linux-kernel - Re: [git pull] mount API series

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Message-ID: <20181102194235.GA32577@ZenIV.linux.org.uk>
Date:   Fri, 2 Nov 2018 19:42:35 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Gao Xiang <gaoxiang25@...wei.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        swhiteho@...hat.com, john.johansen@...onical.com,
        alan.christopher.jenkins@...il.com, ebiederm@...hat.com,
        linux-fsdevel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] mount API series

On Fri, Nov 02, 2018 at 04:07:01AM +0000, Al Viro wrote:
> On Thu, Nov 01, 2018 at 11:59:23PM +0000, David Howells wrote:
> 
> >  (*) mount-api-core.  These are the internal-only patches that add the
> >      fs_context, the legacy wrapper and the security hooks and make certain
> >      filesystems make use of it.
> 
> FWIW, while rereading that series I'd spotted something very odd in erofs.
> It's orthogonal to everything else, but just to make sure it doesn't get
> lost:
> 	* sbi->dev_name thing in erofs is used only for debugging printks,
> basically.  Just use sb->s_id[] and be done with that.
> 	* dump struct erofs_mount_private - you don't need dev_name in
> your erofs_fill_super().  Just use mount_bdev() in usual fashion.
> 	* what the hell are you doing with ->s_root???  Why would you
> possibly want it hashed and what kind of dcache lookup could find it?
> That d_rehash() looks deeply confused; what are you trying to do there?

... and while we are at it, what happens to
                unsigned int nameoff = le16_to_cpu(de[mid].nameoff);
                unsigned int matched = min(startprfx, endprfx);

                struct qstr dname = QSTR_INIT(data + nameoff,
                        unlikely(mid >= ndirents - 1) ?
                                maxsize - nameoff :
                                le16_to_cpu(de[mid + 1].nameoff) - nameoff);

                /* string comparison without already matched prefix */
                int ret = dirnamecmp(name, &dname, &matched);
if le16_to_cpu(de[...].nameoff) is not monotonically increasing?  I.e.
what's to prevent e.g. (unsigned)-1 ending up in dname.len?

Corrupted fs image shouldn't oops the kernel...