net: Providing protocol type via system.sockprotoname xattr of /proc/PID/fd entries

lsof reports some of socket descriptors as "can't identify protocol" like: [yamato@localhost]/tmp% sudo lsof | grep dbus | grep iden dbus-daem 652 dbus 6u sock ... 17812 can't identify protocol dbus-daem 652 dbus 34u sock ... 24689 can't identify protocol dbus-daem 652 dbus 42u sock ... 24739 can't identify protocol dbus-daem 652 dbus 48u sock ... 22329 can't identify protocol ... lsof cannot resolve the protocol used in a socket because procfs doesn't provide the map between inode number on sockfs and protocol type of the socket. For improving the situation this patch adds an extended attribute named 'system.sockprotoname' in which the protocol name for /proc/PID/fd/SOCKET is stored. So lsof can know the protocol for a given /proc/PID/fd/SOCKET with getxattr system call. A few weeks ago I submitted a patch for the same purpose. The patch was introduced /proc/net/sockfs which enumerates inodes and protocols of all sockets alive on a system. However, it was rejected because (1) a global lock was needed, and (2) the layout of struct socket was changed with the patch. This patch doesn't use any global lock; and doesn't change the layout of any structs. In this patch, a protocol name is stored to dentry->d_name of sockfs when new socket is associated with a file descriptor. Before this patch dentry->d_name was not used; it was just filled with empty string. lsof may use an extended attribute named 'system.sockprotoname' to retrieve the value of dentry->d_name. It is nice if we can see the protocol name with ls -l /proc/PID/fd. However, "socket:[#INODE]", the name format returned from sockfs_dname() was already defined. To keep the compatibility between kernel and user land, the extended attribute is used to prepare the value of dentry->d_name. Signed-off-by: Masatake YAMATO <yamato@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>

net: Providing protocol type via system.sockprotoname xattr of /proc/PID/fd entries
lsof reports some of socket descriptors as "can't identify protocol" like: [yamato@localhost]/tmp% sudo lsof | grep dbus | grep iden dbus-daem 652 dbus 6u sock ... 17812 can't identify protocol dbus-daem 652 dbus 34u sock ... 24689 can't identify protocol dbus-daem 652 dbus 42u sock ... 24739 can't identify protocol dbus-daem 652 dbus 48u sock ... 22329 can't identify protocol ... lsof cannot resolve the protocol used in a socket because procfs doesn't provide the map between inode number on sockfs and protocol type of the socket. For improving the situation this patch adds an extended attribute named 'system.sockprotoname' in which the protocol name for /proc/PID/fd/SOCKET is stored. So lsof can know the protocol for a given /proc/PID/fd/SOCKET with getxattr system call. A few weeks ago I submitted a patch for the same purpose. The patch was introduced /proc/net/sockfs which enumerates inodes and protocols of all sockets alive on a system. However, it was rejected because (1) a global lock was needed, and (2) the layout of struct socket was changed with the patch. This patch doesn't use any global lock; and doesn't change the layout of any structs. In this patch, a protocol name is stored to dentry->d_name of sockfs when new socket is associated with a file descriptor. Before this patch dentry->d_name was not used; it was just filled with empty string. lsof may use an extended attribute named 'system.sockprotoname' to retrieve the value of dentry->d_name. It is nice if we can see the protocol name with ls -l /proc/PID/fd. However, "socket:[#INODE]", the name format returned from sockfs_dname() was already defined. To keep the compatibility between kernel and user land, the extended attribute is used to prepare the value of dentry->d_name. Signed-off-by: Masatake YAMATO <yamato@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Masatake YAMATO · David S. Miller
1 parent cefd81cfec
Showing 1 changed file with 78 additions and 5 deletions Side-by-side Diff
net/socket.c
@@ -88,6 +88,7 @@
 #include <linux/nsproxy.h>
 #include <linux/magic.h>
 #include <linux/slab.h>
+#include <linux/xattr.h>
  
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -346,7 +347,8 @@
  *	but we take care of internal coherence yet.
  */
  
-static int sock_alloc_file(struct socket *sock, struct file **f, int flags)
+static int sock_alloc_file(struct socket *sock, struct file **f, int flags,
+			   const char *dname)
 {
 	struct qstr name = { .name = "" };
 	struct path path;
@@ -357,6 +359,13 @@
 	if (unlikely(fd < 0))
 		return fd;
  
+	if (dname) {
+		name.name = dname;
+		name.len = strlen(name.name);
+	} else if (sock->sk) {
+		name.name = sock->sk->sk_prot_creator->name;
+		name.len = strlen(name.name);
+	}
 	path.dentry = d_alloc_pseudo(sock_mnt->mnt_sb, &name);
 	if (unlikely(!path.dentry)) {
 		put_unused_fd(fd);
@@ -389,7 +398,7 @@
 int sock_map_fd(struct socket *sock, int flags)
 {
 	struct file *newfile;
-	int fd = sock_alloc_file(sock, &newfile, flags);
+	int fd = sock_alloc_file(sock, &newfile, flags, NULL);
  
 	if (likely(fd >= 0))
 		fd_install(fd, newfile);
@@ -455,6 +464,68 @@
 	return NULL;
 }
  
+#define XATTR_SOCKPROTONAME_SUFFIX "sockprotoname"
+#define XATTR_NAME_SOCKPROTONAME (XATTR_SYSTEM_PREFIX XATTR_SOCKPROTONAME_SUFFIX)
+#define XATTR_NAME_SOCKPROTONAME_LEN (sizeof(XATTR_NAME_SOCKPROTONAME)-1)
+static ssize_t sockfs_getxattr(struct dentry *dentry,
+			       const char *name, void *value, size_t size)
+{
+	const char *proto_name;
+	size_t proto_size;
+	int error;
+
+	error = -ENODATA;
+	if (!strncmp(name, XATTR_NAME_SOCKPROTONAME, XATTR_NAME_SOCKPROTONAME_LEN)) {
+		proto_name = dentry->d_name.name;
+		proto_size = strlen(proto_name);
+
+		if (value) {
+			error = -ERANGE;
+			if (proto_size + 1 > size)
+				goto out;
+
+			strncpy(value, proto_name, proto_size + 1);
+		}
+		error = proto_size + 1;
+	}
+
+out:
+	return error;
+}
+
+static ssize_t sockfs_listxattr(struct dentry *dentry, char *buffer,
+				size_t size)
+{
+	ssize_t len;
+	ssize_t used = 0;
+
+	len = security_inode_listsecurity(dentry->d_inode, buffer, size);
+	if (len < 0)
+		return len;
+	used += len;
+	if (buffer) {
+		if (size < used)
+			return -ERANGE;
+		buffer += len;
+	}
+
+	len = (XATTR_NAME_SOCKPROTONAME_LEN + 1);
+	used += len;
+	if (buffer) {
+		if (size < used)
+			return -ERANGE;
+		memcpy(buffer, XATTR_NAME_SOCKPROTONAME, len);
+		buffer += len;
+	}
+
+	return used;
+}
+
+static const struct inode_operations sockfs_inode_ops = {
+	.getxattr = sockfs_getxattr,
+	.listxattr = sockfs_listxattr,
+};
+
 /**
  *	sock_alloc	-	allocate a socket
  *
@@ -479,6 +550,7 @@
 	inode->i_mode = S_IFSOCK | S_IRWXUGO;
 	inode->i_uid = current_fsuid();
 	inode->i_gid = current_fsgid();
+	inode->i_op = &sockfs_inode_ops;
  
 	this_cpu_add(sockets_in_use, 1);
 	return sock;
  
@@ -1394,13 +1466,13 @@
 	if (err < 0)
 		goto out_release_both;
  
-	fd1 = sock_alloc_file(sock1, &newfile1, flags);
+	fd1 = sock_alloc_file(sock1, &newfile1, flags, NULL);
 	if (unlikely(fd1 < 0)) {
 		err = fd1;
 		goto out_release_both;
 	}
  
-	fd2 = sock_alloc_file(sock2, &newfile2, flags);
+	fd2 = sock_alloc_file(sock2, &newfile2, flags, NULL);
 	if (unlikely(fd2 < 0)) {
 		err = fd2;
 		fput(newfile1);
@@ -1536,7 +1608,8 @@
 	 */
 	__module_get(newsock->ops->owner);
  
-	newfd = sock_alloc_file(newsock, &newfile, flags);
+	newfd = sock_alloc_file(newsock, &newfile, flags,
+				sock->sk->sk_prot_creator->name);
 	if (unlikely(newfd < 0)) {
 		err = newfd;
 		sock_release(newsock);
...	...	@@ -88,6 +88,7 @@
88	88	#include <linux/nsproxy.h>
89	89	#include <linux/magic.h>
90	90	#include <linux/slab.h>
	91	+#include <linux/xattr.h>
91	92
92	93	#include <asm/uaccess.h>
93	94	#include <asm/unistd.h>
...	...	@@ -346,7 +347,8 @@
346	347	* but we take care of internal coherence yet.
347	348	*/
348	349
349		-static int sock_alloc_file(struct socket sock, struct file *f, int flags)
	350	+static int sock_alloc_file(struct socket sock, struct file *f, int flags,
	351	+ const char *dname)
350	352	{
351	353	struct qstr name = { .name = "" };
352	354	struct path path;
...	...	@@ -357,6 +359,13 @@
357	359	if (unlikely(fd < 0))
358	360	return fd;
359	361
	362	+ if (dname) {
	363	+ name.name = dname;
	364	+ name.len = strlen(name.name);
	365	+ } else if (sock->sk) {
	366	+ name.name = sock->sk->sk_prot_creator->name;
	367	+ name.len = strlen(name.name);
	368	+ }
360	369	path.dentry = d_alloc_pseudo(sock_mnt->mnt_sb, &name);
361	370	if (unlikely(!path.dentry)) {
362	371	put_unused_fd(fd);
...	...	@@ -389,7 +398,7 @@
389	398	int sock_map_fd(struct socket *sock, int flags)
390	399	{
391	400	struct file *newfile;
392		- int fd = sock_alloc_file(sock, &newfile, flags);
	401	+ int fd = sock_alloc_file(sock, &newfile, flags, NULL);
393	402
394	403	if (likely(fd >= 0))
395	404	fd_install(fd, newfile);
...	...	@@ -455,6 +464,68 @@
455	464	return NULL;
456	465	}
457	466
	467	+#define XATTR_SOCKPROTONAME_SUFFIX "sockprotoname"
	468	+#define XATTR_NAME_SOCKPROTONAME (XATTR_SYSTEM_PREFIX XATTR_SOCKPROTONAME_SUFFIX)
	469	+#define XATTR_NAME_SOCKPROTONAME_LEN (sizeof(XATTR_NAME_SOCKPROTONAME)-1)
	470	+static ssize_t sockfs_getxattr(struct dentry *dentry,
	471	+ const char name, void value, size_t size)
	472	+{
	473	+ const char *proto_name;
	474	+ size_t proto_size;
	475	+ int error;
	476	+
	477	+ error = -ENODATA;
	478	+ if (!strncmp(name, XATTR_NAME_SOCKPROTONAME, XATTR_NAME_SOCKPROTONAME_LEN)) {
	479	+ proto_name = dentry->d_name.name;
	480	+ proto_size = strlen(proto_name);
	481	+
	482	+ if (value) {
	483	+ error = -ERANGE;
	484	+ if (proto_size + 1 > size)
	485	+ goto out;
	486	+
	487	+ strncpy(value, proto_name, proto_size + 1);
	488	+ }
	489	+ error = proto_size + 1;
	490	+ }
	491	+
	492	+out:
	493	+ return error;
	494	+}
	495	+
	496	+static ssize_t sockfs_listxattr(struct dentry dentry, char buffer,
	497	+ size_t size)
	498	+{
	499	+ ssize_t len;
	500	+ ssize_t used = 0;
	501	+
	502	+ len = security_inode_listsecurity(dentry->d_inode, buffer, size);
	503	+ if (len < 0)
	504	+ return len;
	505	+ used += len;
	506	+ if (buffer) {
	507	+ if (size < used)
	508	+ return -ERANGE;
	509	+ buffer += len;
	510	+ }
	511	+
	512	+ len = (XATTR_NAME_SOCKPROTONAME_LEN + 1);
	513	+ used += len;
	514	+ if (buffer) {
	515	+ if (size < used)
	516	+ return -ERANGE;
	517	+ memcpy(buffer, XATTR_NAME_SOCKPROTONAME, len);
	518	+ buffer += len;
	519	+ }
	520	+
	521	+ return used;
	522	+}
	523	+
	524	+static const struct inode_operations sockfs_inode_ops = {
	525	+ .getxattr = sockfs_getxattr,
	526	+ .listxattr = sockfs_listxattr,
	527	+};
	528	+
458	529	/**
459	530	* sock_alloc - allocate a socket
460	531	*
...	...	@@ -479,6 +550,7 @@
479	550	inode->i_mode = S_IFSOCK \| S_IRWXUGO;
480	551	inode->i_uid = current_fsuid();
481	552	inode->i_gid = current_fsgid();
	553	+ inode->i_op = &sockfs_inode_ops;
482	554
483	555	this_cpu_add(sockets_in_use, 1);
484	556	return sock;
485	557
...	...	@@ -1394,13 +1466,13 @@
1394	1466	if (err < 0)
1395	1467	goto out_release_both;
1396	1468
1397		- fd1 = sock_alloc_file(sock1, &newfile1, flags);
	1469	+ fd1 = sock_alloc_file(sock1, &newfile1, flags, NULL);
1398	1470	if (unlikely(fd1 < 0)) {
1399	1471	err = fd1;
1400	1472	goto out_release_both;
1401	1473	}
1402	1474
1403		- fd2 = sock_alloc_file(sock2, &newfile2, flags);
	1475	+ fd2 = sock_alloc_file(sock2, &newfile2, flags, NULL);
1404	1476	if (unlikely(fd2 < 0)) {
1405	1477	err = fd2;
1406	1478	fput(newfile1);
...	...	@@ -1536,7 +1608,8 @@
1536	1608	*/
1537	1609	__module_get(newsock->ops->owner);
1538	1610
1539		- newfd = sock_alloc_file(newsock, &newfile, flags);
	1611	+ newfd = sock_alloc_file(newsock, &newfile, flags,
	1612	+ sock->sk->sk_prot_creator->name);
1540	1613	if (unlikely(newfd < 0)) {
1541	1614	err = newfd;
1542	1615	sock_release(newsock);