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linux_kernel/lib/kfifo.c
Linus Torvalds ab9bb6318b Partially revert "kfifo: fix kfifo_alloc() and kfifo_init()" 
Commit dfe2a77fd2 ("kfifo: fix kfifo_alloc() and kfifo_init()") made
the kfifo code round the number of elements up.  That was good for
__kfifo_alloc(), but it's actually wrong for __kfifo_init().

The difference? __kfifo_alloc() will allocate the rounded-up number of
elements, but __kfifo_init() uses an allocation done by the caller.  We
can't just say "use more elements than the caller allocated", and have
to round down.

The good news? All the normal cases will be using power-of-two arrays
anyway, and most users of kfifo's don't use kfifo_init() at all, but one
of the helper macros to declare a KFIFO that enforce the proper
power-of-two behavior.  But it looks like at least ibmvscsis might be
affected.

The bad news? Will Deacon refers to an old thread and points points out
that the memory ordering in kfifo's is questionable.  See

  https://lore.kernel.org/lkml/20181211034032.32338-1-yuleixzhang@tencent.com/

for more.

Fixes: dfe2a77fd2 ("kfifo: fix kfifo_alloc() and kfifo_init()")
Reported-by: laokz <laokz@foxmail.com>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Greg KH <greg@kroah.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-08-30 18:47:15 -07:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* A generic kernel FIFO implementation
*
* Copyright (C) 2009/2010 Stefani Seibold <stefani@seibold.net>
*/
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/log2.h>
#include <linux/uaccess.h>
#include <linux/kfifo.h>
/*
* internal helper to calculate the unused elements in a fifo
*/
static inline unsigned int kfifo_unused(struct __kfifo *fifo)
{
return (fifo->mask + 1) - (fifo->in - fifo->out);
}
int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
size_t esize, gfp_t gfp_mask)
{
/*
* round up to the next power of 2, since our 'let the indices
* wrap' technique works only in this case.
*/
size = roundup_pow_of_two(size);
fifo->in = 0;
fifo->out = 0;
fifo->esize = esize;
if (size < 2) {
fifo->data = NULL;
fifo->mask = 0;
return -EINVAL;
}
fifo->data = kmalloc_array(esize, size, gfp_mask);
if (!fifo->data) {
fifo->mask = 0;
return -ENOMEM;
}
fifo->mask = size - 1;
return 0;
}
EXPORT_SYMBOL(__kfifo_alloc);
void __kfifo_free(struct __kfifo *fifo)
{
kfree(fifo->data);
fifo->in = 0;
fifo->out = 0;
fifo->esize = 0;
fifo->data = NULL;
fifo->mask = 0;
}
EXPORT_SYMBOL(__kfifo_free);
int __kfifo_init(struct __kfifo *fifo, void *buffer,
unsigned int size, size_t esize)
{
size /= esize;
if (!is_power_of_2(size))
size = rounddown_pow_of_two(size);
fifo->in = 0;
fifo->out = 0;
fifo->esize = esize;
fifo->data = buffer;
if (size < 2) {
fifo->mask = 0;
return -EINVAL;
}
fifo->mask = size - 1;
return 0;
}
EXPORT_SYMBOL(__kfifo_init);
static void kfifo_copy_in(struct __kfifo *fifo, const void *src,
unsigned int len, unsigned int off)
{
unsigned int size = fifo->mask + 1;
unsigned int esize = fifo->esize;
unsigned int l;
off &= fifo->mask;
if (esize != 1) {
off *= esize;
size *= esize;
len *= esize;
}
l = min(len, size - off);
memcpy(fifo->data + off, src, l);
memcpy(fifo->data, src + l, len - l);
/*
* make sure that the data in the fifo is up to date before
* incrementing the fifo->in index counter
*/
smp_wmb();
}
unsigned int __kfifo_in(struct __kfifo *fifo,
const void *buf, unsigned int len)
{
unsigned int l;
l = kfifo_unused(fifo);
if (len > l)
len = l;
kfifo_copy_in(fifo, buf, len, fifo->in);
fifo->in += len;
return len;
}
EXPORT_SYMBOL(__kfifo_in);
static void kfifo_copy_out(struct __kfifo *fifo, void *dst,
unsigned int len, unsigned int off)
{
unsigned int size = fifo->mask + 1;
unsigned int esize = fifo->esize;
unsigned int l;
off &= fifo->mask;
if (esize != 1) {
off *= esize;
size *= esize;
len *= esize;
}
l = min(len, size - off);
memcpy(dst, fifo->data + off, l);
memcpy(dst + l, fifo->data, len - l);
/*
* make sure that the data is copied before
* incrementing the fifo->out index counter
*/
smp_wmb();
}
unsigned int __kfifo_out_peek(struct __kfifo *fifo,
void *buf, unsigned int len)
{
unsigned int l;
l = fifo->in - fifo->out;
if (len > l)
len = l;
kfifo_copy_out(fifo, buf, len, fifo->out);
return len;
}
EXPORT_SYMBOL(__kfifo_out_peek);
unsigned int __kfifo_out(struct __kfifo *fifo,
void *buf, unsigned int len)
{
len = __kfifo_out_peek(fifo, buf, len);
fifo->out += len;
return len;
}
EXPORT_SYMBOL(__kfifo_out);
static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
const void __user *from, unsigned int len, unsigned int off,
unsigned int *copied)
{
unsigned int size = fifo->mask + 1;
unsigned int esize = fifo->esize;
unsigned int l;
unsigned long ret;
off &= fifo->mask;
if (esize != 1) {
off *= esize;
size *= esize;
len *= esize;
}
l = min(len, size - off);
ret = copy_from_user(fifo->data + off, from, l);
if (unlikely(ret))
ret = DIV_ROUND_UP(ret + len - l, esize);
else {
ret = copy_from_user(fifo->data, from + l, len - l);
if (unlikely(ret))
ret = DIV_ROUND_UP(ret, esize);
}
/*
* make sure that the data in the fifo is up to date before
* incrementing the fifo->in index counter
*/
smp_wmb();
*copied = len - ret * esize;
/* return the number of elements which are not copied */
return ret;
}
int __kfifo_from_user(struct __kfifo *fifo, const void __user *from,
unsigned long len, unsigned int *copied)
{
unsigned int l;
unsigned long ret;
unsigned int esize = fifo->esize;
int err;
if (esize != 1)
len /= esize;
l = kfifo_unused(fifo);
if (len > l)
len = l;
ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied);
if (unlikely(ret)) {
len -= ret;
err = -EFAULT;
} else
err = 0;
fifo->in += len;
return err;
}
EXPORT_SYMBOL(__kfifo_from_user);
static unsigned long kfifo_copy_to_user(struct __kfifo *fifo, void __user *to,
unsigned int len, unsigned int off, unsigned int *copied)
{
unsigned int l;
unsigned long ret;
unsigned int size = fifo->mask + 1;
unsigned int esize = fifo->esize;
off &= fifo->mask;
if (esize != 1) {
off *= esize;
size *= esize;
len *= esize;
}
l = min(len, size - off);
ret = copy_to_user(to, fifo->data + off, l);
if (unlikely(ret))
ret = DIV_ROUND_UP(ret + len - l, esize);
else {
ret = copy_to_user(to + l, fifo->data, len - l);
if (unlikely(ret))
ret = DIV_ROUND_UP(ret, esize);
}
/*
* make sure that the data is copied before
* incrementing the fifo->out index counter
*/
smp_wmb();
*copied = len - ret * esize;
/* return the number of elements which are not copied */
return ret;
}
int __kfifo_to_user(struct __kfifo *fifo, void __user *to,
unsigned long len, unsigned int *copied)
{
unsigned int l;
unsigned long ret;
unsigned int esize = fifo->esize;
int err;
if (esize != 1)
len /= esize;
l = fifo->in - fifo->out;
if (len > l)
len = l;
ret = kfifo_copy_to_user(fifo, to, len, fifo->out, copied);
if (unlikely(ret)) {
len -= ret;
err = -EFAULT;
} else
err = 0;
fifo->out += len;
return err;
}
EXPORT_SYMBOL(__kfifo_to_user);
static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
int nents, unsigned int len)
{
int n;
unsigned int l;
unsigned int off;
struct page *page;
if (!nents)
return 0;
if (!len)
return 0;
n = 0;
page = virt_to_page(buf);
off = offset_in_page(buf);
l = 0;
while (len >= l + PAGE_SIZE - off) {
struct page *npage;
l += PAGE_SIZE;
buf += PAGE_SIZE;
npage = virt_to_page(buf);
if (page_to_phys(page) != page_to_phys(npage) - l) {
sg_set_page(sgl, page, l - off, off);
sgl = sg_next(sgl);
if (++n == nents || sgl == NULL)
return n;
page = npage;
len -= l - off;
l = off = 0;
}
}
sg_set_page(sgl, page, len, off);
return n + 1;
}
static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,
int nents, unsigned int len, unsigned int off)
{
unsigned int size = fifo->mask + 1;
unsigned int esize = fifo->esize;
unsigned int l;
unsigned int n;
off &= fifo->mask;
if (esize != 1) {
off *= esize;
size *= esize;
len *= esize;
}
l = min(len, size - off);
n = setup_sgl_buf(sgl, fifo->data + off, nents, l);
n += setup_sgl_buf(sgl + n, fifo->data, nents - n, len - l);
return n;
}
unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo,
struct scatterlist *sgl, int nents, unsigned int len)
{
unsigned int l;
l = kfifo_unused(fifo);
if (len > l)
len = l;
return setup_sgl(fifo, sgl, nents, len, fifo->in);
}
EXPORT_SYMBOL(__kfifo_dma_in_prepare);
unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo,
struct scatterlist *sgl, int nents, unsigned int len)
{
unsigned int l;
l = fifo->in - fifo->out;
if (len > l)
len = l;
return setup_sgl(fifo, sgl, nents, len, fifo->out);
}
EXPORT_SYMBOL(__kfifo_dma_out_prepare);
unsigned int __kfifo_max_r(unsigned int len, size_t recsize)
{
unsigned int max = (1 << (recsize << 3)) - 1;
if (len > max)
return max;
return len;
}
EXPORT_SYMBOL(__kfifo_max_r);
#define __KFIFO_PEEK(data, out, mask) \
((data)[(out) & (mask)])
/*
* __kfifo_peek_n internal helper function for determinate the length of
* the next record in the fifo
*/
static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize)
{
unsigned int l;
unsigned int mask = fifo->mask;
unsigned char *data = fifo->data;
l = __KFIFO_PEEK(data, fifo->out, mask);
if (--recsize)
l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8;
return l;
}
#define __KFIFO_POKE(data, in, mask, val) \
( \
(data)[(in) & (mask)] = (unsigned char)(val) \
)
/*
* __kfifo_poke_n internal helper function for storeing the length of
* the record into the fifo
*/
static void __kfifo_poke_n(struct __kfifo *fifo, unsigned int n, size_t recsize)
{
unsigned int mask = fifo->mask;
unsigned char *data = fifo->data;
__KFIFO_POKE(data, fifo->in, mask, n);
if (recsize > 1)
__KFIFO_POKE(data, fifo->in + 1, mask, n >> 8);
}
unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize)
{
return __kfifo_peek_n(fifo, recsize);
}
EXPORT_SYMBOL(__kfifo_len_r);
unsigned int __kfifo_in_r(struct __kfifo *fifo, const void *buf,
unsigned int len, size_t recsize)
{
if (len + recsize > kfifo_unused(fifo))
return 0;
__kfifo_poke_n(fifo, len, recsize);
kfifo_copy_in(fifo, buf, len, fifo->in + recsize);
fifo->in += len + recsize;
return len;
}
EXPORT_SYMBOL(__kfifo_in_r);
static unsigned int kfifo_out_copy_r(struct __kfifo *fifo,
void *buf, unsigned int len, size_t recsize, unsigned int *n)
{
*n = __kfifo_peek_n(fifo, recsize);
if (len > *n)
len = *n;
kfifo_copy_out(fifo, buf, len, fifo->out + recsize);
return len;
}
unsigned int __kfifo_out_peek_r(struct __kfifo *fifo, void *buf,
unsigned int len, size_t recsize)
{
unsigned int n;
if (fifo->in == fifo->out)
return 0;
return kfifo_out_copy_r(fifo, buf, len, recsize, &n);
}
EXPORT_SYMBOL(__kfifo_out_peek_r);
unsigned int __kfifo_out_r(struct __kfifo *fifo, void *buf,
unsigned int len, size_t recsize)
{
unsigned int n;
if (fifo->in == fifo->out)
return 0;
len = kfifo_out_copy_r(fifo, buf, len, recsize, &n);
fifo->out += n + recsize;
return len;
}
EXPORT_SYMBOL(__kfifo_out_r);
void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize)
{
unsigned int n;
n = __kfifo_peek_n(fifo, recsize);
fifo->out += n + recsize;
}
EXPORT_SYMBOL(__kfifo_skip_r);
int __kfifo_from_user_r(struct __kfifo *fifo, const void __user *from,
unsigned long len, unsigned int *copied, size_t recsize)
{
unsigned long ret;
len = __kfifo_max_r(len, recsize);
if (len + recsize > kfifo_unused(fifo)) {
*copied = 0;
return 0;
}
__kfifo_poke_n(fifo, len, recsize);
ret = kfifo_copy_from_user(fifo, from, len, fifo->in + recsize, copied);
if (unlikely(ret)) {
*copied = 0;
return -EFAULT;
}
fifo->in += len + recsize;
return 0;
}
EXPORT_SYMBOL(__kfifo_from_user_r);
int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to,
unsigned long len, unsigned int *copied, size_t recsize)
{
unsigned long ret;
unsigned int n;
if (fifo->in == fifo->out) {
*copied = 0;
return 0;
}
n = __kfifo_peek_n(fifo, recsize);
if (len > n)
len = n;
ret = kfifo_copy_to_user(fifo, to, len, fifo->out + recsize, copied);
if (unlikely(ret)) {
*copied = 0;
return -EFAULT;
}
fifo->out += n + recsize;
return 0;
}
EXPORT_SYMBOL(__kfifo_to_user_r);
unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo,
struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
{
BUG_ON(!nents);
len = __kfifo_max_r(len, recsize);
if (len + recsize > kfifo_unused(fifo))
return 0;
return setup_sgl(fifo, sgl, nents, len, fifo->in + recsize);
}
EXPORT_SYMBOL(__kfifo_dma_in_prepare_r);
void __kfifo_dma_in_finish_r(struct __kfifo *fifo,
unsigned int len, size_t recsize)
{
len = __kfifo_max_r(len, recsize);
__kfifo_poke_n(fifo, len, recsize);
fifo->in += len + recsize;
}
EXPORT_SYMBOL(__kfifo_dma_in_finish_r);
unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo,
struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
{
BUG_ON(!nents);
len = __kfifo_max_r(len, recsize);
if (len + recsize > fifo->in - fifo->out)
return 0;
return setup_sgl(fifo, sgl, nents, len, fifo->out + recsize);
}
EXPORT_SYMBOL(__kfifo_dma_out_prepare_r);
void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize)
{
unsigned int len;
len = __kfifo_peek_n(fifo, recsize);
fifo->out += len + recsize;
}
EXPORT_SYMBOL(__kfifo_dma_out_finish_r);
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