[PATCH 4.19 021/421] ext4: return error code when ext4_fill_flex_info() fails

From: Greg Kroah-Hartman
Date: Mon Jul 19 2021 - 11:47:08 EST

From: Yang Yingliang <yangyingliang@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.18+
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210510111051.55650-1-yangyingliang@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4524,6 +4524,7 @@ no_journal:
ext4_msg(sb, KERN_ERR,
"unable to initialize "
"flex_bg meta info!");
+ ret = -ENOMEM;
goto failed_mount6;