linux-ext4 - [PATCH 1/2] ext4: Fixes len calculation in mpage_journal_page

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Date: Thu, 29 Feb 2024 11:40:13 +0530
From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To: linux-ext4@...r.kernel.org
Cc: Jan Kara <jack@...e.cz>,
	"Ritesh Harjani (IBM)" <ritesh.list@...il.com>,
	stable@...nel.org
Subject: [PATCH 1/2] ext4: Fixes len calculation in mpage_journal_page_buffers

Truncate operation can race with writeback, in which inode->i_size can get
truncated and therefore size - folio_pos() can be negative. This fixes the
len calculation. However this path doesn't get easily triggered even
with data journaling.

Cc:  <stable@...nel.org> # v6.5
Fixes: 80be8c5cc925 ("Fixes: ext4: Make mpage_journal_page_buffers use folio")
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---
 fs/ext4/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 537803250ca9..bab9223d94ac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2334,7 +2334,7 @@ static int mpage_journal_page_buffers(handle_t *handle,
 
 	if (folio_pos(folio) + len > size &&
 	    !ext4_verity_in_progress(inode))
-		len = size - folio_pos(folio);
+		len = size & (len - 1);
 
 	return ext4_journal_folio_buffers(handle, folio, len);
 }
-- 
2.39.2