Revision 472e5b056f000a778abb41f1e443de58eb259783 authored by Linus Torvalds on 02 October 2020, 02:14:36 UTC, committed by Linus Torvalds on 02 October 2020, 02:14:36 UTC
The pipe splice code still used the old model of waiting for pipe IO by
using a non-specific "pipe_wait()" that waited for any pipe event to
happen, which depended on all pipe IO being entirely serialized by the
pipe lock. So by checking the state you were waiting for, and then
adding yourself to the wait queue before dropping the lock, you were
guaranteed to see all the wakeups.
Strictly speaking, the actual wakeups were not done under the lock, but
the pipe_wait() model still worked, because since the waiter held the
lock when checking whether it should sleep, it would always see the
current state, and the wakeup was always done after updating the state.
However, commit 0ddad21d3e99 ("pipe: use exclusive waits when reading or
writing") split the single wait-queue into two, and in the process also
made the "wait for event" code wait for _two_ wait queues, and that then
showed a race with the wakers that were not serialized by the pipe lock.
It's only splice that used that "pipe_wait()" model, so the problem
wasn't obvious, but Josef Bacik reports:
"I hit a hang with fstest btrfs/187, which does a btrfs send into
/dev/null. This works by creating a pipe, the write side is given to
the kernel to write into, and the read side is handed to a thread that
splices into a file, in this case /dev/null.
The box that was hung had the write side stuck here [pipe_write] and
the read side stuck here [splice_from_pipe_next -> pipe_wait].
[ more details about pipe_wait() scenario ]
The problem is we're doing the prepare_to_wait, which sets our state
each time, however we can be woken up either with reads or writes. In
the case above we race with the WRITER waking us up, and re-set our
state to INTERRUPTIBLE, and thus never break out of schedule"
Josef had a patch that avoided the issue in pipe_wait() by just making
it set the state only once, but the deeper problem is that pipe_wait()
depends on a level of synchonization by the pipe mutex that it really
shouldn't. And the whole "wait for any pipe state change" model really
isn't very good to begin with.
So rather than trying to work around things in pipe_wait(), remove that
legacy model of "wait for arbitrary pipe event" entirely, and actually
create functions that wait for the pipe actually being readable or
writable, and can do so without depending on the pipe lock serializing
everything.
Fixes: 0ddad21d3e99 ("pipe: use exclusive waits when reading or writing")
Link: https://lore.kernel.org/linux-fsdevel/bfa88b5ad6f069b2b679316b9e495a970130416c.1601567868.git.josef@toxicpanda.com/
Reported-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-and-tested-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 44b6e23
algif_skcipher.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* algif_skcipher: User-space interface for skcipher algorithms
*
* This file provides the user-space API for symmetric key ciphers.
*
* Copyright (c) 2010 Herbert Xu <herbert@gondor.apana.org.au>
*
* The following concept of the memory management is used:
*
* The kernel maintains two SGLs, the TX SGL and the RX SGL. The TX SGL is
* filled by user space with the data submitted via sendpage/sendmsg. Filling
* up the TX SGL does not cause a crypto operation -- the data will only be
* tracked by the kernel. Upon receipt of one recvmsg call, the caller must
* provide a buffer which is tracked with the RX SGL.
*
* During the processing of the recvmsg operation, the cipher request is
* allocated and prepared. As part of the recvmsg operation, the processed
* TX buffers are extracted from the TX SGL into a separate SGL.
*
* After the completion of the crypto operation, the RX SGL and the cipher
* request is released. The extracted TX SGL parts are released together with
* the RX SGL release.
*/
#include <crypto/scatterwalk.h>
#include <crypto/skcipher.h>
#include <crypto/if_alg.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/net.h>
#include <net/sock.h>
static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg,
size_t size)
{
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);
struct sock *psk = ask->parent;
struct alg_sock *pask = alg_sk(psk);
struct crypto_skcipher *tfm = pask->private;
unsigned ivsize = crypto_skcipher_ivsize(tfm);
return af_alg_sendmsg(sock, msg, size, ivsize);
}
static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
size_t ignored, int flags)
{
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);
struct sock *psk = ask->parent;
struct alg_sock *pask = alg_sk(psk);
struct af_alg_ctx *ctx = ask->private;
struct crypto_skcipher *tfm = pask->private;
unsigned int bs = crypto_skcipher_chunksize(tfm);
struct af_alg_async_req *areq;
int err = 0;
size_t len = 0;
if (!ctx->init || (ctx->more && ctx->used < bs)) {
err = af_alg_wait_for_data(sk, flags, bs);
if (err)
return err;
}
/* Allocate cipher request for current operation. */
areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
crypto_skcipher_reqsize(tfm));
if (IS_ERR(areq))
return PTR_ERR(areq);
/* convert iovecs of output buffers into RX SGL */
err = af_alg_get_rsgl(sk, msg, flags, areq, ctx->used, &len);
if (err)
goto free;
/*
* If more buffers are to be expected to be processed, process only
* full block size buffers.
*/
if (ctx->more || len < ctx->used)
len -= len % bs;
/*
* Create a per request TX SGL for this request which tracks the
* SG entries from the global TX SGL.
*/
areq->tsgl_entries = af_alg_count_tsgl(sk, len, 0);
if (!areq->tsgl_entries)
areq->tsgl_entries = 1;
areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
areq->tsgl_entries),
GFP_KERNEL);
if (!areq->tsgl) {
err = -ENOMEM;
goto free;
}
sg_init_table(areq->tsgl, areq->tsgl_entries);
af_alg_pull_tsgl(sk, len, areq->tsgl, 0);
/* Initialize the crypto operation */
skcipher_request_set_tfm(&areq->cra_u.skcipher_req, tfm);
skcipher_request_set_crypt(&areq->cra_u.skcipher_req, areq->tsgl,
areq->first_rsgl.sgl.sg, len, ctx->iv);
if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
/* AIO operation */
sock_hold(sk);
areq->iocb = msg->msg_iocb;
/* Remember output size that will be generated. */
areq->outlen = len;
skcipher_request_set_callback(&areq->cra_u.skcipher_req,
CRYPTO_TFM_REQ_MAY_SLEEP,
af_alg_async_cb, areq);
err = ctx->enc ?
crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
crypto_skcipher_decrypt(&areq->cra_u.skcipher_req);
/* AIO operation in progress */
if (err == -EINPROGRESS || err == -EBUSY)
return -EIOCBQUEUED;
sock_put(sk);
} else {
/* Synchronous operation */
skcipher_request_set_callback(&areq->cra_u.skcipher_req,
CRYPTO_TFM_REQ_MAY_SLEEP |
CRYPTO_TFM_REQ_MAY_BACKLOG,
crypto_req_done, &ctx->wait);
err = crypto_wait_req(ctx->enc ?
crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
crypto_skcipher_decrypt(&areq->cra_u.skcipher_req),
&ctx->wait);
}
free:
af_alg_free_resources(areq);
return err ? err : len;
}
static int skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
size_t ignored, int flags)
{
struct sock *sk = sock->sk;
int ret = 0;
lock_sock(sk);
while (msg_data_left(msg)) {
int err = _skcipher_recvmsg(sock, msg, ignored, flags);
/*
* This error covers -EIOCBQUEUED which implies that we can
* only handle one AIO request. If the caller wants to have
* multiple AIO requests in parallel, he must make multiple
* separate AIO calls.
*
* Also return the error if no data has been processed so far.
*/
if (err <= 0) {
if (err == -EIOCBQUEUED || !ret)
ret = err;
goto out;
}
ret += err;
}
out:
af_alg_wmem_wakeup(sk);
release_sock(sk);
return ret;
}
static struct proto_ops algif_skcipher_ops = {
.family = PF_ALG,
.connect = sock_no_connect,
.socketpair = sock_no_socketpair,
.getname = sock_no_getname,
.ioctl = sock_no_ioctl,
.listen = sock_no_listen,
.shutdown = sock_no_shutdown,
.mmap = sock_no_mmap,
.bind = sock_no_bind,
.accept = sock_no_accept,
.release = af_alg_release,
.sendmsg = skcipher_sendmsg,
.sendpage = af_alg_sendpage,
.recvmsg = skcipher_recvmsg,
.poll = af_alg_poll,
};
static int skcipher_check_key(struct socket *sock)
{
int err = 0;
struct sock *psk;
struct alg_sock *pask;
struct crypto_skcipher *tfm;
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);
lock_sock(sk);
if (!atomic_read(&ask->nokey_refcnt))
goto unlock_child;
psk = ask->parent;
pask = alg_sk(ask->parent);
tfm = pask->private;
err = -ENOKEY;
lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
goto unlock;
atomic_dec(&pask->nokey_refcnt);
atomic_set(&ask->nokey_refcnt, 0);
err = 0;
unlock:
release_sock(psk);
unlock_child:
release_sock(sk);
return err;
}
static int skcipher_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
size_t size)
{
int err;
err = skcipher_check_key(sock);
if (err)
return err;
return skcipher_sendmsg(sock, msg, size);
}
static ssize_t skcipher_sendpage_nokey(struct socket *sock, struct page *page,
int offset, size_t size, int flags)
{
int err;
err = skcipher_check_key(sock);
if (err)
return err;
return af_alg_sendpage(sock, page, offset, size, flags);
}
static int skcipher_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
size_t ignored, int flags)
{
int err;
err = skcipher_check_key(sock);
if (err)
return err;
return skcipher_recvmsg(sock, msg, ignored, flags);
}
static struct proto_ops algif_skcipher_ops_nokey = {
.family = PF_ALG,
.connect = sock_no_connect,
.socketpair = sock_no_socketpair,
.getname = sock_no_getname,
.ioctl = sock_no_ioctl,
.listen = sock_no_listen,
.shutdown = sock_no_shutdown,
.mmap = sock_no_mmap,
.bind = sock_no_bind,
.accept = sock_no_accept,
.release = af_alg_release,
.sendmsg = skcipher_sendmsg_nokey,
.sendpage = skcipher_sendpage_nokey,
.recvmsg = skcipher_recvmsg_nokey,
.poll = af_alg_poll,
};
static void *skcipher_bind(const char *name, u32 type, u32 mask)
{
return crypto_alloc_skcipher(name, type, mask);
}
static void skcipher_release(void *private)
{
crypto_free_skcipher(private);
}
static int skcipher_setkey(void *private, const u8 *key, unsigned int keylen)
{
return crypto_skcipher_setkey(private, key, keylen);
}
static void skcipher_sock_destruct(struct sock *sk)
{
struct alg_sock *ask = alg_sk(sk);
struct af_alg_ctx *ctx = ask->private;
struct sock *psk = ask->parent;
struct alg_sock *pask = alg_sk(psk);
struct crypto_skcipher *tfm = pask->private;
af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
sock_kzfree_s(sk, ctx->iv, crypto_skcipher_ivsize(tfm));
sock_kfree_s(sk, ctx, ctx->len);
af_alg_release_parent(sk);
}
static int skcipher_accept_parent_nokey(void *private, struct sock *sk)
{
struct af_alg_ctx *ctx;
struct alg_sock *ask = alg_sk(sk);
struct crypto_skcipher *tfm = private;
unsigned int len = sizeof(*ctx);
ctx = sock_kmalloc(sk, len, GFP_KERNEL);
if (!ctx)
return -ENOMEM;
memset(ctx, 0, len);
ctx->iv = sock_kmalloc(sk, crypto_skcipher_ivsize(tfm),
GFP_KERNEL);
if (!ctx->iv) {
sock_kfree_s(sk, ctx, len);
return -ENOMEM;
}
memset(ctx->iv, 0, crypto_skcipher_ivsize(tfm));
INIT_LIST_HEAD(&ctx->tsgl_list);
ctx->len = len;
crypto_init_wait(&ctx->wait);
ask->private = ctx;
sk->sk_destruct = skcipher_sock_destruct;
return 0;
}
static int skcipher_accept_parent(void *private, struct sock *sk)
{
struct crypto_skcipher *tfm = private;
if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
return -ENOKEY;
return skcipher_accept_parent_nokey(private, sk);
}
static const struct af_alg_type algif_type_skcipher = {
.bind = skcipher_bind,
.release = skcipher_release,
.setkey = skcipher_setkey,
.accept = skcipher_accept_parent,
.accept_nokey = skcipher_accept_parent_nokey,
.ops = &algif_skcipher_ops,
.ops_nokey = &algif_skcipher_ops_nokey,
.name = "skcipher",
.owner = THIS_MODULE
};
static int __init algif_skcipher_init(void)
{
return af_alg_register_type(&algif_type_skcipher);
}
static void __exit algif_skcipher_exit(void)
{
int err = af_alg_unregister_type(&algif_type_skcipher);
BUG_ON(err);
}
module_init(algif_skcipher_init);
module_exit(algif_skcipher_exit);
MODULE_LICENSE("GPL");
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