From 36e2c7421f02a22f71c9283e55fdb672a9eb58e7 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 3 Sep 2020 16:22:34 +0200 Subject: fs: don't allow splice read/write without explicit ops 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 Reviewed-by: Kees Cook Signed-off-by: Al Viro --- fs/splice.c | 130 +++++++----------------------------------------------------- 1 file changed, 14 insertions(+), 116 deletions(-) (limited to 'fs/splice.c') diff --git a/fs/splice.c b/fs/splice.c index d7c8a7c4db07..412df7b48f9e 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -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 @@ done: 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) - return out->f_op->splice_write(pipe, out, ppos, len, flags); - return default_file_splice_write(pipe, out, ppos, len, flags); + if (unlikely(!out->f_op->splice_write)) + return warn_unsupported(out, "write"); + return out->f_op->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) - return in->f_op->splice_read(in, ppos, pipe, len, flags); - return default_file_splice_read(in, ppos, pipe, len, flags); + if (unlikely(!in->f_op->splice_read)) + return warn_unsupported(in, "read"); + return in->f_op->splice_read(in, ppos, pipe, len, flags); } /** -- cgit v1.2.3-59-g8ed1b