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 1A9AA3EF67D for ; Fri, 8 May 2026 14:25:03 +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=1778250303; cv=none; b=qTCK8LFIsPeztCFia8Mb8WFARNXaRwMx1mLMbxhyI2BFW7VgwDHOxabW8d5Tp4R0j9NiUpugMRF2gKyisUF5bGFg/yrhlyG+WLX9RxQCoIGczdeIEe1GX15/elL4PQv+pWvqbcB5EPnPLxRkjeleNMVwHiqiKtn0oCvC2Q4WX/A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778250303; c=relaxed/simple; bh=0/kcTe0W7JLckPdZbdr22TiV/JRcvNIz/mUOY5A826w=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=s+0IMgupRK+UsoshULP4p3nUfn+/t9L4K/gt6RqIqSOKyeU1Gi42odRoa5G/E+t0eEIvqbCl1+TvERFVwrf2RKJghq+4FYhkvUuYfcPk7vwf0T9pkLmfGOV6BWDsQSWRBlonVvQRqxbt+J58t0IsFlUG7EXPTbFp45OqZU56MG4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rvqYnvJu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="rvqYnvJu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AAC40C2BCB0; Fri, 8 May 2026 14:25:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778250303; bh=0/kcTe0W7JLckPdZbdr22TiV/JRcvNIz/mUOY5A826w=; h=From:To:Cc:Subject:Date:Reply-To:From; b=rvqYnvJu+3yuz2duqkJkGmEZqD9TaZ3P0kuvzveIeC9FV/vl3x9cPG96v9rivDTeh ul7oV34i6enLY8ewtWc+8pozB0NIqBGpUmZz6uYmU5m1eFwCh1xN2y3AZCu1KuNYup 8kNsAOJOUlErS1TFJnJGOvzELFPSK8/rQFWJmtw4= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-43392: sched_ext: Fix starvation of scx_enable() under fair-class saturation Date: Fri, 8 May 2026 16:22:01 +0200 Message-ID: <2026050837-CVE-2026-43392-00ee@gregkh> X-Mailer: git-send-email 2.54.0 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=3340; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=3HQBmfppb1Jz/CWSrmLOG1LIL2MpeZmBVdD1xbAMuz4=; b=owGbwMvMwCRo6H6F97bub03G02pJDJl/Pxbu3VrpqTxJOuflkXbm4A9bOzpN7Uq3Ht+rECvA5 FYbcmlfRywLgyATg6yYIsuXbTxH91ccUvQytD0NM4eVCWQIAxenAExk212GeUqsS+ana3s6dAlv OnXipvSz+Sv9xRkWdDE+bPZWf3dGa+I8lfKJYlm/1F/UAAA= 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: sched_ext: Fix starvation of scx_enable() under fair-class saturation During scx_enable(), the READY -> ENABLED task switching loop changes the calling thread's sched_class from fair to ext. Since fair has higher priority than ext, saturating fair-class workloads can indefinitely starve the enable thread, hanging the system. This was introduced when the enable path switched from preempt_disable() to scx_bypass() which doesn't protect against fair-class starvation. Note that the original preempt_disable() protection wasn't complete either - in partial switch modes, the calling thread could still be starved after preempt_enable() as it may have been switched to ext class. Fix it by offloading the enable body to a dedicated system-wide RT (SCHED_FIFO) kthread which cannot be starved by either fair or ext class tasks. scx_enable() lazily creates the kthread on first use and passes the ops pointer through a struct scx_enable_cmd containing the kthread_work, then synchronously waits for completion. The workfn runs on a different kthread from sch->helper (which runs disable_work), so it can safely flush disable_work on the error path without deadlock. The Linux kernel CVE team has assigned CVE-2026-43392 to this issue. Affected and fixed versions =========================== Issue introduced in 6.12 with commit 8c2090c504e998c8f34ec870bae71dafcc96a6e0 and fixed in 6.12.78 with commit e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b Issue introduced in 6.12 with commit 8c2090c504e998c8f34ec870bae71dafcc96a6e0 and fixed in 6.18.20 with commit c44198f25fdfecc0ec0fe366bf8a47fe17d8e229 Issue introduced in 6.12 with commit 8c2090c504e998c8f34ec870bae71dafcc96a6e0 and fixed in 6.19.9 with commit 05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81 Issue introduced in 6.12 with commit 8c2090c504e998c8f34ec870bae71dafcc96a6e0 and fixed in 7.0 with commit b06ccbabe2506fd70b9167a644978b049150224a 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-2026-43392 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: kernel/sched/ext.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/e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b https://git.kernel.org/stable/c/c44198f25fdfecc0ec0fe366bf8a47fe17d8e229 https://git.kernel.org/stable/c/05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81 https://git.kernel.org/stable/c/b06ccbabe2506fd70b9167a644978b049150224a