linux-kernel - Re: [PATCH 44/64] cachefiles: Implement key to filename encoding

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Message-ID: <571668.1638347365@warthog.procyon.org.uk>
Date:   Wed, 01 Dec 2021 08:29:25 +0000
From:   David Howells <dhowells@...hat.com>
To:     JeffleXu <jefflexu@...ux.alibaba.com>
Cc:     dhowells@...hat.com, linux-cachefs@...hat.com,
        Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <sfrench@...ba.org>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Jeff Layton <jlayton@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Omar Sandoval <osandov@...ndov.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
        linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 44/64] cachefiles: Implement key to filename encoding

JeffleXu <jefflexu@...ux.alibaba.com> wrote:

> > +	/* If the path is usable ASCII, then we render it directly */
> > +	if (print) {
> > +		len = 1 + keylen + 1;
> > +		name = kmalloc(len, GFP_KERNEL);
> > +		if (!name)
> > +			return false;
> > +
> > +		name[0] = 'D'; /* Data object type, string encoding */
> > +		name[1 + keylen] = 0;
> > +		memcpy(name + 1, key, keylen);
> > +		goto success;
> 			^
> If we goto success from here,
> ...
> > +
> > +success:
> > +	name[len] = 0;
> 	     ^
> then it seems that this will cause an out-of-boundary access.

You're right.  I'll change that to:

		len = 1 + keylen;
		name = kmalloc(len + 1, GFP_KERNEL);

and I shouldn't need:

		name[1 + keylen] = 0;

as that's also done after the success label.

David