4.9-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=21acb6850cecbc960c927229e597158cf35f33d...
Link: http://lkml.kernel.org/r/d83ce31a-874c-dd5b-f790-41405983a5be@I-love.SAKURA.... 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);