linux-kernel - [PATCH 2/2] ext4: refuse to create ea block when umounted

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Message-Id: <20221230110016.476621-2-jun.nie@linaro.org>
Date:   Fri, 30 Dec 2022 19:00:16 +0800
From:   Jun Nie <jun.nie@...aro.org>
To:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     tudor.ambarus@...aro.org
Subject: [PATCH 2/2] ext4: refuse to create ea block when umounted

The ea block expansion need to access s_root while it is
already set as NULL when umount is triggered. Refuse this
request to avoid panic.

Reported-by: syzbot+2dacb8f015bf1420155f@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=3613786cb88c93aa1c6a279b1df6a7b201347d08
Signed-off-by: Jun Nie <jun.nie@...aro.org>
---
 fs/ext4/xattr.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 235a517d9c17..ac58494e49b6 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1422,6 +1422,12 @@ static struct inode *ext4_xattr_inode_create(handle_t *handle,
 	uid_t owner[2] = { i_uid_read(inode), i_gid_read(inode) };
 	int err;
 
+	if (inode->i_sb->s_root == NULL) {
+		ext4_error(inode->i_sb,
+			   "refuse to create EA inode when umounting");
+		return ERR_PTR(-EINVAL);
+	}
+
 	/*
 	 * Let the next inode be the goal, so we try and allocate the EA inode
 	 * in the same group, or nearby one.
-- 
2.34.1