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Subject[PATCH] hfsplus: don't return 0 when fill_super() failed
From
Date
From f78a5fe168290cb9e009f4d907d04b5bfe277831 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Tue, 15 May 2018 11:38:38 +0900
Subject: [PATCH] hfsplus: don't return 0 when fill_super() failed

syzbot is reporting NULL pointer dereference at mount_fs() [1].
This is because hfsplus_fill_super() is by error returning 0 when
hfsplus_fill_super() detected invalid filesystem image, and mount_bdev()
is returning NULL because dget(s->s_root) == NULL if s->s_root == NULL,
and mount_fs() is accessing root->d_sb because IS_ERR(root) == false
if root == NULL. Fix this by returning -EINVAL when hfsplus_fill_super()
detected invalid filesystem image.

[1] https://syzkaller.appspot.com/bug?id=21acb6850cecbc960c927229e597158cf35f33d0

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+01ffaf5d9568dd1609f7@syzkaller.appspotmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
---
fs/hfsplus/super.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index 513c357..9e690ae 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -524,8 +524,10 @@ static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
goto out_put_root;
if (!hfs_brec_read(&fd, &entry, sizeof(entry))) {
hfs_find_exit(&fd);
- if (entry.type != cpu_to_be16(HFSPLUS_FOLDER))
+ if (entry.type != cpu_to_be16(HFSPLUS_FOLDER)) {
+ err = -EINVAL;
goto out_put_root;
+ }
inode = hfsplus_iget(sb, be32_to_cpu(entry.folder.id));
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
--
1.8.3.1

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