linux-ext4 - [PATCH] ext4: Fix the issue of missing lock in ext4_page

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Message-Id: <20250330075515.37699-1-superman.xpt@gmail.com>
Date: Sun, 30 Mar 2025 00:55:15 -0700
From: Penglei Jiang <superman.xpt@...il.com>
To: tytso@....edu,
	adilger.kernel@...ger.ca
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.or,
	syzbot+d14b2bea87fe2aaffa3b@...kaller.appspotmail.com,
	Penglei Jiang <superman.xpt@...il.com>
Subject: [PATCH] ext4: Fix the issue of missing lock in ext4_page_mkwrite

In ext4_page_mkwrite, it calls ext4_convert_inline_data, but it does
not use inode_lock to hold i_rwsem.

Fixes: 7b4cc9787fe35 ("ext4: evict inline data when writing to memory map")
Reported-by: syzbot+d14b2bea87fe2aaffa3b@...kaller.appspotmail.com
Closes: https://lore.kernel.org/all/67e57c6c.050a0220.2f068f.0037.GAE@google.com
Signed-off-by: Penglei Jiang <superman.xpt@...il.com>
---
 fs/ext4/inode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bcb96caf77c0..4e726c86377a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -6203,6 +6203,8 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
 	sb_start_pagefault(inode->i_sb);
 	file_update_time(vma->vm_file);
 
+	inode_lock(inode);
+
 	filemap_invalidate_lock_shared(mapping);
 
 	err = ext4_convert_inline_data(inode);
@@ -6308,6 +6310,7 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
 	ret = vmf_fs_error(err);
 out:
 	filemap_invalidate_unlock_shared(mapping);
+	inode_unlock(inode);
 	sb_end_pagefault(inode->i_sb);
 	return ret;
 out_error:
-- 
2.17.1