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    Subject[PATCH 4.18 038/197] hfsplus: dont return 0 when fill_super() failed
    Date
    4.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

    [ Upstream commit 7464726cb5998846306ed0a7d6714afb2e37b25d ]

    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

    Link: http://lkml.kernel.org/r/d83ce31a-874c-dd5b-f790-41405983a5be@I-love.SAKURA.ne.jp
    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Reported-by: syzbot <syzbot+01ffaf5d9568dd1609f7@syzkaller.appspotmail.com>
    Reviewed-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
    Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/hfsplus/super.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/fs/hfsplus/super.c
    +++ b/fs/hfsplus/super.c
    @@ -524,8 +524,10 @@ static int hfsplus_fill_super(struct sup
    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);

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