proc: fix lookup in /proc/net subdirectories after setns(2)

Commit 1fde6f21d90f ("proc: fix /proc/net/* after setns(2)") only forced
revalidation of regular files under /proc/net/

However, /proc/net/ is unusual in the sense of /proc/net/foo handlers
take netns pointer from parent directory which is old netns.

Steps to reproduce:

	(void)open("/proc/net/sctp/snmp", O_RDONLY);
	unshare(CLONE_NEWNET);

	int fd = open("/proc/net/sctp/snmp", O_RDONLY);
	read(fd, &c, 1);

Read will read wrong data from original netns.

Patch forces lookup on every directory under /proc/net .

Link: https://lkml.kernel.org/r/20201205160916.GA109739@localhost.localdomain
Fixes: 1da4d377f943 ("proc: revalidate misc dentries")
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: "Rantala, Tommi T. (Nokia - FI/Espoo)" <tommi.t.rantala@nokia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index b84663252adda0abadc9656bb56e441f4f65d570..6c0a05f55d6b12b4551bfd9e5879d01f50209a0e 100644 (file)
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -349,6 +349,16 @@ static const struct file_operations proc_dir_operations = {
        .iterate_shared         = proc_readdir,
 };
 
+static int proc_net_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+       return 0;
+}
+
+const struct dentry_operations proc_net_dentry_ops = {
+       .d_revalidate   = proc_net_d_revalidate,
+       .d_delete       = always_delete_dentry,
+};
+
 /*
  * proc directories can do almost nothing..
  */
@@ -471,8 +481,8 @@ struct proc_dir_entry *proc_symlink(const char *name,
 }
 EXPORT_SYMBOL(proc_symlink);
 
-struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
-               struct proc_dir_entry *parent, void *data)
+struct proc_dir_entry *_proc_mkdir(const char *name, umode_t mode,
+               struct proc_dir_entry *parent, void *data, bool force_lookup)
 {
        struct proc_dir_entry *ent;
 
@@ -484,10 +494,20 @@ struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
                ent->data = data;
                ent->proc_dir_ops = &proc_dir_operations;
                ent->proc_iops = &proc_dir_inode_operations;
+               if (force_lookup) {
+                       pde_force_lookup(ent);
+               }
                ent = proc_register(parent, ent);
        }
        return ent;
 }
+EXPORT_SYMBOL_GPL(_proc_mkdir);
+
+struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
+               struct proc_dir_entry *parent, void *data)
+{
+       return _proc_mkdir(name, mode, parent, data, false);
+}
 EXPORT_SYMBOL_GPL(proc_mkdir_data);
 
 struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 917cc85e346630c11190085ce8ff191439dfb7dd..afbe96b6bf77def7e5cd5b3d62e90b20c87728b4 100644 (file)
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -310,3 +310,10 @@ extern unsigned long task_statm(struct mm_struct *,
                                unsigned long *, unsigned long *,
                                unsigned long *, unsigned long *);
 extern void task_mem(struct seq_file *, struct mm_struct *);
+
+extern const struct dentry_operations proc_net_dentry_ops;
+static inline void pde_force_lookup(struct proc_dir_entry *pde)
+{
+       /* /proc/net/ entries can be changed under us by setns(CLONE_NEWNET) */
+       pde->proc_dops = &proc_net_dentry_ops;
+}

diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 45c7318a2ce50616fe7adf0c92be7e1b8eef7546..18601042af998882f656ab7968efcd0bd85ed912 100644 (file)
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -39,22 +39,6 @@ static struct net *get_proc_net(const struct inode *inode)
        return maybe_get_net(PDE_NET(PDE(inode)));
 }
 
-static int proc_net_d_revalidate(struct dentry *dentry, unsigned int flags)
-{
-       return 0;
-}
-
-static const struct dentry_operations proc_net_dentry_ops = {
-       .d_revalidate   = proc_net_d_revalidate,
-       .d_delete       = always_delete_dentry,
-};
-
-static void pde_force_lookup(struct proc_dir_entry *pde)
-{
-       /* /proc/net/ entries can be changed under us by setns(CLONE_NEWNET) */
-       pde->proc_dops = &proc_net_dentry_ops;
-}
-
 static int seq_open_net(struct inode *inode, struct file *file)
 {
        unsigned int state_size = PDE(inode)->state_size;

diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 270cab43ca3dadc92db669c403558d321630faeb..000cc0533c3366abe4bea0acb9f0e700381706c8 100644 (file)
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -80,6 +80,7 @@ extern void proc_flush_pid(struct pid *);
 
 extern struct proc_dir_entry *proc_symlink(const char *,
                struct proc_dir_entry *, const char *);
+struct proc_dir_entry *_proc_mkdir(const char *, umode_t, struct proc_dir_entry *, void *, bool);
 extern struct proc_dir_entry *proc_mkdir(const char *, struct proc_dir_entry *);
 extern struct proc_dir_entry *proc_mkdir_data(const char *, umode_t,
                                              struct proc_dir_entry *, void *);
@@ -162,6 +163,11 @@ static inline struct proc_dir_entry *proc_symlink(const char *name,
 static inline struct proc_dir_entry *proc_mkdir(const char *name,
        struct proc_dir_entry *parent) {return NULL;}
 static inline struct proc_dir_entry *proc_create_mount_point(const char *name) { return NULL; }
+static inline struct proc_dir_entry *_proc_mkdir(const char *name, umode_t mode,
+               struct proc_dir_entry *parent, void *data, bool force_lookup)
+{
+       return NULL;
+}
 static inline struct proc_dir_entry *proc_mkdir_data(const char *name,
        umode_t mode, struct proc_dir_entry *parent, void *data) { return NULL; }
 static inline struct proc_dir_entry *proc_mkdir_mode(const char *name,
@@ -199,7 +205,7 @@ struct net;
 static inline struct proc_dir_entry *proc_net_mkdir(
        struct net *net, const char *name, struct proc_dir_entry *parent)
 {
-       return proc_mkdir_data(name, 0, parent, net);
+       return _proc_mkdir(name, 0, parent, net, true);
 }
 
 struct ns_common;