From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 CF55133F8CA for ; Sat, 22 Aug 2026 15:33:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787412833; cv=none; b=o60WqGxlCmr5eonHnKxcBIEQWCN/oX7h9QLYvohhRA2SrxeNGzp2TeMK6qvZ+x2PG0zXqQxXG1m3gIBDr3jlhH+EJAv3+dlwc8fNWtkSKhQnxK44mFGIHuQqwwM40rJH4rjwMLI9HcWbcm1cPqbId0pmvLaU1zFCqkJsIPukyj0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787412833; c=relaxed/simple; bh=8+Kg6sYLmaYBPmef2dMGAdydY87ph069gKnfNtAuXwc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=HKH6+lKSz4atwWk/uJOODowRFEMB79I1YgbDFk5nXonySCpqxbKeNQUZta0bR4cujatE4drWaEFkOONMWJUgenozNg3bICGHrJELI2pKMlC81Jge6dwh3UfMpuFBaUrgOz1N28Qc0yuaiBpG81EPbVEaztjH+lqO2GCMGDVG0uE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f2o9kKyM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="f2o9kKyM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A26351F000E9; Sat, 22 Aug 2026 15:33:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787412831; bh=6J3JJ8+1tIq5rfXkyKOcFTDlOxWA0WE0bJh5LvBnwqM=; h=From:To:Cc:Subject:Date:Reply-To; b=f2o9kKyM7p0xfXEYRq4CI2f4pTq98FADvM0f2DIoDuaxL+APL5l4pMz4BPGXuBEEw S/oGu54GDhpAuAfhSXvWntF1kH7AKzZFRglSoDpUO7vp9YHvwbw+Yyq7sHT3FdAUqq 6JvYifK07WYc17ntkYGPcZ7eD9SM8nZsPGVy0jcU= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-74599: mm/ptdump: always stabilise against page table freeing using init_mm Date: Sat, 22 Aug 2026 17:31:23 +0200 Message-ID: <2026082215-CVE-2026-74599-b213@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3607; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=dBfEdBstwyadXrTncCYra1BNR5ZeMbvTcA9SDh0VfI8=; b=owGbwMvMwCRo6H6F97bub03G02pJDFmdBw5/PyA/bb3/jqXL7jXn79y8wO36atv90oZWnPW8k XL3Xu182hHLwiDIxCArpsjyZRvP0f0VhxS9DG1Pw8xhZQIZwsDFKQAT6ZrBsGAH37nFS0LVP3o2 2T1/reEX9u5BQyTD/Bj2716NtdVWDDyLNd4+epJ0biffDwA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: mm/ptdump: always stabilise against page table freeing using init_mm Previous commits have established the invariant that kernel page table freeing is performed while an mmap read lock on init_mm is held, which fixes races between ptdump and kernel page table freeing over init_mm. However, x86 and arm64 can perform a ptdump over an mm other than init_mm via ptdump_walk_pgd() and since kernel memory ranges are shared across non-kernel mm's, this means that the race still exists for these cases. Fix this by acquiring a nested mmap write lock for init_mm in ptdump_walk_pgd(). This is safe as we take this after mmap write locking the mm, and nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code, and eliminate the unnecessary and confusing invocation of walk_kernel_page_table_range(). We can safely remove the non-NULL check for walk.mm, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The first point at which ptdump can race kernel page table freeing is commit b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table"), so we target this in the Fixes tag. The Linux kernel CVE team has assigned CVE-2026-74599 to this issue. Affected and fixed versions =========================== Issue introduced in 4.16 with commit b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e and fixed in 6.18.45 with commit 7f740664aec1f832953c2e6d9b8920cd6c8bcc0c Issue introduced in 4.16 with commit b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e and fixed in 7.1.9 with commit 4adc4c9a9a43d61fe476dfe10811f3df2e7e4106 Issue introduced in 4.16 with commit b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e and fixed in 7.2 with commit 27c32e5538344b13c1505a08861e04620c125d47 Issue introduced in 4.4.125 with commit 31895cfd79564111cdd5a9f48c5d491ae26a238e Issue introduced in 4.9.91 with commit 9c7f7bdb1932f8c1e5f80d32c717184701afe701 Issue introduced in 4.14.31 with commit acdb4981644c8e31ccee294bdefff475c0cf587b Issue introduced in 4.15.14 with commit 0454e2fad9306961540ee7e84da47a8e345b7d22 Please see https://www.kernel.org for 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-2026-74599 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: mm/pagewalk.c mm/ptdump.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/7f740664aec1f832953c2e6d9b8920cd6c8bcc0c https://git.kernel.org/stable/c/4adc4c9a9a43d61fe476dfe10811f3df2e7e4106 https://git.kernel.org/stable/c/27c32e5538344b13c1505a08861e04620c125d47