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Message-ID: <20230919232815.166772-1-surajjs@amazon.com>
Date: Tue, 19 Sep 2023 16:28:15 -0700
From: Suraj Jitindar Singh <surajjs@...zon.com>
To: <stable@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
<kent.overstreet@...il.com>, <axboe@...nel.dk>,
<sjitindarsingh@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Suraj Jitindar Singh <surajjs@...zon.com>
Subject: [PATCH stable 5.10.y] mm/filemap: fix infinite loop in generic_file_buffered_read()
From: Kent Overstreet <kent.overstreet@...il.com>
commit 3644e2d2dda78e21edd8f5415b6d7ab03f5f54f3 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@...il.com>
Reported-by: Jens Axboe <axboe@...nel.dk>
Reviewed-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Suraj Jitindar Singh <surajjs@...zon.com>
---
mm/filemap.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/filemap.c b/mm/filemap.c
index 3a983bc1a71c..3b0d8c6dd587 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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;
--
2.34.1
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