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9f35a33b8d
Fix a NULL pointer deref in the user-defined key type whereby updating a negative key into a fully instantiated key will cause an oops to occur when the code attempts to free the non-existent old payload. This results in an oops that looks something like the following: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: [<ffffffff81085fa1>] __call_rcu+0x11/0x13e PGD 3391d067 PUD 3894a067 PMD 0 Oops: 0002 [#1] SMP CPU 1 Pid: 4354, comm: keyctl Not tainted 3.1.0-fsdevel+ #1140 /DG965RY RIP: 0010:[<ffffffff81085fa1>] [<ffffffff81085fa1>] __call_rcu+0x11/0x13e RSP: 0018:ffff88003d591df8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000000006e RDX: ffffffff8161d0c0 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff88003d591e18 R08: 0000000000000000 R09: ffffffff8152fa6c R10: 0000000000000000 R11: 0000000000000300 R12: ffff88003b8f9538 R13: ffffffff8161d0c0 R14: ffff88003b8f9d50 R15: ffff88003c69f908 FS: 00007f97eb18c720(0000) GS:ffff88003bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000008 CR3: 000000003d47a000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process keyctl (pid: 4354, threadinfo ffff88003d590000, task ffff88003c78a040) Stack: ffff88003e0ffde0 ffff88003b8f9538 0000000000000001 ffff88003b8f9d50 ffff88003d591e28 ffffffff810860f0 ffff88003d591e68 ffffffff8117bfea ffff88003d591e68 ffffffff00000000 ffff88003e0ffde1 ffff88003e0ffde0 Call Trace: [<ffffffff810860f0>] call_rcu_sched+0x10/0x12 [<ffffffff8117bfea>] user_update+0x8d/0xa2 [<ffffffff8117723a>] key_create_or_update+0x236/0x270 [<ffffffff811789b1>] sys_add_key+0x123/0x17e [<ffffffff813b84bb>] system_call_fastpath+0x16/0x1b Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Jeff Layton <jlayton@redhat.com> Acked-by: Neil Horman <nhorman@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: James Morris <jmorris@namei.org> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
192 lines
3.9 KiB
C
192 lines
3.9 KiB
C
/* user_defined.c: user defined key type
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/seq_file.h>
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#include <linux/err.h>
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#include <keys/user-type.h>
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#include <asm/uaccess.h>
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#include "internal.h"
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/*
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* user defined keys take an arbitrary string as the description and an
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* arbitrary blob of data as the payload
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*/
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struct key_type key_type_user = {
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.name = "user",
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.instantiate = user_instantiate,
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.update = user_update,
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.match = user_match,
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.revoke = user_revoke,
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.destroy = user_destroy,
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.describe = user_describe,
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.read = user_read,
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};
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EXPORT_SYMBOL_GPL(key_type_user);
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/*
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* instantiate a user defined key
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*/
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int user_instantiate(struct key *key, const void *data, size_t datalen)
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{
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struct user_key_payload *upayload;
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int ret;
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ret = -EINVAL;
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if (datalen <= 0 || datalen > 32767 || !data)
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goto error;
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ret = key_payload_reserve(key, datalen);
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if (ret < 0)
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goto error;
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ret = -ENOMEM;
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upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
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if (!upayload)
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goto error;
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/* attach the data */
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upayload->datalen = datalen;
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memcpy(upayload->data, data, datalen);
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rcu_assign_pointer(key->payload.data, upayload);
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ret = 0;
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error:
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return ret;
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}
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EXPORT_SYMBOL_GPL(user_instantiate);
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/*
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* update a user defined key
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* - the key's semaphore is write-locked
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*/
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int user_update(struct key *key, const void *data, size_t datalen)
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{
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struct user_key_payload *upayload, *zap;
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int ret;
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ret = -EINVAL;
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if (datalen <= 0 || datalen > 32767 || !data)
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goto error;
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/* construct a replacement payload */
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ret = -ENOMEM;
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upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
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if (!upayload)
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goto error;
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upayload->datalen = datalen;
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memcpy(upayload->data, data, datalen);
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/* check the quota and attach the new data */
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zap = upayload;
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ret = key_payload_reserve(key, datalen);
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if (ret == 0) {
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/* attach the new data, displacing the old */
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zap = key->payload.data;
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rcu_assign_pointer(key->payload.data, upayload);
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key->expiry = 0;
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}
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if (zap)
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kfree_rcu(zap, rcu);
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error:
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return ret;
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}
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EXPORT_SYMBOL_GPL(user_update);
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/*
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* match users on their name
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*/
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int user_match(const struct key *key, const void *description)
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{
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return strcmp(key->description, description) == 0;
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}
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EXPORT_SYMBOL_GPL(user_match);
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/*
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* dispose of the links from a revoked keyring
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* - called with the key sem write-locked
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*/
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void user_revoke(struct key *key)
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{
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struct user_key_payload *upayload = key->payload.data;
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/* clear the quota */
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key_payload_reserve(key, 0);
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if (upayload) {
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rcu_assign_pointer(key->payload.data, NULL);
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kfree_rcu(upayload, rcu);
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}
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}
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EXPORT_SYMBOL(user_revoke);
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/*
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* dispose of the data dangling from the corpse of a user key
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*/
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void user_destroy(struct key *key)
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{
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struct user_key_payload *upayload = key->payload.data;
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kfree(upayload);
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}
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EXPORT_SYMBOL_GPL(user_destroy);
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/*
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* describe the user key
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*/
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void user_describe(const struct key *key, struct seq_file *m)
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{
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seq_puts(m, key->description);
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if (key_is_instantiated(key))
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seq_printf(m, ": %u", key->datalen);
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}
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EXPORT_SYMBOL_GPL(user_describe);
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/*
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* read the key data
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* - the key's semaphore is read-locked
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*/
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long user_read(const struct key *key, char __user *buffer, size_t buflen)
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{
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struct user_key_payload *upayload;
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long ret;
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upayload = rcu_dereference_key(key);
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ret = upayload->datalen;
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/* we can return the data as is */
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if (buffer && buflen > 0) {
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if (buflen > upayload->datalen)
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buflen = upayload->datalen;
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if (copy_to_user(buffer, upayload->data, buflen) != 0)
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ret = -EFAULT;
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}
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return ret;
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}
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EXPORT_SYMBOL_GPL(user_read);
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