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fs: don't allow splice read/write without explicit ops

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default_file_splice_write is the last piece of generic code that uses
set_fs to make the uaccess routines operate on kernel pointers.  It
implements a "fallback loop" for splicing from files that do not actually
provide a proper splice_read method.  The usual file systems and other
high bandwidth instances all provide a ->splice_read, so this just removes
support for various device drivers and procfs/debugfs files.  If splice
support for any of those turns out to be important it can be added back
by switching them to the iter ops and using generic_file_splice_read.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2020-09-03 16:22:34 +02:00 committed by Al Viro
parent 4d03e3cc59
commit 36e2c7421f
3 changed files with 15 additions and 119 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
fs/read_write.c
View file

@ -1077,7 +1077,7 @@ ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
}
EXPORT_SYMBOL(vfs_iter_write);
ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
static ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
unsigned long vlen, loff_t *pos, rwf_t flags)
{
struct iovec iovstack[UIO_FASTIOV];

126
fs/splice.c
View file

@ -342,89 +342,6 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = {
};
EXPORT_SYMBOL(nosteal_pipe_buf_ops);
static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
unsigned long vlen, loff_t offset)
{
mm_segment_t old_fs;
loff_t pos = offset;
ssize_t res;
old_fs = get_fs();
set_fs(KERNEL_DS);
/* The cast to a user pointer is valid due to the set_fs() */
res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
set_fs(old_fs);
return res;
}
static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
struct iov_iter to;
struct page **pages;
unsigned int nr_pages;
unsigned int mask;
size_t offset, base, copied = 0;
ssize_t res;
int i;
if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
return -EAGAIN;
/*
* Try to keep page boundaries matching to source pagecache ones -
* it probably won't be much help, but...
*/
offset = *ppos & ~PAGE_MASK;
iov_iter_pipe(&to, READ, pipe, len + offset);
res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
if (res <= 0)
return -ENOMEM;
nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
vec = __vec;
if (nr_pages > PIPE_DEF_BUFFERS) {
vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
if (unlikely(!vec)) {
res = -ENOMEM;
goto out;
}
}
mask = pipe->ring_size - 1;
pipe->bufs[to.head & mask].offset = offset;
pipe->bufs[to.head & mask].len -= offset;
for (i = 0; i < nr_pages; i++) {
size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
vec[i].iov_base = page_address(pages[i]) + offset;
vec[i].iov_len = this_len;
len -= this_len;
offset = 0;
}
res = kernel_readv(in, vec, nr_pages, *ppos);
if (res > 0) {
copied = res;
*ppos += res;
}
if (vec != __vec)
kfree(vec);
out:
for (i = 0; i < nr_pages; i++)
put_page(pages[i]);
kvfree(pages);
iov_iter_advance(&to, copied); /* truncates and discards */
return res;
}
/*
* Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
* using sendpage(). Return the number of bytes sent.
@ -788,33 +705,6 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
EXPORT_SYMBOL(iter_file_splice_write);
static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{
int ret;
void *data;
loff_t tmp = sd->pos;
data = kmap(buf->page);
ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
kunmap(buf->page);
return ret;
}
static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
struct file *out, loff_t *ppos,
size_t len, unsigned int flags)
{
ssize_t ret;
ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
if (ret > 0)
*ppos += ret;
return ret;
}
/**
* generic_splice_sendpage - splice data from a pipe to a socket
* @pipe: pipe to splice from
@ -836,15 +726,23 @@ ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
EXPORT_SYMBOL(generic_splice_sendpage);
static int warn_unsupported(struct file *file, const char *op)
{
pr_debug_ratelimited(
"splice %s not supported for file %pD4 (pid: %d comm: %.20s)\n",
op, file, current->pid, current->comm);
return -EINVAL;
}
/*
* Attempt to initiate a splice from pipe to file.
*/
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
if (out->f_op->splice_write)
if (unlikely(!out->f_op->splice_write))
return warn_unsupported(out, "write");
return out->f_op->splice_write(pipe, out, ppos, len, flags);
return default_file_splice_write(pipe, out, ppos, len, flags);
}
/*
@ -866,9 +764,9 @@ static long do_splice_to(struct file *in, loff_t *ppos,
if (unlikely(len > MAX_RW_COUNT))
len = MAX_RW_COUNT;
if (in->f_op->splice_read)
if (unlikely(!in->f_op->splice_read))
return warn_unsupported(in, "read");
return in->f_op->splice_read(in, ppos, pipe, len, flags);
return default_file_splice_read(in, ppos, pipe, len, flags);
}
/**

2
include/linux/fs.h
View file

@ -1894,8 +1894,6 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
unsigned long, loff_t *, rwf_t);
extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
loff_t, size_t, unsigned int);
extern ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,