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mm/filemap: fix infinite loop in generic_file_buffered_read() 

commit 3644e2d2dd upstream.

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>
Signed-off-by: Suraj Jitindar Singh <surajjs@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kent Overstreet 2020-12-18 04:07:11 -05:00 committed by Greg Kroah-Hartman
parent 0c5d5f8e0d
commit 2cdcf6481c
1 changed files with 3 additions and 0 deletions
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3
mm/filemap.c
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@ -2203,6 +2203,9 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
return 0;
if (unlikely(!iov_iter_count(iter)))
return 0;
iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
index = *ppos >> PAGE_SHIFT;