proc: fix /proc/net/* after setns(2)

/proc entries under /proc/net/* can't be cached into dcache because
setns(2) can change current net namespace.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: avoid vim miscolorization]
[adobriyan@gmail.com: write test, add dummy ->d_revalidate hook: necessary if /proc/net/* is pinned at setns time]
  Link: http://lkml.kernel.org/r/20190108192350.GA12034@avx2
Link: http://lkml.kernel.org/r/20190107162336.GA9239@avx2
Fixes: 1da4d377f9 ("proc: revalidate misc dentries")
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: Mateusz Stępień <mateusz.stepien@netrounds.com>
Reported-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
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 2019-02-01 14:20:01 -08:00 committed by Linus Torvalds
parent 1723058eab
commit 1fde6f21d9
6 changed files with 155 additions and 1 deletions

View File

@ -256,7 +256,7 @@ struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
inode = proc_get_inode(dir->i_sb, de);
if (!inode)
return ERR_PTR(-ENOMEM);
d_set_d_op(dentry, &proc_misc_dentry_ops);
d_set_d_op(dentry, de->proc_dops);
return d_splice_alias(inode, dentry);
}
read_unlock(&proc_subdir_lock);
@ -429,6 +429,8 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
INIT_LIST_HEAD(&ent->pde_openers);
proc_set_user(ent, (*parent)->uid, (*parent)->gid);
ent->proc_dops = &proc_misc_dentry_ops;
out:
return ent;
}

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@ -44,6 +44,7 @@ struct proc_dir_entry {
struct completion *pde_unload_completion;
const struct inode_operations *proc_iops;
const struct file_operations *proc_fops;
const struct dentry_operations *proc_dops;
union {
const struct seq_operations *seq_ops;
int (*single_show)(struct seq_file *, void *);

View File

@ -38,6 +38,22 @@ 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;
@ -90,6 +106,7 @@ struct proc_dir_entry *proc_create_net_data(const char *name, umode_t mode,
p = proc_create_reg(name, mode, &parent, data);
if (!p)
return NULL;
pde_force_lookup(p);
p->proc_fops = &proc_net_seq_fops;
p->seq_ops = ops;
p->state_size = state_size;
@ -133,6 +150,7 @@ struct proc_dir_entry *proc_create_net_data_write(const char *name, umode_t mode
p = proc_create_reg(name, mode, &parent, data);
if (!p)
return NULL;
pde_force_lookup(p);
p->proc_fops = &proc_net_seq_fops;
p->seq_ops = ops;
p->state_size = state_size;
@ -181,6 +199,7 @@ struct proc_dir_entry *proc_create_net_single(const char *name, umode_t mode,
p = proc_create_reg(name, mode, &parent, data);
if (!p)
return NULL;
pde_force_lookup(p);
p->proc_fops = &proc_net_single_fops;
p->single_show = show;
return proc_register(parent, p);
@ -223,6 +242,7 @@ struct proc_dir_entry *proc_create_net_single_write(const char *name, umode_t mo
p = proc_create_reg(name, mode, &parent, data);
if (!p)
return NULL;
pde_force_lookup(p);
p->proc_fops = &proc_net_single_fops;
p->single_show = show;
p->write = write;

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@ -10,4 +10,5 @@
/proc-uptime-002
/read
/self
/setns-dcache
/thread-self

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@ -14,6 +14,7 @@ TEST_GEN_PROGS += proc-uptime-001
TEST_GEN_PROGS += proc-uptime-002
TEST_GEN_PROGS += read
TEST_GEN_PROGS += self
TEST_GEN_PROGS += setns-dcache
TEST_GEN_PROGS += thread-self
include ../lib.mk

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@ -0,0 +1,129 @@
/*
* Copyright © 2019 Alexey Dobriyan <adobriyan@gmail.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* Test that setns(CLONE_NEWNET) points to new /proc/net content even
* if old one is in dcache.
*
* FIXME /proc/net/unix is under CONFIG_UNIX which can be disabled.
*/
#undef NDEBUG
#include <assert.h>
#include <errno.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
static pid_t pid = -1;
static void f(void)
{
if (pid > 0) {
kill(pid, SIGTERM);
}
}
int main(void)
{
int fd[2];
char _ = 0;
int nsfd;
atexit(f);
/* Check for priviledges and syscall availability straight away. */
if (unshare(CLONE_NEWNET) == -1) {
if (errno == ENOSYS || errno == EPERM) {
return 4;
}
return 1;
}
/* Distinguisher between two otherwise empty net namespaces. */
if (socket(AF_UNIX, SOCK_STREAM, 0) == -1) {
return 1;
}
if (pipe(fd) == -1) {
return 1;
}
pid = fork();
if (pid == -1) {
return 1;
}
if (pid == 0) {
if (unshare(CLONE_NEWNET) == -1) {
return 1;
}
if (write(fd[1], &_, 1) != 1) {
return 1;
}
pause();
return 0;
}
if (read(fd[0], &_, 1) != 1) {
return 1;
}
{
char buf[64];
snprintf(buf, sizeof(buf), "/proc/%u/ns/net", pid);
nsfd = open(buf, O_RDONLY);
if (nsfd == -1) {
return 1;
}
}
/* Reliably pin dentry into dcache. */
(void)open("/proc/net/unix", O_RDONLY);
if (setns(nsfd, CLONE_NEWNET) == -1) {
return 1;
}
kill(pid, SIGTERM);
pid = 0;
{
char buf[4096];
ssize_t rv;
int fd;
fd = open("/proc/net/unix", O_RDONLY);
if (fd == -1) {
return 1;
}
#define S "Num RefCount Protocol Flags Type St Inode Path\n"
rv = read(fd, buf, sizeof(buf));
assert(rv == strlen(S));
assert(memcmp(buf, S, strlen(S)) == 0);
}
return 0;
}