From: Kent Overstreet Date: Fri, 18 Dec 2020 09:07:11 +0000 (-0500) Subject: mm/filemap: fix infinite loop in generic_file_buffered_read() X-Git-Tag: v5.11-rc1~62 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=3644e2d2dda78e21edd8f5415b6d7ab03f5f54f3;p=linux-2.6-block.git 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 Reported-by: Jens Axboe Reviewed-by: Jens Axboe Signed-off-by: Linus Torvalds --- diff --git a/mm/filemap.c b/mm/filemap.c index 7a49bac48aea..5c9d564317a5 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -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))