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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hulk Robot <hulkci@huawei.com>,
        Yang Yingliang <yangyingliang@huawei.com>,
        Theodore Tso <tytso@mit.edu>
Subject: [PATCH 5.12 052/700] ext4: return error code when ext4_fill_flex_info() fails
Date:   Mon, 12 Jul 2021 08:02:15 +0200
Message-Id: <20210712060932.050543519@linuxfoundation.org>
In-Reply-To: <20210712060924.797321836@linuxfoundation.org>
References: <20210712060924.797321836@linuxfoundation.org>
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From: Yang Yingliang <yangyingliang@huawei.com>

commit 8f6840c4fd1e7bd715e403074fb161c1a04cda73 upstream.

After commit c89128a00838 ("ext4: handle errors on
ext4_commit_super"), 'ret' may be set to 0 before calling
ext4_fill_flex_info(), if ext4_fill_flex_info() fails ext4_mount()
doesn't return error code, it makes 'root' is null which causes crash
in legacy_get_tree().

Fixes: c89128a00838 ("ext4: handle errors on ext4_commit_super")
Reported-by: Hulk Robot <hulkci@huawei.com>
Cc: <stable@vger.kernel.org> # v4.18+
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20210510111051.55650-1-yangyingliang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/super.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5039,6 +5039,7 @@ no_journal:
 			ext4_msg(sb, KERN_ERR,
 			       "unable to initialize "
 			       "flex_bg meta info!");
+			ret = -ENOMEM;
 			goto failed_mount6;
 		}