From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: viro@ZenIV.linux.org.uk
Cc: linux-fsdevel@vger.kernel.org
Subject: Re: fs: Uninitialized memory read at take_dentry_name_snapshot
Date: Mon, 4 Sep 2017 23:11:04 +0900 [thread overview]
Message-ID: <201709042311.IIE60447.OJSQFMHtOFLVOF@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20170904132106.GU5426@ZenIV.linux.org.uk>
Al Viro wrote:
> On Mon, Sep 04, 2017 at 09:12:38PM +0900, Tetsuo Handa wrote:
> > Hello.
> >
> > I hit kmemcheck splat on commit 49d31c2f389acfe8 ("dentry name snapshots") using linux-next-20170901.
> > Changing to strncpy() fixes this problem, but using strncpy() only if CONFIG_KMEMCHECK=y is better
> > for performance?
>
> *shrug*
>
> If anything, use dentry->d_name.len + 1 instead of DNAME_INLINE_LEN there, but
> that's really a false positive.
A false positive? Isn't it because we do
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
(...snipped...)
dname = dentry->d_iname;
(...snipped...)
memcpy(dname, name->name, name->len);
dname[name->len] = 0;
at __d_alloc() which leaves a room for some of d_iname[] bytes uninitialized?
So, I think either pad explicitly at __f_alloc() or use dentry->d_name.len + 1 is needed.
next prev parent reply other threads:[~2017-09-04 14:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-04 12:12 fs: Uninitialized memory read at take_dentry_name_snapshot Tetsuo Handa
2017-09-04 13:21 ` Al Viro
2017-09-04 14:11 ` Tetsuo Handa [this message]
2017-09-04 14:22 ` Al Viro
2017-09-04 16:56 ` Vegard Nossum
2017-09-13 10:12 ` [PATCH] dentry: Fix kmemcheck splat at take_dentry_name_snapshot() Tetsuo Handa
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