Commit 3993382b authored Nov 11, 2020 by Miklos Szeredi

fuse: launder page should wait for page writeback



Qian Cai reports that the WARNING in tree_insert() can be triggered by a
fuzzer with the following call chain:

invalidate_inode_pages2_range()
   fuse_launder_page()
      fuse_writepage_locked()
         tree_insert()

The reason is that another write for the same page is already queued.

The simplest fix is to wait until the pending write is completed and only
after that queue the new write.

Since this case is very rare, the additional wait should not be a problem.

Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

parent 3650b228

fs/fuse/file.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2281,6 +2281,9 @@ static int fuse_launder_page(struct page *page)
		int err = 0;
		if (clear_page_dirty_for_io(page)) {
		struct inode *inode = page->mapping->host;

		/* Serialize with pending writeback for the same page */
		fuse_wait_on_page_writeback(inode, page->index);
		err = fuse_writepage_locked(page);
		if (!err)
		fuse_wait_on_page_writeback(inode, page->index);

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