mm/filemap: fix infinite loop in generic_file_buffered_read()
authorKent Overstreet <kent.overstreet@gmail.com>
Fri, 18 Dec 2020 09:07:11 +0000 (04:07 -0500)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 18 Dec 2020 21:37:04 +0000 (13:37 -0800)
commit3644e2d2dda78e21edd8f5415b6d7ab03f5f54f3
treee9474ee78d90927d36cd1b730d0df405953afde9
parenta0b96314870f7eff6d15a242cb162dfc46b3c284
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>
mm/filemap.c