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idryomovidryomov
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libceph: stop allocating a new cipher on every crypto request
This is useless and more importantly not allowed on the writeback path, because crypto_alloc_skcipher() allocates memory with GFP_KERNEL, which can recurse back into the filesystem: kworker/9:3 D ffff92303f318180 0 20732 2 0x00000080 Workqueue: ceph-msgr ceph_con_workfn [libceph] ffff923035dd4480 ffff923038f8a0c0 0000000000000001 000000009eb27318 ffff92269eb28000 ffff92269eb27338 ffff923036b145ac ffff923035dd4480 00000000ffffffff ffff923036b145b0 ffffffff951eb4e1 ffff923036b145a8 Call Trace: [<ffffffff951eb4e1>] ? schedule+0x31/0x80 [<ffffffff951eb77a>] ? schedule_preempt_disabled+0xa/0x10 [<ffffffff951ed1f4>] ? __mutex_lock_slowpath+0xb4/0x130 [<ffffffff951ed28b>] ? mutex_lock+0x1b/0x30 [<ffffffffc0a974b3>] ? xfs_reclaim_inodes_ag+0x233/0x2d0 [xfs] [<ffffffff94d92ba5>] ? move_active_pages_to_lru+0x125/0x270 [<ffffffff94f2b985>] ? radix_tree_gang_lookup_tag+0xc5/0x1c0 [<ffffffff94dad0f3>] ? __list_lru_walk_one.isra.3+0x33/0x120 [<ffffffffc0a98331>] ? xfs_reclaim_inodes_nr+0x31/0x40 [xfs] [<ffffffff94e05bfe>] ? super_cache_scan+0x17e/0x190 [<ffffffff94d919f3>] ? shrink_slab.part.38+0x1e3/0x3d0 [<ffffffff94d9616a>] ? shrink_node+0x10a/0x320 [<ffffffff94d96474>] ? do_try_to_free_pages+0xf4/0x350 [<ffffffff94d967ba>] ? try_to_free_pages+0xea/0x1b0 [<ffffffff94d863bd>] ? __alloc_pages_nodemask+0x61d/0xe60 [<ffffffff94ddf42d>] ? cache_grow_begin+0x9d/0x560 [<ffffffff94ddfb88>] ? fallback_alloc+0x148/0x1c0 [<ffffffff94ed84e7>] ? __crypto_alloc_tfm+0x37/0x130 [<ffffffff94de09db>] ? __kmalloc+0x1eb/0x580 [<ffffffffc09fe2db>] ? crush_choose_firstn+0x3eb/0x470 [libceph] [<ffffffff94ed84e7>] ? __crypto_alloc_tfm+0x37/0x130 [<ffffffff94ed9c19>] ? crypto_spawn_tfm+0x39/0x60 [<ffffffffc08b30a3>] ? crypto_cbc_init_tfm+0x23/0x40 [cbc] [<ffffffff94ed857c>] ? __crypto_alloc_tfm+0xcc/0x130 [<ffffffff94edcc23>] ? crypto_skcipher_init_tfm+0x113/0x180 [<ffffffff94ed7cc3>] ? crypto_create_tfm+0x43/0xb0 [<ffffffff94ed83b0>] ? crypto_larval_lookup+0x150/0x150 [<ffffffff94ed7da2>] ? crypto_alloc_tfm+0x72/0x120 [<ffffffffc0a01dd7>] ? ceph_aes_encrypt2+0x67/0x400 [libceph] [<ffffffffc09fd264>] ? ceph_pg_to_up_acting_osds+0x84/0x5b0 [libceph] [<ffffffff950d40a0>] ? release_sock+0x40/0x90 [<ffffffff95139f94>] ? tcp_recvmsg+0x4b4/0xae0 [<ffffffffc0a02714>] ? ceph_encrypt2+0x54/0xc0 [libceph] [<ffffffffc0a02b4d>] ? ceph_x_encrypt+0x5d/0x90 [libceph] [<ffffffffc0a02bdf>] ? calcu_signature+0x5f/0x90 [libceph] [<ffffffffc0a02ef5>] ? ceph_x_sign_message+0x35/0x50 [libceph] [<ffffffffc09e948c>] ? prepare_write_message_footer+0x5c/0xa0 [libceph] [<ffffffffc09ecd18>] ? ceph_con_workfn+0x2258/0x2dd0 [libceph] [<ffffffffc09e9903>] ? queue_con_delay+0x33/0xd0 [libceph] [<ffffffffc09f68ed>] ? __submit_request+0x20d/0x2f0 [libceph] [<ffffffffc09f6ef8>] ? ceph_osdc_start_request+0x28/0x30 [libceph] [<ffffffffc0b52603>] ? rbd_queue_workfn+0x2f3/0x350 [rbd] [<ffffffff94c94ec0>] ? process_one_work+0x160/0x410 [<ffffffff94c951bd>] ? worker_thread+0x4d/0x480 [<ffffffff94c95170>] ? process_one_work+0x410/0x410 [<ffffffff94c9af8d>] ? kthread+0xcd/0xf0 [<ffffffff951efb2f>] ? ret_from_fork+0x1f/0x40 [<ffffffff94c9aec0>] ? kthread_create_on_node+0x190/0x190 Allocating the cipher along with the key fixes the issue - as long the key doesn't change, a single cipher context can be used concurrently in multiple requests. We still can't take that GFP_KERNEL allocation though. Both ceph_crypto_key_clone() and ceph_crypto_key_decode() are called from GFP_NOFS context, so resort to memalloc_noio_{save,restore}() here. Reported-by: Lucas Stach <l.stach@pengutronix.de> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Sage Weil <sage@redhat.com>
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-25
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2 files changed

+61
-25
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‎net/ceph/crypto.c

Lines changed: 60 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -13,14 +13,60 @@
1313
#include <linux/ceph/decode.h>
1414
#include "crypto.h"
1515

16+
/*
17+
* Set ->key and ->tfm. The rest of the key should be filled in before
18+
* this function is called.
19+
*/
20+
static int set_secret(struct ceph_crypto_key *key, void *buf)
21+
{
22+
unsigned int noio_flag;
23+
int ret;
24+
25+
key->key = NULL;
26+
key->tfm = NULL;
27+
28+
switch (key->type) {
29+
case CEPH_CRYPTO_NONE:
30+
return 0; /* nothing to do */
31+
case CEPH_CRYPTO_AES:
32+
break;
33+
default:
34+
return -ENOTSUPP;
35+
}
36+
37+
WARN_ON(!key->len);
38+
key->key = kmemdup(buf, key->len, GFP_NOIO);
39+
if (!key->key) {
40+
ret = -ENOMEM;
41+
goto fail;
42+
}
43+
44+
/* crypto_alloc_skcipher() allocates with GFP_KERNEL */
45+
noio_flag = memalloc_noio_save();
46+
key->tfm = crypto_alloc_skcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC);
47+
memalloc_noio_restore(noio_flag);
48+
if (IS_ERR(key->tfm)) {
49+
ret = PTR_ERR(key->tfm);
50+
key->tfm = NULL;
51+
goto fail;
52+
}
53+
54+
ret = crypto_skcipher_setkey(key->tfm, key->key, key->len);
55+
if (ret)
56+
goto fail;
57+
58+
return 0;
59+
60+
fail:
61+
ceph_crypto_key_destroy(key);
62+
return ret;
63+
}
64+
1665
int ceph_crypto_key_clone(struct ceph_crypto_key *dst,
1766
const struct ceph_crypto_key *src)
1867
{
1968
memcpy(dst, src, sizeof(struct ceph_crypto_key));
20-
dst->key = kmemdup(src->key, src->len, GFP_NOFS);
21-
if (!dst->key)
22-
return -ENOMEM;
23-
return 0;
69+
return set_secret(dst, src->key);
2470
}
2571

2672
int ceph_crypto_key_encode(struct ceph_crypto_key *key, void **p, void *end)
@@ -37,16 +83,16 @@ int ceph_crypto_key_encode(struct ceph_crypto_key *key, void **p, void *end)
3783

3884
int ceph_crypto_key_decode(struct ceph_crypto_key *key, void **p, void *end)
3985
{
86+
int ret;
87+
4088
ceph_decode_need(p, end, 2*sizeof(u16) + sizeof(key->created), bad);
4189
key->type = ceph_decode_16(p);
4290
ceph_decode_copy(p, &key->created, sizeof(key->created));
4391
key->len = ceph_decode_16(p);
4492
ceph_decode_need(p, end, key->len, bad);
45-
key->key = kmalloc(key->len, GFP_NOFS);
46-
if (!key->key)
47-
return -ENOMEM;
48-
ceph_decode_copy(p, key->key, key->len);
49-
return 0;
93+
ret = set_secret(key, *p);
94+
*p += key->len;
95+
return ret;
5096

5197
bad:
5298
dout("failed to decode crypto key\n");
@@ -85,14 +131,11 @@ void ceph_crypto_key_destroy(struct ceph_crypto_key *key)
85131
if (key) {
86132
kfree(key->key);
87133
key->key = NULL;
134+
crypto_free_skcipher(key->tfm);
135+
key->tfm = NULL;
88136
}
89137
}
90138

91-
static struct crypto_skcipher *ceph_crypto_alloc_cipher(void)
92-
{
93-
return crypto_alloc_skcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC);
94-
}
95-
96139
static const u8 *aes_iv = (u8 *)CEPH_AES_IV;
97140

98141
/*
@@ -168,29 +211,23 @@ static void teardown_sgtable(struct sg_table *sgt)
168211
static int ceph_aes_crypt(const struct ceph_crypto_key *key, bool encrypt,
169212
void *buf, int buf_len, int in_len, int *pout_len)
170213
{
171-
struct crypto_skcipher *tfm = ceph_crypto_alloc_cipher();
172-
SKCIPHER_REQUEST_ON_STACK(req, tfm);
214+
SKCIPHER_REQUEST_ON_STACK(req, key->tfm);
173215
struct sg_table sgt;
174216
struct scatterlist prealloc_sg;
175217
char iv[AES_BLOCK_SIZE];
176218
int pad_byte = AES_BLOCK_SIZE - (in_len & (AES_BLOCK_SIZE - 1));
177219
int crypt_len = encrypt ? in_len + pad_byte : in_len;
178220
int ret;
179221

180-
if (IS_ERR(tfm))
181-
return PTR_ERR(tfm);
182-
183222
WARN_ON(crypt_len > buf_len);
184223
if (encrypt)
185224
memset(buf + in_len, pad_byte, pad_byte);
186225
ret = setup_sgtable(&sgt, &prealloc_sg, buf, crypt_len);
187226
if (ret)
188-
goto out_tfm;
227+
return ret;
189228

190-
crypto_skcipher_setkey((void *)tfm, key->key, key->len);
191229
memcpy(iv, aes_iv, AES_BLOCK_SIZE);
192-
193-
skcipher_request_set_tfm(req, tfm);
230+
skcipher_request_set_tfm(req, key->tfm);
194231
skcipher_request_set_callback(req, 0, NULL, NULL);
195232
skcipher_request_set_crypt(req, sgt.sgl, sgt.sgl, crypt_len, iv);
196233

@@ -232,8 +269,6 @@ static int ceph_aes_crypt(const struct ceph_crypto_key *key, bool encrypt,
232269

233270
out_sgt:
234271
teardown_sgtable(&sgt);
235-
out_tfm:
236-
crypto_free_skcipher(tfm);
237272
return ret;
238273
}
239274

‎net/ceph/crypto.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,7 @@ struct ceph_crypto_key {
1212
struct ceph_timespec created;
1313
int len;
1414
void *key;
15+
struct crypto_skcipher *tfm;
1516
};
1617

1718
int ceph_crypto_key_clone(struct ceph_crypto_key *dst,

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