Revision 4f988f152ee087831ea5c1c77cda4454cacc052c authored by Linus Torvalds on 04 May 2012, 22:13:54 UTC, committed by Linus Torvalds on 04 May 2012, 22:13:54 UTC
The normal read_seqcount_begin() function will wait for any current writers to exit their critical region by looping until the sequence count is even. That "wait for sequence count to stabilize" is the right thing to do if the read-locker will just retry the whole operation on contention: no point in doing a potentially expensive reader sequence if we know at the beginning that we'll just end up re-doing it all. HOWEVER. Some users don't actually retry the operation, but instead will abort and do the operation with proper locking. So the sequence count case may be the optimistic quick case, but in the presense of writers you may want to do full locking in order to guarantee forward progress. The prime example of this would be the RCU name lookup. And in that case, you may well be better off without the "retry early", and are in a rush to instead get to the failure handling. Thus this "raw" interface that just returns the sequence number without testing it - it just forces the low bit to zero so that read_seqcount_retry() will always fail such a "active concurrent writer" scenario. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 2f62427
algif_skcipher.c
/*
* 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>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#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>
struct skcipher_sg_list {
struct list_head list;
int cur;
struct scatterlist sg[0];
};
struct skcipher_ctx {
struct list_head tsgl;
struct af_alg_sgl rsgl;
void *iv;
struct af_alg_completion completion;
unsigned used;
unsigned int len;
bool more;
bool merge;
bool enc;
struct ablkcipher_request req;
};
#define MAX_SGL_ENTS ((PAGE_SIZE - sizeof(struct skcipher_sg_list)) / \
sizeof(struct scatterlist) - 1)
static inline int skcipher_sndbuf(struct sock *sk)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
return max_t(int, max_t(int, sk->sk_sndbuf & PAGE_MASK, PAGE_SIZE) -
ctx->used, 0);
}
static inline bool skcipher_writable(struct sock *sk)
{
return PAGE_SIZE <= skcipher_sndbuf(sk);
}
static int skcipher_alloc_sgl(struct sock *sk)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
struct skcipher_sg_list *sgl;
struct scatterlist *sg = NULL;
sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
if (!list_empty(&ctx->tsgl))
sg = sgl->sg;
if (!sg || sgl->cur >= MAX_SGL_ENTS) {
sgl = sock_kmalloc(sk, sizeof(*sgl) +
sizeof(sgl->sg[0]) * (MAX_SGL_ENTS + 1),
GFP_KERNEL);
if (!sgl)
return -ENOMEM;
sg_init_table(sgl->sg, MAX_SGL_ENTS + 1);
sgl->cur = 0;
if (sg)
scatterwalk_sg_chain(sg, MAX_SGL_ENTS + 1, sgl->sg);
list_add_tail(&sgl->list, &ctx->tsgl);
}
return 0;
}
static void skcipher_pull_sgl(struct sock *sk, int used)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
struct skcipher_sg_list *sgl;
struct scatterlist *sg;
int i;
while (!list_empty(&ctx->tsgl)) {
sgl = list_first_entry(&ctx->tsgl, struct skcipher_sg_list,
list);
sg = sgl->sg;
for (i = 0; i < sgl->cur; i++) {
int plen = min_t(int, used, sg[i].length);
if (!sg_page(sg + i))
continue;
sg[i].length -= plen;
sg[i].offset += plen;
used -= plen;
ctx->used -= plen;
if (sg[i].length)
return;
put_page(sg_page(sg + i));
sg_assign_page(sg + i, NULL);
}
list_del(&sgl->list);
sock_kfree_s(sk, sgl,
sizeof(*sgl) + sizeof(sgl->sg[0]) *
(MAX_SGL_ENTS + 1));
}
if (!ctx->used)
ctx->merge = 0;
}
static void skcipher_free_sgl(struct sock *sk)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
skcipher_pull_sgl(sk, ctx->used);
}
static int skcipher_wait_for_wmem(struct sock *sk, unsigned flags)
{
long timeout;
DEFINE_WAIT(wait);
int err = -ERESTARTSYS;
if (flags & MSG_DONTWAIT)
return -EAGAIN;
set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
for (;;) {
if (signal_pending(current))
break;
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
timeout = MAX_SCHEDULE_TIMEOUT;
if (sk_wait_event(sk, &timeout, skcipher_writable(sk))) {
err = 0;
break;
}
}
finish_wait(sk_sleep(sk), &wait);
return err;
}
static void skcipher_wmem_wakeup(struct sock *sk)
{
struct socket_wq *wq;
if (!skcipher_writable(sk))
return;
rcu_read_lock();
wq = rcu_dereference(sk->sk_wq);
if (wq_has_sleeper(wq))
wake_up_interruptible_sync_poll(&wq->wait, POLLIN |
POLLRDNORM |
POLLRDBAND);
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
rcu_read_unlock();
}
static int skcipher_wait_for_data(struct sock *sk, unsigned flags)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
long timeout;
DEFINE_WAIT(wait);
int err = -ERESTARTSYS;
if (flags & MSG_DONTWAIT) {
return -EAGAIN;
}
set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
for (;;) {
if (signal_pending(current))
break;
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
timeout = MAX_SCHEDULE_TIMEOUT;
if (sk_wait_event(sk, &timeout, ctx->used)) {
err = 0;
break;
}
}
finish_wait(sk_sleep(sk), &wait);
clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
return err;
}
static void skcipher_data_wakeup(struct sock *sk)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
struct socket_wq *wq;
if (!ctx->used)
return;
rcu_read_lock();
wq = rcu_dereference(sk->sk_wq);
if (wq_has_sleeper(wq))
wake_up_interruptible_sync_poll(&wq->wait, POLLOUT |
POLLRDNORM |
POLLRDBAND);
sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
rcu_read_unlock();
}
static int skcipher_sendmsg(struct kiocb *unused, struct socket *sock,
struct msghdr *msg, size_t size)
{
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
struct crypto_ablkcipher *tfm = crypto_ablkcipher_reqtfm(&ctx->req);
unsigned ivsize = crypto_ablkcipher_ivsize(tfm);
struct skcipher_sg_list *sgl;
struct af_alg_control con = {};
long copied = 0;
bool enc = 0;
int err;
int i;
if (msg->msg_controllen) {
err = af_alg_cmsg_send(msg, &con);
if (err)
return err;
switch (con.op) {
case ALG_OP_ENCRYPT:
enc = 1;
break;
case ALG_OP_DECRYPT:
enc = 0;
break;
default:
return -EINVAL;
}
if (con.iv && con.iv->ivlen != ivsize)
return -EINVAL;
}
err = -EINVAL;
lock_sock(sk);
if (!ctx->more && ctx->used)
goto unlock;
if (!ctx->used) {
ctx->enc = enc;
if (con.iv)
memcpy(ctx->iv, con.iv->iv, ivsize);
}
while (size) {
struct scatterlist *sg;
unsigned long len = size;
int plen;
if (ctx->merge) {
sgl = list_entry(ctx->tsgl.prev,
struct skcipher_sg_list, list);
sg = sgl->sg + sgl->cur - 1;
len = min_t(unsigned long, len,
PAGE_SIZE - sg->offset - sg->length);
err = memcpy_fromiovec(page_address(sg_page(sg)) +
sg->offset + sg->length,
msg->msg_iov, len);
if (err)
goto unlock;
sg->length += len;
ctx->merge = (sg->offset + sg->length) &
(PAGE_SIZE - 1);
ctx->used += len;
copied += len;
size -= len;
continue;
}
if (!skcipher_writable(sk)) {
err = skcipher_wait_for_wmem(sk, msg->msg_flags);
if (err)
goto unlock;
}
len = min_t(unsigned long, len, skcipher_sndbuf(sk));
err = skcipher_alloc_sgl(sk);
if (err)
goto unlock;
sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
sg = sgl->sg;
do {
i = sgl->cur;
plen = min_t(int, len, PAGE_SIZE);
sg_assign_page(sg + i, alloc_page(GFP_KERNEL));
err = -ENOMEM;
if (!sg_page(sg + i))
goto unlock;
err = memcpy_fromiovec(page_address(sg_page(sg + i)),
msg->msg_iov, plen);
if (err) {
__free_page(sg_page(sg + i));
sg_assign_page(sg + i, NULL);
goto unlock;
}
sg[i].length = plen;
len -= plen;
ctx->used += plen;
copied += plen;
size -= plen;
sgl->cur++;
} while (len && sgl->cur < MAX_SGL_ENTS);
ctx->merge = plen & (PAGE_SIZE - 1);
}
err = 0;
ctx->more = msg->msg_flags & MSG_MORE;
if (!ctx->more && !list_empty(&ctx->tsgl))
sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
unlock:
skcipher_data_wakeup(sk);
release_sock(sk);
return copied ?: err;
}
static ssize_t skcipher_sendpage(struct socket *sock, struct page *page,
int offset, size_t size, int flags)
{
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
struct skcipher_sg_list *sgl;
int err = -EINVAL;
lock_sock(sk);
if (!ctx->more && ctx->used)
goto unlock;
if (!size)
goto done;
if (!skcipher_writable(sk)) {
err = skcipher_wait_for_wmem(sk, flags);
if (err)
goto unlock;
}
err = skcipher_alloc_sgl(sk);
if (err)
goto unlock;
ctx->merge = 0;
sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
get_page(page);
sg_set_page(sgl->sg + sgl->cur, page, size, offset);
sgl->cur++;
ctx->used += size;
done:
ctx->more = flags & MSG_MORE;
if (!ctx->more && !list_empty(&ctx->tsgl))
sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
unlock:
skcipher_data_wakeup(sk);
release_sock(sk);
return err ?: size;
}
static int skcipher_recvmsg(struct kiocb *unused, struct socket *sock,
struct msghdr *msg, size_t ignored, int flags)
{
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
unsigned bs = crypto_ablkcipher_blocksize(crypto_ablkcipher_reqtfm(
&ctx->req));
struct skcipher_sg_list *sgl;
struct scatterlist *sg;
unsigned long iovlen;
struct iovec *iov;
int err = -EAGAIN;
int used;
long copied = 0;
lock_sock(sk);
for (iov = msg->msg_iov, iovlen = msg->msg_iovlen; iovlen > 0;
iovlen--, iov++) {
unsigned long seglen = iov->iov_len;
char __user *from = iov->iov_base;
while (seglen) {
sgl = list_first_entry(&ctx->tsgl,
struct skcipher_sg_list, list);
sg = sgl->sg;
while (!sg->length)
sg++;
used = ctx->used;
if (!used) {
err = skcipher_wait_for_data(sk, flags);
if (err)
goto unlock;
}
used = min_t(unsigned long, used, seglen);
used = af_alg_make_sg(&ctx->rsgl, from, used, 1);
err = used;
if (err < 0)
goto unlock;
if (ctx->more || used < ctx->used)
used -= used % bs;
err = -EINVAL;
if (!used)
goto free;
ablkcipher_request_set_crypt(&ctx->req, sg,
ctx->rsgl.sg, used,
ctx->iv);
err = af_alg_wait_for_completion(
ctx->enc ?
crypto_ablkcipher_encrypt(&ctx->req) :
crypto_ablkcipher_decrypt(&ctx->req),
&ctx->completion);
free:
af_alg_free_sg(&ctx->rsgl);
if (err)
goto unlock;
copied += used;
from += used;
seglen -= used;
skcipher_pull_sgl(sk, used);
}
}
err = 0;
unlock:
skcipher_wmem_wakeup(sk);
release_sock(sk);
return copied ?: err;
}
static unsigned int skcipher_poll(struct file *file, struct socket *sock,
poll_table *wait)
{
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
unsigned int mask;
sock_poll_wait(file, sk_sleep(sk), wait);
mask = 0;
if (ctx->used)
mask |= POLLIN | POLLRDNORM;
if (skcipher_writable(sk))
mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
return mask;
}
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,
.getsockopt = sock_no_getsockopt,
.mmap = sock_no_mmap,
.bind = sock_no_bind,
.accept = sock_no_accept,
.setsockopt = sock_no_setsockopt,
.release = af_alg_release,
.sendmsg = skcipher_sendmsg,
.sendpage = skcipher_sendpage,
.recvmsg = skcipher_recvmsg,
.poll = skcipher_poll,
};
static void *skcipher_bind(const char *name, u32 type, u32 mask)
{
return crypto_alloc_ablkcipher(name, type, mask);
}
static void skcipher_release(void *private)
{
crypto_free_ablkcipher(private);
}
static int skcipher_setkey(void *private, const u8 *key, unsigned int keylen)
{
return crypto_ablkcipher_setkey(private, key, keylen);
}
static void skcipher_sock_destruct(struct sock *sk)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
struct crypto_ablkcipher *tfm = crypto_ablkcipher_reqtfm(&ctx->req);
skcipher_free_sgl(sk);
sock_kfree_s(sk, ctx->iv, crypto_ablkcipher_ivsize(tfm));
sock_kfree_s(sk, ctx, ctx->len);
af_alg_release_parent(sk);
}
static int skcipher_accept_parent(void *private, struct sock *sk)
{
struct skcipher_ctx *ctx;
struct alg_sock *ask = alg_sk(sk);
unsigned int len = sizeof(*ctx) + crypto_ablkcipher_reqsize(private);
ctx = sock_kmalloc(sk, len, GFP_KERNEL);
if (!ctx)
return -ENOMEM;
ctx->iv = sock_kmalloc(sk, crypto_ablkcipher_ivsize(private),
GFP_KERNEL);
if (!ctx->iv) {
sock_kfree_s(sk, ctx, len);
return -ENOMEM;
}
memset(ctx->iv, 0, crypto_ablkcipher_ivsize(private));
INIT_LIST_HEAD(&ctx->tsgl);
ctx->len = len;
ctx->used = 0;
ctx->more = 0;
ctx->merge = 0;
ctx->enc = 0;
af_alg_init_completion(&ctx->completion);
ask->private = ctx;
ablkcipher_request_set_tfm(&ctx->req, private);
ablkcipher_request_set_callback(&ctx->req, CRYPTO_TFM_REQ_MAY_BACKLOG,
af_alg_complete, &ctx->completion);
sk->sk_destruct = skcipher_sock_destruct;
return 0;
}
static const struct af_alg_type algif_type_skcipher = {
.bind = skcipher_bind,
.release = skcipher_release,
.setkey = skcipher_setkey,
.accept = skcipher_accept_parent,
.ops = &algif_skcipher_ops,
.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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