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 9CEB044369 for ; Wed, 13 Mar 2024 14:02:05 +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=1710338525; cv=none; b=gkNrSve3NznUi7VnaK0tivMlMPb6Rj805TUJJ6eaIOqEDbbJFSRQR/YuL0AAlbn/qBXKWVa3Y+b55/OUei8KBTqcajZ5gqzyz15g27vdT3bW8z5EJMphYNIIh37IwSfLZY9800EWnrePvoj2rcX9ekXPfgsaztJrkLPe+EdSCcI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710338525; c=relaxed/simple; bh=CibDGutsPMp61sAS2V4hHhzK1ETvK8H23ZCWUNChrSk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=k8540YPq+21zJ0aWHGiZAoN8N1Ji/aPyN7yYTQqC4WGmPV88mRWDdkDwqGQJlgxkhjQxIHzMnqBF4t099DoDzCcmRvI0JYdx2pMhOuu035tKBrbBxIaOHptdmrxKhFHnGnSrJzYMJrrP5FcoThpyDJv18zPQ5seHsOYxAnYwZxM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=e0mUlR2j; 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="e0mUlR2j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6F241C43390; Wed, 13 Mar 2024 14:02:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1710338525; bh=CibDGutsPMp61sAS2V4hHhzK1ETvK8H23ZCWUNChrSk=; h=From:To:Cc:Subject:Date:Reply-to:From; b=e0mUlR2j72/2jkA1SxuGTBMek/bb25xSjBPIL/eHbVVwGlfg6URyKwH1q2Gc0LRfn GDTm/uKtk4dCiyiGHH/YlchUckRDCnAsc2gXgG6e4byvLDs3Rh0bsjtqWR2/PQH45r 0XpSIAJdLHXRqgyqY4xrmWIA9AkIphSg9fiRmUyrFba70/zJSuhHFadYTnOTZtCtPE CutFFCDgMxEIk5JDd/snOW72XcaILwkbWAF2O9GcKn4Fs3z6CBdegSwuyWEHOrIStF ET8NPe4I2hEha0v/XplLrrmH19YpCYWhEhd0KEgATOr1JvgyjWSbbIZe0jrr9H5wA4 aXNJgVHx+7SeA== From: Lee Jones To: linux-cve-announce@vger.kernel.org Cc: Lee Jones Subject: CVE-2024-26629: nfsd: fix RELEASE_LOCKOWNER Date: Wed, 13 Mar 2024 14:01:57 +0000 Message-ID: <20240313140155.1913910-4-lee@kernel.org> X-Mailer: git-send-email 2.44.0.278.ge034bb2e1d-goog Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Reply-to: , X-Developer-Signature: v=1; a=openpgp-sha256; l=5105; i=lee@kernel.org; h=from:subject; bh=CibDGutsPMp61sAS2V4hHhzK1ETvK8H23ZCWUNChrSk=; b=owEBbQKS/ZANAwAKAVGvii+H/HdhAcsmYgBl8bHTMPfX4t24gcc0aMaVKgyPvOygWuaXyPrde vzv/D2+OM+JAjMEAAEKAB0WIQR2tsk1o74gmpTwh0hRr4ovh/x3YQUCZfGx0wAKCRBRr4ovh/x3 YVsqEACpEMAGr5KOSQFOVQqCbWR5/O7ye9UtUmDplOHWNj6l9IG3gqXkqUNgV/bKUCHmqUs92Wa 3JSKXIGI/FBrPhftoFjDFcmSBiljvyRLyjfBmGv8RPE07cXc9Nb7Q00haRen9D1W21gdtXCETTC WQ3+OboNtgpam5ZxOouOkveSA6t3icdnOuq9K193Jrt3O5veuXP8MbqsAtR870Avb29BEwc1BX2 eNoiHk1aUUzaCWRTkk9Df9PBg5OtikZyrSUzg8765THTd94pcPAj7wV1d8XNXkyQotEhktugwFG njDDT1oiiWCQnYg+zZ0mcF7txa9SlOFbPVmzf2n/PqILt+6v2dengLMCWjoysTrx1+bTf/NXsQ+ QgzllnkxJWUdfzXtN9dhVZOZEKfpGBVVl3asJwZV1EFatq79sNd/zBFbDORbDeRp20NE2yjB6iY Pek8dUtonVOntO9hzMH5K3P5J4qpPaEZ7m8003UqahkyF0edpPJHV57mh15k+MewUft7AEaJfA8 mZa96wMZrCytcEVIHB/fy51roqceJE0ueoeNHesEQH0llVC9Ehm58NB4L/cqBH/JmOyGPdfD2gl w5Fklhy+wjxGpMaKKv/njut43+HdSaUxjUDJdlEDQIlIXsUB+nQQ00dGRmWTAYOu9493Zrvav8g cl0hWn2nCH58uDQ== X-Developer-Key: i=lee@kernel.org; a=openpgp; fpr=76B6C935A3BE209A94F0874851AF8A2F87FC7761 Content-Transfer-Encoding: 8bit Description =========== In the Linux kernel, the following vulnerability has been resolved: nfsd: fix RELEASE_LOCKOWNER The test on so_count in nfsd4_release_lockowner() is nonsense and harmful. Revert to using check_for_locks(), changing that to not sleep. First: harmful. As is documented in the kdoc comment for nfsd4_release_lockowner(), the test on so_count can transiently return a false positive resulting in a return of NFS4ERR_LOCKS_HELD when in fact no locks are held. This is clearly a protocol violation and with the Linux NFS client it can cause incorrect behaviour. If RELEASE_LOCKOWNER is sent while some other thread is still processing a LOCK request which failed because, at the time that request was received, the given owner held a conflicting lock, then the nfsd thread processing that LOCK request can hold a reference (conflock) to the lock owner that causes nfsd4_release_lockowner() to return an incorrect error. The Linux NFS client ignores that NFS4ERR_LOCKS_HELD error because it never sends NFS4_RELEASE_LOCKOWNER without first releasing any locks, so it knows that the error is impossible. It assumes the lock owner was in fact released so it feels free to use the same lock owner identifier in some later locking request. When it does reuse a lock owner identifier for which a previous RELEASE failed, it will naturally use a lock_seqid of zero. However the server, which didn't release the lock owner, will expect a larger lock_seqid and so will respond with NFS4ERR_BAD_SEQID. So clearly it is harmful to allow a false positive, which testing so_count allows. The test is nonsense because ... well... it doesn't mean anything. so_count is the sum of three different counts. 1/ the set of states listed on so_stateids 2/ the set of active vfs locks owned by any of those states 3/ various transient counts such as for conflicting locks. When it is tested against '2' it is clear that one of these is the transient reference obtained by find_lockowner_str_locked(). It is not clear what the other one is expected to be. In practice, the count is often 2 because there is precisely one state on so_stateids. If there were more, this would fail. In my testing I see two circumstances when RELEASE_LOCKOWNER is called. In one case, CLOSE is called before RELEASE_LOCKOWNER. That results in all the lock states being removed, and so the lockowner being discarded (it is removed when there are no more references which usually happens when the lock state is discarded). When nfsd4_release_lockowner() finds that the lock owner doesn't exist, it returns success. The other case shows an so_count of '2' and precisely one state listed in so_stateid. It appears that the Linux client uses a separate lock owner for each file resulting in one lock state per lock owner, so this test on '2' is safe. For another client it might not be safe. So this patch changes check_for_locks() to use the (newish) find_any_file_locked() so that it doesn't take a reference on the nfs4_file and so never calls nfsd_file_put(), and so never sleeps. With this check is it safe to restore the use of check_for_locks() rather than testing so_count against the mysterious '2'. The Linux kernel CVE team has assigned CVE-2024-26629 to this issue. Affected and fixed versions =========================== Issue introduced in 5.19 with commit ce3c4ad7f4ce and fixed in 6.1.79 with commit e4cf8941664c Issue introduced in 5.19 with commit ce3c4ad7f4ce and fixed in 6.6.15 with commit b7d2eee1f538 Issue introduced in 5.19 with commit ce3c4ad7f4ce and fixed in 6.7.3 with commit 8f5b860de870 Issue introduced in 5.19 with commit ce3c4ad7f4ce and fixed in 6.8-rc2 with commit edcf9725150e Please see https://www.kernel.org or a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2024-26629 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/nfsd/nfs4state.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/e4cf8941664cae2f89f0189c29fe2ce8c6be0d03 https://git.kernel.org/stable/c/b7d2eee1f53899b53f069bba3a59a419fc3d331b https://git.kernel.org/stable/c/8f5b860de87039b007e84a28a5eefc888154e098 https://git.kernel.org/stable/c/edcf9725150e42beeca42d085149f4c88fa97afd