From: Waiman Long longman@redhat.com
commit d3ec10aa95819bff18a0d936b18884c7816d0914 upstream.
A lockdep circular locking dependency report was seen when running a keyutils test:
[12537.027242] ====================================================== [12537.059309] WARNING: possible circular locking dependency detected [12537.088148] 4.18.0-147.7.1.el8_1.x86_64+debug #1 Tainted: G OE --------- - - [12537.125253] ------------------------------------------------------ [12537.153189] keyctl/25598 is trying to acquire lock: [12537.175087] 000000007c39f96c (&mm->mmap_sem){++++}, at: __might_fault+0xc4/0x1b0 [12537.208365] [12537.208365] but task is already holding lock: [12537.234507] 000000003de5b58d (&type->lock_class){++++}, at: keyctl_read_key+0x15a/0x220 [12537.270476] [12537.270476] which lock already depends on the new lock. [12537.270476] [12537.307209] [12537.307209] the existing dependency chain (in reverse order) is: [12537.340754] [12537.340754] -> #3 (&type->lock_class){++++}: [12537.367434] down_write+0x4d/0x110 [12537.385202] __key_link_begin+0x87/0x280 [12537.405232] request_key_and_link+0x483/0xf70 [12537.427221] request_key+0x3c/0x80 [12537.444839] dns_query+0x1db/0x5a5 [dns_resolver] [12537.468445] dns_resolve_server_name_to_ip+0x1e1/0x4d0 [cifs] [12537.496731] cifs_reconnect+0xe04/0x2500 [cifs] [12537.519418] cifs_readv_from_socket+0x461/0x690 [cifs] [12537.546263] cifs_read_from_socket+0xa0/0xe0 [cifs] [12537.573551] cifs_demultiplex_thread+0x311/0x2db0 [cifs] [12537.601045] kthread+0x30c/0x3d0 [12537.617906] ret_from_fork+0x3a/0x50 [12537.636225] [12537.636225] -> #2 (root_key_user.cons_lock){+.+.}: [12537.664525] __mutex_lock+0x105/0x11f0 [12537.683734] request_key_and_link+0x35a/0xf70 [12537.705640] request_key+0x3c/0x80 [12537.723304] dns_query+0x1db/0x5a5 [dns_resolver] [12537.746773] dns_resolve_server_name_to_ip+0x1e1/0x4d0 [cifs] [12537.775607] cifs_reconnect+0xe04/0x2500 [cifs] [12537.798322] cifs_readv_from_socket+0x461/0x690 [cifs] [12537.823369] cifs_read_from_socket+0xa0/0xe0 [cifs] [12537.847262] cifs_demultiplex_thread+0x311/0x2db0 [cifs] [12537.873477] kthread+0x30c/0x3d0 [12537.890281] ret_from_fork+0x3a/0x50 [12537.908649] [12537.908649] -> #1 (&tcp_ses->srv_mutex){+.+.}: [12537.935225] __mutex_lock+0x105/0x11f0 [12537.954450] cifs_call_async+0x102/0x7f0 [cifs] [12537.977250] smb2_async_readv+0x6c3/0xc90 [cifs] [12538.000659] cifs_readpages+0x120a/0x1e50 [cifs] [12538.023920] read_pages+0xf5/0x560 [12538.041583] __do_page_cache_readahead+0x41d/0x4b0 [12538.067047] ondemand_readahead+0x44c/0xc10 [12538.092069] filemap_fault+0xec1/0x1830 [12538.111637] __do_fault+0x82/0x260 [12538.129216] do_fault+0x419/0xfb0 [12538.146390] __handle_mm_fault+0x862/0xdf0 [12538.167408] handle_mm_fault+0x154/0x550 [12538.187401] __do_page_fault+0x42f/0xa60 [12538.207395] do_page_fault+0x38/0x5e0 [12538.225777] page_fault+0x1e/0x30 [12538.243010] [12538.243010] -> #0 (&mm->mmap_sem){++++}: [12538.267875] lock_acquire+0x14c/0x420 [12538.286848] __might_fault+0x119/0x1b0 [12538.306006] keyring_read_iterator+0x7e/0x170 [12538.327936] assoc_array_subtree_iterate+0x97/0x280 [12538.352154] keyring_read+0xe9/0x110 [12538.370558] keyctl_read_key+0x1b9/0x220 [12538.391470] do_syscall_64+0xa5/0x4b0 [12538.410511] entry_SYSCALL_64_after_hwframe+0x6a/0xdf [12538.435535] [12538.435535] other info that might help us debug this: [12538.435535] [12538.472829] Chain exists of: [12538.472829] &mm->mmap_sem --> root_key_user.cons_lock --> &type->lock_class [12538.472829] [12538.524820] Possible unsafe locking scenario: [12538.524820] [12538.551431] CPU0 CPU1 [12538.572654] ---- ---- [12538.595865] lock(&type->lock_class); [12538.613737] lock(root_key_user.cons_lock); [12538.644234] lock(&type->lock_class); [12538.672410] lock(&mm->mmap_sem); [12538.687758] [12538.687758] *** DEADLOCK *** [12538.687758] [12538.714455] 1 lock held by keyctl/25598: [12538.732097] #0: 000000003de5b58d (&type->lock_class){++++}, at: keyctl_read_key+0x15a/0x220 [12538.770573] [12538.770573] stack backtrace: [12538.790136] CPU: 2 PID: 25598 Comm: keyctl Kdump: loaded Tainted: G [12538.844855] Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 Gen9, BIOS P89 12/27/2015 [12538.881963] Call Trace: [12538.892897] dump_stack+0x9a/0xf0 [12538.907908] print_circular_bug.isra.25.cold.50+0x1bc/0x279 [12538.932891] ? save_trace+0xd6/0x250 [12538.948979] check_prev_add.constprop.32+0xc36/0x14f0 [12538.971643] ? keyring_compare_object+0x104/0x190 [12538.992738] ? check_usage+0x550/0x550 [12539.009845] ? sched_clock+0x5/0x10 [12539.025484] ? sched_clock_cpu+0x18/0x1e0 [12539.043555] __lock_acquire+0x1f12/0x38d0 [12539.061551] ? trace_hardirqs_on+0x10/0x10 [12539.080554] lock_acquire+0x14c/0x420 [12539.100330] ? __might_fault+0xc4/0x1b0 [12539.119079] __might_fault+0x119/0x1b0 [12539.135869] ? __might_fault+0xc4/0x1b0 [12539.153234] keyring_read_iterator+0x7e/0x170 [12539.172787] ? keyring_read+0x110/0x110 [12539.190059] assoc_array_subtree_iterate+0x97/0x280 [12539.211526] keyring_read+0xe9/0x110 [12539.227561] ? keyring_gc_check_iterator+0xc0/0xc0 [12539.249076] keyctl_read_key+0x1b9/0x220 [12539.266660] do_syscall_64+0xa5/0x4b0 [12539.283091] entry_SYSCALL_64_after_hwframe+0x6a/0xdf
One way to prevent this deadlock scenario from happening is to not allow writing to userspace while holding the key semaphore. Instead, an internal buffer is allocated for getting the keys out from the read method first before copying them out to userspace without holding the lock.
That requires taking out the __user modifier from all the relevant read methods as well as additional changes to not use any userspace write helpers. That is,
1) The put_user() call is replaced by a direct copy. 2) The copy_to_user() call is replaced by memcpy(). 3) All the fault handling code is removed.
Compiling on a x86-64 system, the size of the rxrpc_read() function is reduced from 3795 bytes to 2384 bytes with this patch.
Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2") Reviewed-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com Signed-off-by: Waiman Long longman@redhat.com Signed-off-by: David Howells dhowells@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/keys/big_key-type.h | 2 +- include/keys/user-type.h | 3 +- include/linux/key-type.h | 2 +- net/dns_resolver/dns_key.c | 2 +- net/rxrpc/key.c | 27 ++++-------- security/keys/big_key.c | 11 ++--- security/keys/encrypted-keys/encrypted.c | 7 ++- security/keys/keyctl.c | 73 +++++++++++++++++++++++++------- security/keys/keyring.c | 6 +-- security/keys/request_key_auth.c | 7 ++- security/keys/trusted.c | 14 +----- security/keys/user_defined.c | 5 +-- 12 files changed, 85 insertions(+), 74 deletions(-)
diff --git a/include/keys/big_key-type.h b/include/keys/big_key-type.h index e0970a5..a7207a9 100644 --- a/include/keys/big_key-type.h +++ b/include/keys/big_key-type.h @@ -21,6 +21,6 @@ extern void big_key_revoke(struct key *key); extern void big_key_destroy(struct key *key); extern void big_key_describe(const struct key *big_key, struct seq_file *m); -extern long big_key_read(const struct key *key, char __user *buffer, size_t buflen); +extern long big_key_read(const struct key *key, char *buffer, size_t buflen);
#endif /* _KEYS_BIG_KEY_TYPE_H */ diff --git a/include/keys/user-type.h b/include/keys/user-type.h index 12babe9..0d8f3cd 100644 --- a/include/keys/user-type.h +++ b/include/keys/user-type.h @@ -45,8 +45,7 @@ struct user_key_payload { extern void user_revoke(struct key *key); extern void user_destroy(struct key *key); extern void user_describe(const struct key *user, struct seq_file *m); -extern long user_read(const struct key *key, - char __user *buffer, size_t buflen); +extern long user_read(const struct key *key, char *buffer, size_t buflen);
static inline const struct user_key_payload *user_key_payload_rcu(const struct key *key) { diff --git a/include/linux/key-type.h b/include/linux/key-type.h index d3c5ae8..3341dda 100644 --- a/include/linux/key-type.h +++ b/include/linux/key-type.h @@ -125,7 +125,7 @@ struct key_type { * much is copied into the buffer * - shouldn't do the copy if the buffer is NULL */ - long (*read)(const struct key *key, char __user *buffer, size_t buflen); + long (*read)(const struct key *key, char *buffer, size_t buflen);
/* handle request_key() for this type instead of invoking * /sbin/request-key (optional) diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c index 7f45348..a049420 100644 --- a/net/dns_resolver/dns_key.c +++ b/net/dns_resolver/dns_key.c @@ -241,7 +241,7 @@ static void dns_resolver_describe(const struct key *key, struct seq_file *m) * - the key's semaphore is read-locked */ static long dns_resolver_read(const struct key *key, - char __user *buffer, size_t buflen) + char *buffer, size_t buflen) { int err = PTR_ERR(key->payload.data[dns_key_error]);
diff --git a/net/rxrpc/key.c b/net/rxrpc/key.c index e7f6b88..ad9d1b2 100644 --- a/net/rxrpc/key.c +++ b/net/rxrpc/key.c @@ -35,7 +35,7 @@ static void rxrpc_destroy(struct key *); static void rxrpc_destroy_s(struct key *); static void rxrpc_describe(const struct key *, struct seq_file *); -static long rxrpc_read(const struct key *, char __user *, size_t); +static long rxrpc_read(const struct key *, char *, size_t);
/* * rxrpc defined keys take an arbitrary string as the description and an @@ -1044,12 +1044,12 @@ struct key *rxrpc_get_null_key(const char *keyname) * - this returns the result in XDR form */ static long rxrpc_read(const struct key *key, - char __user *buffer, size_t buflen) + char *buffer, size_t buflen) { const struct rxrpc_key_token *token; const struct krb5_principal *princ; size_t size; - __be32 __user *xdr, *oldxdr; + __be32 *xdr, *oldxdr; u32 cnlen, toksize, ntoks, tok, zero; u16 toksizes[AFSTOKEN_MAX]; int loop; @@ -1126,30 +1126,25 @@ static long rxrpc_read(const struct key *key, if (!buffer || buflen < size) return size;
- xdr = (__be32 __user *) buffer; + xdr = (__be32 *)buffer; zero = 0; #define ENCODE(x) \ do { \ - __be32 y = htonl(x); \ - if (put_user(y, xdr++) < 0) \ - goto fault; \ + *xdr++ = htonl(x); \ } while(0) #define ENCODE_DATA(l, s) \ do { \ u32 _l = (l); \ ENCODE(l); \ - if (copy_to_user(xdr, (s), _l) != 0) \ - goto fault; \ - if (_l & 3 && \ - copy_to_user((u8 __user *)xdr + _l, &zero, 4 - (_l & 3)) != 0) \ - goto fault; \ + memcpy(xdr, (s), _l); \ + if (_l & 3) \ + memcpy((u8 *)xdr + _l, &zero, 4 - (_l & 3)); \ xdr += (_l + 3) >> 2; \ } while(0) #define ENCODE64(x) \ do { \ __be64 y = cpu_to_be64(x); \ - if (copy_to_user(xdr, &y, 8) != 0) \ - goto fault; \ + memcpy(xdr, &y, 8); \ xdr += 8 >> 2; \ } while(0) #define ENCODE_STR(s) \ @@ -1240,8 +1235,4 @@ static long rxrpc_read(const struct key *key, ASSERTCMP((char __user *) xdr - buffer, ==, size); _leave(" = %zu", size); return size; - -fault: - _leave(" = -EFAULT"); - return -EFAULT; } diff --git a/security/keys/big_key.c b/security/keys/big_key.c index 2806e70..630594a 100644 --- a/security/keys/big_key.c +++ b/security/keys/big_key.c @@ -356,7 +356,7 @@ void big_key_describe(const struct key *key, struct seq_file *m) * read the key data * - the key's semaphore is read-locked */ -long big_key_read(const struct key *key, char __user *buffer, size_t buflen) +long big_key_read(const struct key *key, char *buffer, size_t buflen) { size_t datalen = (size_t)key->payload.data[big_key_len]; long ret; @@ -395,9 +395,8 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
ret = datalen;
- /* copy decrypted data to user */ - if (copy_to_user(buffer, buf->virt, datalen) != 0) - ret = -EFAULT; + /* copy out decrypted data */ + memcpy(buffer, buf->virt, datalen);
err_fput: fput(file); @@ -405,9 +404,7 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen) big_key_free_buffer(buf); } else { ret = datalen; - if (copy_to_user(buffer, key->payload.data[big_key_data], - datalen) != 0) - ret = -EFAULT; + memcpy(buffer, key->payload.data[big_key_data], datalen); }
return ret; diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index d92cbf9..571f6d4 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -895,14 +895,14 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep) }
/* - * encrypted_read - format and copy the encrypted data to userspace + * encrypted_read - format and copy out the encrypted data * * The resulting datablob format is: * <master-key name> <decrypted data length> <encrypted iv> <encrypted data> * * On success, return to userspace the encrypted key datablob size. */ -static long encrypted_read(const struct key *key, char __user *buffer, +static long encrypted_read(const struct key *key, char *buffer, size_t buflen) { struct encrypted_key_payload *epayload; @@ -950,8 +950,7 @@ static long encrypted_read(const struct key *key, char __user *buffer, key_put(mkey); memzero_explicit(derived_key, sizeof(derived_key));
- if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0) - ret = -EFAULT; + memcpy(buffer, ascii_buf, asciiblob_len); kzfree(ascii_buf);
return asciiblob_len; diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index e00e202..4b6a084 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -743,6 +743,21 @@ long keyctl_keyring_search(key_serial_t ringid, }
/* + * Call the read method + */ +static long __keyctl_read_key(struct key *key, char *buffer, size_t buflen) +{ + long ret; + + down_read(&key->sem); + ret = key_validate(key); + if (ret == 0) + ret = key->type->read(key, buffer, buflen); + up_read(&key->sem); + return ret; +} + +/* * Read a key's payload. * * The key must either grant the caller Read permission, or it must grant the @@ -757,26 +772,27 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) struct key *key; key_ref_t key_ref; long ret; + char *key_data;
/* find the key first */ key_ref = lookup_user_key(keyid, 0, 0); if (IS_ERR(key_ref)) { ret = -ENOKEY; - goto error; + goto out; }
key = key_ref_to_ptr(key_ref);
ret = key_read_state(key); if (ret < 0) - goto error2; /* Negatively instantiated */ + goto key_put_out; /* Negatively instantiated */
/* see if we can read it directly */ ret = key_permission(key_ref, KEY_NEED_READ); if (ret == 0) goto can_read_key; if (ret != -EACCES) - goto error2; + goto key_put_out;
/* we can't; see if it's searchable from this process's keyrings * - we automatically take account of the fact that it may be @@ -784,26 +800,51 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) */ if (!is_key_possessed(key_ref)) { ret = -EACCES; - goto error2; + goto key_put_out; }
/* the key is probably readable - now try to read it */ can_read_key: - ret = -EOPNOTSUPP; - if (key->type->read) { - /* Read the data with the semaphore held (since we might sleep) - * to protect against the key being updated or revoked. - */ - down_read(&key->sem); - ret = key_validate(key); - if (ret == 0) - ret = key->type->read(key, buffer, buflen); - up_read(&key->sem); + if (!key->type->read) { + ret = -EOPNOTSUPP; + goto key_put_out; }
-error2: + if (!buffer || !buflen) { + /* Get the key length from the read method */ + ret = __keyctl_read_key(key, NULL, 0); + goto key_put_out; + } + + /* + * Read the data with the semaphore held (since we might sleep) + * to protect against the key being updated or revoked. + * + * Allocating a temporary buffer to hold the keys before + * transferring them to user buffer to avoid potential + * deadlock involving page fault and mmap_sem. + */ + key_data = kmalloc(buflen, GFP_KERNEL); + + if (!key_data) { + ret = -ENOMEM; + goto key_put_out; + } + ret = __keyctl_read_key(key, key_data, buflen); + + /* + * Read methods will just return the required length without + * any copying if the provided length isn't large enough. + */ + if (ret > 0 && ret <= buflen) { + if (copy_to_user(buffer, key_data, ret)) + ret = -EFAULT; + } + kzfree(key_data); + +key_put_out: key_put(key); -error: +out: return ret; }
diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 99a5514..e8f2366 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -432,7 +432,6 @@ static int keyring_read_iterator(const void *object, void *data) { struct keyring_read_iterator_context *ctx = data; const struct key *key = keyring_ptr_to_key(object); - int ret;
kenter("{%s,%d},,{%zu/%zu}", key->type->name, key->serial, ctx->count, ctx->buflen); @@ -440,10 +439,7 @@ static int keyring_read_iterator(const void *object, void *data) if (ctx->count >= ctx->buflen) return 1;
- ret = put_user(key->serial, ctx->buffer); - if (ret < 0) - return ret; - ctx->buffer++; + *ctx->buffer++ = key->serial; ctx->count += sizeof(key->serial); return 0; } diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index 1d34b2a..13ac3b1 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -27,7 +27,7 @@ static int request_key_auth_instantiate(struct key *, static void request_key_auth_describe(const struct key *, struct seq_file *); static void request_key_auth_revoke(struct key *); static void request_key_auth_destroy(struct key *); -static long request_key_auth_read(const struct key *, char __user *, size_t); +static long request_key_auth_read(const struct key *, char *, size_t);
/* * The request-key authorisation key type definition. @@ -85,7 +85,7 @@ static void request_key_auth_describe(const struct key *key, * - the key's semaphore is read-locked */ static long request_key_auth_read(const struct key *key, - char __user *buffer, size_t buflen) + char *buffer, size_t buflen) { struct request_key_auth *rka = get_request_key_auth(key); size_t datalen; @@ -102,8 +102,7 @@ static long request_key_auth_read(const struct key *key, if (buflen > datalen) buflen = datalen;
- if (copy_to_user(buffer, rka->callout_info, buflen) != 0) - ret = -EFAULT; + memcpy(buffer, rka->callout_info, buflen); }
return ret; diff --git a/security/keys/trusted.c b/security/keys/trusted.c index 577e0104..75d50e9 100644 --- a/security/keys/trusted.c +++ b/security/keys/trusted.c @@ -1135,11 +1135,10 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep) * trusted_read - copy the sealed blob data to userspace in hex. * On success, return to userspace the trusted key datablob size. */ -static long trusted_read(const struct key *key, char __user *buffer, +static long trusted_read(const struct key *key, char *buffer, size_t buflen) { const struct trusted_key_payload *p; - char *ascii_buf; char *bufp; int i;
@@ -1148,18 +1147,9 @@ static long trusted_read(const struct key *key, char __user *buffer, return -EINVAL;
if (buffer && buflen >= 2 * p->blob_len) { - ascii_buf = kmalloc_array(2, p->blob_len, GFP_KERNEL); - if (!ascii_buf) - return -ENOMEM; - - bufp = ascii_buf; + bufp = buffer; for (i = 0; i < p->blob_len; i++) bufp = hex_byte_pack(bufp, p->blob[i]); - if (copy_to_user(buffer, ascii_buf, 2 * p->blob_len) != 0) { - kzfree(ascii_buf); - return -EFAULT; - } - kzfree(ascii_buf); } return 2 * p->blob_len; } diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c index 9f558be..0e723b6 100644 --- a/security/keys/user_defined.c +++ b/security/keys/user_defined.c @@ -172,7 +172,7 @@ void user_describe(const struct key *key, struct seq_file *m) * read the key data * - the key's semaphore is read-locked */ -long user_read(const struct key *key, char __user *buffer, size_t buflen) +long user_read(const struct key *key, char *buffer, size_t buflen) { const struct user_key_payload *upayload; long ret; @@ -185,8 +185,7 @@ long user_read(const struct key *key, char __user *buffer, size_t buflen) if (buflen > upayload->datalen) buflen = upayload->datalen;
- if (copy_to_user(buffer, upayload->data, buflen) != 0) - ret = -EFAULT; + memcpy(buffer, upayload->data, buflen); }
return ret;