fs: prevent page refcount overflow in pipe_buf_get
Change pipe_buf_get() to return a bool indicating whether it succeeded in raising the refcount of the page (if the thing in the pipe is a page). This removes another mechanism for overflowing the page refcount. All callers converted to handle a failure. Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Matthew Wilcox <willy@infradead.org> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -2034,10 +2034,8 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
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rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;
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ret = -EINVAL;
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if (rem < len) {
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pipe_unlock(pipe);
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goto out;
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}
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if (rem < len)
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goto out_free;
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rem = len;
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while (rem) {
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@ -2055,7 +2053,9 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
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pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
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pipe->nrbufs--;
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} else {
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pipe_buf_get(pipe, ibuf);
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if (!pipe_buf_get(pipe, ibuf))
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goto out_free;
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*obuf = *ibuf;
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obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
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obuf->len = rem;
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@ -2078,11 +2078,11 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
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ret = fuse_dev_do_write(fud, &cs, len);
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pipe_lock(pipe);
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out_free:
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for (idx = 0; idx < nbuf; idx++)
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pipe_buf_release(pipe, &bufs[idx]);
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pipe_unlock(pipe);
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out:
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kvfree(bufs);
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return ret;
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}
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@ -189,9 +189,9 @@ EXPORT_SYMBOL(generic_pipe_buf_steal);
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* in the tee() system call, when we duplicate the buffers in one
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* pipe into another.
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*/
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void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
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bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
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{
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get_page(buf->page);
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return try_get_page(buf->page);
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}
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EXPORT_SYMBOL(generic_pipe_buf_get);
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12
fs/splice.c
12
fs/splice.c
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@ -1588,7 +1588,11 @@ retry:
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* Get a reference to this pipe buffer,
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* so we can copy the contents over.
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*/
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pipe_buf_get(ipipe, ibuf);
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if (!pipe_buf_get(ipipe, ibuf)) {
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if (ret == 0)
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ret = -EFAULT;
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break;
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}
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*obuf = *ibuf;
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/*
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@ -1660,7 +1664,11 @@ static int link_pipe(struct pipe_inode_info *ipipe,
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* Get a reference to this pipe buffer,
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* so we can copy the contents over.
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*/
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pipe_buf_get(ipipe, ibuf);
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if (!pipe_buf_get(ipipe, ibuf)) {
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if (ret == 0)
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ret = -EFAULT;
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break;
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}
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obuf = opipe->bufs + nbuf;
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*obuf = *ibuf;
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@ -108,18 +108,20 @@ struct pipe_buf_operations {
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/*
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* Get a reference to the pipe buffer.
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*/
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void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
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bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
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};
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/**
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* pipe_buf_get - get a reference to a pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to get a reference to
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*
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* Return: %true if the reference was successfully obtained.
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*/
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static inline void pipe_buf_get(struct pipe_inode_info *pipe,
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static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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buf->ops->get(pipe, buf);
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return buf->ops->get(pipe, buf);
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}
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/**
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@ -178,7 +180,7 @@ struct pipe_inode_info *alloc_pipe_info(void);
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void free_pipe_info(struct pipe_inode_info *);
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/* Generic pipe buffer ops functions */
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void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
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bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
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void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
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@ -6835,12 +6835,16 @@ static void buffer_pipe_buf_release(struct pipe_inode_info *pipe,
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buf->private = 0;
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}
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static void buffer_pipe_buf_get(struct pipe_inode_info *pipe,
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static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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struct buffer_ref *ref = (struct buffer_ref *)buf->private;
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if (ref->ref > INT_MAX/2)
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return false;
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ref->ref++;
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return true;
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}
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/* Pipe buffer operations for a buffer. */
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