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

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Commit 1fde6f21d9 ("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: 1da4d377f9 ("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>
This commit is contained in:
Alexey Dobriyan 2020-12-15 20:42:39 -08:00 committed by Linus Torvalds
parent fe71988834
commit c6c75deda8
4 changed files with 36 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
fs/proc/generic.c
View File

@ -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,

7
fs/proc/internal.h
View File

@ -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;
}

16
fs/proc/proc_net.c
View File

@ -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;

8
include/linux/proc_fs.h
View File

@ -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;