Commit 3644e2d2 authored Dec 18, 2020 by Kent Overstreet Committed by Linus Torvalds Dec 18, 2020

mm/filemap: fix infinite loop in generic_file_buffered_read()



If iter->count is 0 and iocb->ki_pos is page aligned, this causes
nr_pages to be 0.

Then in generic_file_buffered_read_get_pages() find_get_pages_contig()
returns 0 - because we asked for 0 pages, so we call
generic_file_buffered_read_no_cached_page() which attempts to add a page
to the page cache, which fails with -EEXIST, and then we loop. Oops...

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Reported-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a0b96314

mm/filemap.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2453,6 +2453,9 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,

		if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
		return 0;
		if (unlikely(!iov_iter_count(iter)))
		return 0;

		iov_iter_truncate(iter, inode->i_sb->s_maxbytes);

		if (nr_pages > ARRAY_SIZE(pages_onstack))

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