux/sunrpc/debug.h
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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
Expand All @@ -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
Expand Down
4 changes: 1 addition & 3 deletions net/sunrpc/clnt.c
Original file line number Diff line number Diff line change
Expand Up @@ -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) {
Expand Down
52 changes: 29 additions & 23 deletions net/sunrpc/debugfs.c
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand All @@ -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)
Expand All @@ -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;
}
7 changes: 1 addition & 6 deletions net/sunrpc/sunrpc_syms.c
Original file line number Diff line number Diff line change
Expand Up @@ -98,19 +98,14 @@ 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
svc_init_xprt_sock(); /* svc sock transport */
init_socket_xprt(); /* clnt sock transport */
return 0;

out5:
unregister_rpc_pipefs();
out4:
unregister_pernet_subsys(&sunrpc_net_ops);
out3:
Expand Down
7 changes: 1 addition & 6 deletions net/sunrpc/xprt.c
Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand Down Expand Up @@ -1372,11 +1371,7 @@ struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
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);
Expand Down

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