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From: "Ernesto A. Fernández" <ernesto.mnd.fernandez@gmail.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: ernesto.mnd.fernandez@gmail.com, akpm@linux-foundation.org,
	viro@zeniv.linux.org.uk, syzkaller-bugs@googlegroups.com,
	syzbot+01ffaf5d9568dd1609f7@syzkaller.appspotmail.com,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] hfsplus: don't return 0 when fill_super() failed
Date: Sat, 19 May 2018 20:25:04 -0300	[thread overview]
Message-ID: <20180519232503.oya6winh6fvxlh7t@eaf> (raw)
In-Reply-To: <201805192255.CAD48427.HLtFMOFVOSOQJF@I-love.SAKURA.ne.jp>

On Sat, May 19, 2018 at 10:55:04PM +0900, Tetsuo Handa wrote:
> Ernesto A. Fernandez wrote:
> > On Tue, May 15, 2018 at 07:08:24PM +0900, Tetsuo Handa wrote:
> > > 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
> > > 
> > > 
> > 
> > I sent this same patch some time ago:
> > 
> > https://www.spinics.net/lists/linux-fsdevel/msg125241.html
> > 
> > This syzbot report did not reach me, though. I don't know why.
> > 
> Oh, I didn't notice that you already wrote that patch.
> Anyway, whom to ask for merge? Al Viro? Andrew Morton?

I think Andrew Morton, but only one of my patches for hfsplus has been
picked up so far, so I can't tell you for sure.

Al Viro wasn't happy with this patchset and thought it was better to let
->put_super() handle the cleanup. I made a second version but I don't
think he had the time to look at it yet.

  parent reply	other threads:[~2018-05-19 23:25 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-05  2:02 general protection fault in mount_fs syzbot
2018-05-15 10:08 ` [PATCH] hfsplus: don't return 0 when fill_super() failed Tetsuo Handa
     [not found]   ` <20180515164221.57cbosgvu6ahslon@eaf>
     [not found]     ` <201805192255.CAD48427.HLtFMOFVOSOQJF@I-love.SAKURA.ne.jp>
2018-05-19 23:25       ` Ernesto A. Fernández [this message]
2018-05-19 23:47         ` Al Viro
2018-06-21  1:45   ` Ernesto A. Fernández

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