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

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[ Upstream commit c6c75deda81344c3a95d1d1f606d5cee109e5d54 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alexey Dobriyan
2020-12-15 20:42:39 -08:00
committed by Greg Kroah-Hartman
parent bd3f4b6fd9
commit b202ac9c73
4 changed files with 36 additions and 19 deletions
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8
include/linux/proc_fs.h
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@@ -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;