linux/security/keys/proc.c
Vasily Averin 86d32f9a7c keys: Fix proc_keys_next to increase position index
If seq_file .next function does not change position index,
read after some lseek can generate unexpected output:

    $ dd if=/proc/keys bs=1  # full usual output
    0f6bfdf5 I--Q---     2 perm 3f010000  1000  1000 user      4af2f79ab8848d0a: 740
    1fb91b32 I--Q---     3 perm 1f3f0000  1000 65534 keyring   _uid.1000: 2
    27589480 I--Q---     1 perm 0b0b0000     0     0 user      invocation_id: 16
    2f33ab67 I--Q---   152 perm 3f030000     0     0 keyring   _ses: 2
    33f1d8fa I--Q---     4 perm 3f030000  1000  1000 keyring   _ses: 1
    3d427fda I--Q---     2 perm 3f010000  1000  1000 user      69ec44aec7678e5a: 740
    3ead4096 I--Q---     1 perm 1f3f0000  1000 65534 keyring   _uid_ses.1000: 1
    521+0 records in
    521+0 records out
    521 bytes copied, 0,00123769 s, 421 kB/s

But a read after lseek in middle of last line results in the partial
last line and then a repeat of the final line:

    $ dd if=/proc/keys bs=500 skip=1
    dd: /proc/keys: cannot skip to specified offset
    g   _uid_ses.1000: 1
    3ead4096 I--Q---     1 perm 1f3f0000  1000 65534 keyring   _uid_ses.1000: 1
    0+1 records in
    0+1 records out
    97 bytes copied, 0,000135035 s, 718 kB/s

and a read after lseek beyond end of file results in the last line being
shown:

    $ dd if=/proc/keys bs=1000 skip=1   # read after lseek beyond end of file
    dd: /proc/keys: cannot skip to specified offset
    3ead4096 I--Q---     1 perm 1f3f0000  1000 65534 keyring   _uid_ses.1000: 1
    0+1 records in
    0+1 records out
    76 bytes copied, 0,000119981 s, 633 kB/s

See https://bugzilla.kernel.org/show_bug.cgi?id=206283

Fixes: 1f4aace60b ("fs/seq_file.c: simplify seq_file iteration code ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-16 10:10:50 -07:00

324 lines
7.7 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* procfs files for key database enumeration
*
* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <asm/errno.h>
#include "internal.h"
static void *proc_keys_start(struct seq_file *p, loff_t *_pos);
static void *proc_keys_next(struct seq_file *p, void *v, loff_t *_pos);
static void proc_keys_stop(struct seq_file *p, void *v);
static int proc_keys_show(struct seq_file *m, void *v);
static const struct seq_operations proc_keys_ops = {
.start = proc_keys_start,
.next = proc_keys_next,
.stop = proc_keys_stop,
.show = proc_keys_show,
};
static void *proc_key_users_start(struct seq_file *p, loff_t *_pos);
static void *proc_key_users_next(struct seq_file *p, void *v, loff_t *_pos);
static void proc_key_users_stop(struct seq_file *p, void *v);
static int proc_key_users_show(struct seq_file *m, void *v);
static const struct seq_operations proc_key_users_ops = {
.start = proc_key_users_start,
.next = proc_key_users_next,
.stop = proc_key_users_stop,
.show = proc_key_users_show,
};
/*
* Declare the /proc files.
*/
static int __init key_proc_init(void)
{
struct proc_dir_entry *p;
p = proc_create_seq("keys", 0, NULL, &proc_keys_ops);
if (!p)
panic("Cannot create /proc/keys\n");
p = proc_create_seq("key-users", 0, NULL, &proc_key_users_ops);
if (!p)
panic("Cannot create /proc/key-users\n");
return 0;
}
__initcall(key_proc_init);
/*
* Implement "/proc/keys" to provide a list of the keys on the system that
* grant View permission to the caller.
*/
static struct rb_node *key_serial_next(struct seq_file *p, struct rb_node *n)
{
struct user_namespace *user_ns = seq_user_ns(p);
n = rb_next(n);
while (n) {
struct key *key = rb_entry(n, struct key, serial_node);
if (kuid_has_mapping(user_ns, key->user->uid))
break;
n = rb_next(n);
}
return n;
}
static struct key *find_ge_key(struct seq_file *p, key_serial_t id)
{
struct user_namespace *user_ns = seq_user_ns(p);
struct rb_node *n = key_serial_tree.rb_node;
struct key *minkey = NULL;
while (n) {
struct key *key = rb_entry(n, struct key, serial_node);
if (id < key->serial) {
if (!minkey || minkey->serial > key->serial)
minkey = key;
n = n->rb_left;
} else if (id > key->serial) {
n = n->rb_right;
} else {
minkey = key;
break;
}
key = NULL;
}
if (!minkey)
return NULL;
for (;;) {
if (kuid_has_mapping(user_ns, minkey->user->uid))
return minkey;
n = rb_next(&minkey->serial_node);
if (!n)
return NULL;
minkey = rb_entry(n, struct key, serial_node);
}
}
static void *proc_keys_start(struct seq_file *p, loff_t *_pos)
__acquires(key_serial_lock)
{
key_serial_t pos = *_pos;
struct key *key;
spin_lock(&key_serial_lock);
if (*_pos > INT_MAX)
return NULL;
key = find_ge_key(p, pos);
if (!key)
return NULL;
*_pos = key->serial;
return &key->serial_node;
}
static inline key_serial_t key_node_serial(struct rb_node *n)
{
struct key *key = rb_entry(n, struct key, serial_node);
return key->serial;
}
static void *proc_keys_next(struct seq_file *p, void *v, loff_t *_pos)
{
struct rb_node *n;
n = key_serial_next(p, v);
if (n)
*_pos = key_node_serial(n);
else
(*_pos)++;
return n;
}
static void proc_keys_stop(struct seq_file *p, void *v)
__releases(key_serial_lock)
{
spin_unlock(&key_serial_lock);
}
static int proc_keys_show(struct seq_file *m, void *v)
{
struct rb_node *_p = v;
struct key *key = rb_entry(_p, struct key, serial_node);
unsigned long flags;
key_ref_t key_ref, skey_ref;
time64_t now, expiry;
char xbuf[16];
short state;
u64 timo;
int rc;
struct keyring_search_context ctx = {
.index_key = key->index_key,
.cred = m->file->f_cred,
.match_data.cmp = lookup_user_key_possessed,
.match_data.raw_data = key,
.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
.flags = (KEYRING_SEARCH_NO_STATE_CHECK |
KEYRING_SEARCH_RECURSE),
};
key_ref = make_key_ref(key, 0);
/* determine if the key is possessed by this process (a test we can
* skip if the key does not indicate the possessor can view it
*/
if (key->perm & KEY_POS_VIEW) {
rcu_read_lock();
skey_ref = search_cred_keyrings_rcu(&ctx);
rcu_read_unlock();
if (!IS_ERR(skey_ref)) {
key_ref_put(skey_ref);
key_ref = make_key_ref(key, 1);
}
}
/* check whether the current task is allowed to view the key */
rc = key_task_permission(key_ref, ctx.cred, KEY_NEED_VIEW);
if (rc < 0)
return 0;
now = ktime_get_real_seconds();
rcu_read_lock();
/* come up with a suitable timeout value */
expiry = READ_ONCE(key->expiry);
if (expiry == 0) {
memcpy(xbuf, "perm", 5);
} else if (now >= expiry) {
memcpy(xbuf, "expd", 5);
} else {
timo = expiry - now;
if (timo < 60)
sprintf(xbuf, "%llus", timo);
else if (timo < 60*60)
sprintf(xbuf, "%llum", div_u64(timo, 60));
else if (timo < 60*60*24)
sprintf(xbuf, "%lluh", div_u64(timo, 60 * 60));
else if (timo < 60*60*24*7)
sprintf(xbuf, "%llud", div_u64(timo, 60 * 60 * 24));
else
sprintf(xbuf, "%lluw", div_u64(timo, 60 * 60 * 24 * 7));
}
state = key_read_state(key);
#define showflag(FLAGS, LETTER, FLAG) \
((FLAGS & (1 << FLAG)) ? LETTER : '-')
flags = READ_ONCE(key->flags);
seq_printf(m, "%08x %c%c%c%c%c%c%c %5d %4s %08x %5d %5d %-9.9s ",
key->serial,
state != KEY_IS_UNINSTANTIATED ? 'I' : '-',
showflag(flags, 'R', KEY_FLAG_REVOKED),
showflag(flags, 'D', KEY_FLAG_DEAD),
showflag(flags, 'Q', KEY_FLAG_IN_QUOTA),
showflag(flags, 'U', KEY_FLAG_USER_CONSTRUCT),
state < 0 ? 'N' : '-',
showflag(flags, 'i', KEY_FLAG_INVALIDATED),
refcount_read(&key->usage),
xbuf,
key->perm,
from_kuid_munged(seq_user_ns(m), key->uid),
from_kgid_munged(seq_user_ns(m), key->gid),
key->type->name);
#undef showflag
if (key->type->describe)
key->type->describe(key, m);
seq_putc(m, '\n');
rcu_read_unlock();
return 0;
}
static struct rb_node *__key_user_next(struct user_namespace *user_ns, struct rb_node *n)
{
while (n) {
struct key_user *user = rb_entry(n, struct key_user, node);
if (kuid_has_mapping(user_ns, user->uid))
break;
n = rb_next(n);
}
return n;
}
static struct rb_node *key_user_next(struct user_namespace *user_ns, struct rb_node *n)
{
return __key_user_next(user_ns, rb_next(n));
}
static struct rb_node *key_user_first(struct user_namespace *user_ns, struct rb_root *r)
{
struct rb_node *n = rb_first(r);
return __key_user_next(user_ns, n);
}
static void *proc_key_users_start(struct seq_file *p, loff_t *_pos)
__acquires(key_user_lock)
{
struct rb_node *_p;
loff_t pos = *_pos;
spin_lock(&key_user_lock);
_p = key_user_first(seq_user_ns(p), &key_user_tree);
while (pos > 0 && _p) {
pos--;
_p = key_user_next(seq_user_ns(p), _p);
}
return _p;
}
static void *proc_key_users_next(struct seq_file *p, void *v, loff_t *_pos)
{
(*_pos)++;
return key_user_next(seq_user_ns(p), (struct rb_node *)v);
}
static void proc_key_users_stop(struct seq_file *p, void *v)
__releases(key_user_lock)
{
spin_unlock(&key_user_lock);
}
static int proc_key_users_show(struct seq_file *m, void *v)
{
struct rb_node *_p = v;
struct key_user *user = rb_entry(_p, struct key_user, node);
unsigned maxkeys = uid_eq(user->uid, GLOBAL_ROOT_UID) ?
key_quota_root_maxkeys : key_quota_maxkeys;
unsigned maxbytes = uid_eq(user->uid, GLOBAL_ROOT_UID) ?
key_quota_root_maxbytes : key_quota_maxbytes;
seq_printf(m, "%5u: %5d %d/%d %d/%d %d/%d\n",
from_kuid_munged(seq_user_ns(m), user->uid),
refcount_read(&user->usage),
atomic_read(&user->nkeys),
atomic_read(&user->nikeys),
user->qnkeys,
maxkeys,
user->qnbytes,
maxbytes);
return 0;
}