From mboxrd@z Thu Jan 1 00:00:00 1970 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 3959C36A00D; Thu, 13 Nov 2025 16:38:47 +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=1763051927; cv=none; b=POSnFparI1mLNCjisjF5WYkbrMtK8cCxjB6K4KBxLcam/eTWsCZrNC43T3nl9v+jnK91byk3JdNuklSbsS9WI0dGgo/GkNXerZPJBgNBuTvmg4lgSuxOkRfvG2Fkoa31ijl298mbwgXNhNluvXtJWhXH/YP2kec67P529MCgUOQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763051927; c=relaxed/simple; bh=hJii1S5TPrgsZOcgVV0ADZVBuDyGKXP9zHQY6mXDctw=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=VDMw7qE6FbFUb0R5y9JVMMBfz8XBb82jdfI2+eO1kWmBwuvEzM/eycnDtKmMe28HcvkBKZ8Iwii4XInaoAt4ZbcKRSSGV4bvs6kY69d3TrliMi7lbDkjArKYkGBYrE7YR2LN7mU7uZJGti7DpqrNCG8mevHs5w4+b2rd/DOMcUc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fgC3fE8e; 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="fgC3fE8e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B24FEC4CEF1; Thu, 13 Nov 2025 16:38:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763051927; bh=hJii1S5TPrgsZOcgVV0ADZVBuDyGKXP9zHQY6mXDctw=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=fgC3fE8ekAGH44qW3L0tVOYLSXROaWXGK+albypMjnDU/oXOn43/4bSV/BPCWIyfZ 10kcskrsbk6GS9wGAIvVQq1Ni1s8mB8ek45lOfRwrgM82bCbkDRo3GtEB0Rv2vpyf7 PcmK1LnElOEK0VZqZPnXtowaD4sh4ACv5Nagx7ET8Qm0ARHfWMvCzRufE5dbcyknAB 0+vh7QNjWpZF5xqOBCLBxaQbcVWys0buaUMLJWnY5IvjexyNVaI5VAK2TL/5AJxJ2c QyL9D5Uxx1XKh+ruAFizUcjcQhDjt6t515c1U3SujQjH1MioL1sWyyhxvIMtYifJN4 jGfVKDv65dzWw== From: Christian Brauner Date: Thu, 13 Nov 2025 17:37:47 +0100 Subject: [PATCH v2 42/42] ovl: detect double credential overrides Precedence: bulk X-Mailing-List: linux-unionfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251113-work-ovl-cred-guard-v2-42-c08940095e90@kernel.org> References: <20251113-work-ovl-cred-guard-v2-0-c08940095e90@kernel.org> In-Reply-To: <20251113-work-ovl-cred-guard-v2-0-c08940095e90@kernel.org> To: Miklos Szeredi , Amir Goldstein Cc: Linus Torvalds , linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christian Brauner X-Mailer: b4 0.15-dev-a6db3 X-Developer-Signature: v=1; a=openpgp-sha256; l=828; i=brauner@kernel.org; h=from:subject:message-id; bh=hJii1S5TPrgsZOcgVV0ADZVBuDyGKXP9zHQY6mXDctw=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWSKcXoUdCzs01uYFPrXLZUxXU1OKlbPb94euY+x0xZay 8snV2V0lLIwiHExyIopsji0m4TLLeep2GyUqQEzh5UJZAgDF6cATOR0OsP/cBGfzhXGVzWMzK5N aotmPHOjXmptY0XJVsbN9xbW7bb4ychw66fSwaB5h/f/WZZ7eZ+7Dcfu+ItzW602lhiuVUlKPSL LAAA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Overlayfs always allocates a private copy for ofs->creator_creds. So there is never going to be a task that uses ofs->creator_creds. This means we can use an vfs debug assert to detect accidental double credential overrides. Signed-off-by: Christian Brauner --- fs/overlayfs/util.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index dc521f53d7a3..f41b9d825a0f 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -66,6 +66,8 @@ const struct cred *ovl_override_creds(struct super_block *sb) { struct ovl_fs *ofs = OVL_FS(sb); + /* Detect callchains where we override credentials multiple times. */ + VFS_WARN_ON_ONCE(current->cred == ofs->creator_cred); return override_creds(ofs->creator_cred); } -- 2.47.3