From: Breno Leitao <leitao@debian.org>
To: Joshua Crofts <joshua.crofts1@gmail.com>
Cc: Andreas Hindborg <a.hindborg@kernel.org>,
linux-kernel@vger.kernel.org,
syzbot+35790eb7861f8fc57382@syzkaller.appspotmail.com
Subject: Re: [PATCH] configfs: fix refcount warning in configfs_get_config_item()
Date: Wed, 29 Jul 2026 03:06:09 -0700 [thread overview]
Message-ID: <amnP4PTUHSfQqk3h@gmail.com> (raw)
In-Reply-To: <20260729085505.1316-1-joshua.crofts1@gmail.com>
On Wed, Jul 29, 2026 at 08:55:05AM +0000, Joshua Crofts wrote:
> syzbot reported a "refcount_t: addition on 0; use-after-free" warning
> in configfs_get_config_item().
>
> This occurs when configfs_get_config_item() races with a concurrent
> teardown (e.g. rmdir). When the target config_item's refcount drops to
> 0, configfs_get_config_item() calls config_item_get(), which
> unconditionally increments the refcount via kref_get(), triggering the
> refcount warning.
Shouldn't be this the fix we are interested in fixing?
> Fix this by using config_item_get_unless_zero(), which safely returns
> NULL if the refcount is already 0.
This looks like more a workaround than a proper fix, no?
I got the impression that we have a UAF behind this refcount issue, and
this is not being solved by this patch.
next prev parent reply other threads:[~2026-07-29 10:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-29 8:55 [PATCH] configfs: fix refcount warning in configfs_get_config_item() Joshua Crofts
2026-07-29 9:00 ` Joshua Crofts
2026-07-29 9:51 ` Jeffin Philip
2026-07-29 13:50 ` Joshua Crofts
2026-07-29 10:06 ` Breno Leitao [this message]
2026-07-29 13:31 ` Joshua Crofts
2026-07-29 15:05 ` Jeffin Philip
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