From nobody Tue Dec 16 15:45:11 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B153A27CB0B; Tue, 6 May 2025 11:56:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746532563; cv=none; b=ruErTGMDE7BjX16NCnotWFKy6rCYKiW4uAUWq+TsTzha3O8sZXRQGgg36nMo+PSb1dQWBsCFa3Nt+OHSdYOHF/zUrtZmJMMh9PZwRtYpP2qrWJCPnnzLBpXOA5RxuW67KVa+RXLQs9CxUOpB6WEfUZ3/ORD/EQZU3LmY89/QPyQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746532563; c=relaxed/simple; bh=wkLpQXzGAXHdGAr38No8C2VE5KifFLlLwwTCYQNol9c=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=VLboNMEYJVw5r9xcO+5pDPm5XU3gl9sZk8WaKUYpwlLOClPjXA0nay9f2/eghvoCbp3JSb6R2HBjXpykhMFFJ6SQpXKtgt6vo/bXizybjt5NrEQo4e8JIE7h3I9Dis9sVbJdqqBOiWo5tEtEQ4yfSZ70aD+HtZla9Jd9I0d0QkY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mEP27UP/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mEP27UP/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04EEDC4CEE4; Tue, 6 May 2025 11:56:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746532563; bh=wkLpQXzGAXHdGAr38No8C2VE5KifFLlLwwTCYQNol9c=; h=From:To:Cc:Subject:Date:From; b=mEP27UP/BmEkNHYglu7YbuBNHWL2kWeo8vvpmlKR0Z/fnee4BcMP76ULSI2xHQ1d5 muCKs/Jb/UtWoMzf273qi1fDnmgjNerKXIKvwftb0PpJ4pjDoy/bdbGGiLL/fcIm+n YLkunHArPgJoOj4+iw8pZIVd2VQeNwvbRfS+WP6gcMHHBUr0rrxYzbMwJHHxKn6sZP GlR4FtFYnWQEViG3RkGkczLtqVuCVZ9GWPyzGqAUnDi0fpy7GbvdL8zhdFyPtNLWKl IXJk5ouAqjD3gBFd4gBoFNmhCrM5hfqz2uC8lQRUSver+gtROOQeSTW8XEjH7Wcdkw kupm3KAKHmg1A== From: Christian Brauner To: Oleg Nesterov Cc: Christian Brauner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] pidfs: detect refcount bugs Date: Tue, 6 May 2025 13:55:54 +0200 Message-ID: <20250506-uferbereich-guttun-7c8b1a0a431f@brauner> X-Mailer: git-send-email 2.47.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=811; i=brauner@kernel.org; h=from:subject:message-id; bh=wkLpQXzGAXHdGAr38No8C2VE5KifFLlLwwTCYQNol9c=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWRI/jgtsMHb7dqvroSS49NnJCy9XnjtUyjLe7/YVJ3LK 4RfsYXFdZSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAEwkQI2R4X2vQV5c+44IiayN yx4w/V5zddpilUKFdRO2TpE5sHnpNkuGP/xm+/s01u9TqXsW0Vp0v9uC8cm7S2W/VbO01n87e0h jNTcA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Now that we have pidfs_{get,register}_pid() that needs to be paired with pidfs_put_pid() it's possible that someone pairs them with put_pid(). Thus freeing struct pid while it's still used by pidfs. Notice when that happens. I'll also add a scheme to detect invalid uses of pidfs_get_pid() and pidfs_put_pid() later. Signed-off-by: Christian Brauner --- kernel/pid.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/pid.c b/kernel/pid.c index 26f1e136f017..8317bcbc7cf7 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -100,6 +100,7 @@ void put_pid(struct pid *pid) =20 ns =3D pid->numbers[pid->level].ns; if (refcount_dec_and_test(&pid->count)) { + WARN_ON_ONCE(pid->stashed); kmem_cache_free(ns->pid_cachep, pid); put_pid_ns(ns); } --=20 2.47.2