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 A54444A440D for ; Thu, 24 Sep 2026 15:55:29 +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=1790265331; cv=none; b=gRDYnmaQuvKO4TbvjHXAWk2PLf9yvzO7qU55VP3JEkRYn/xDmnzt7q0dN3vGKWea23zylRpT3A1LiX7Tqnwo3Fr3yd0vUPW/GeOtJug6hVrCAcJ3YEBDgCJHcutUujBel922Ns26BoO797G8LL2VuyT5kPTQnNlRx/wNb/tTl90= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790265331; c=relaxed/simple; bh=VKZfMQe13sy5D2B3ps/qLysqsdwh/SsvSnpwEm2oLrQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=AJC1G1AgZCWdsinWLZUMcCV6WvjnRuRoeF5pl+Y8FB5OGnRnix4mmurCL4nYJNFAA/LTg6KnFpXeYlUNymhxw9Gp0H4pkiVVv2wZt9lFOrJwpfSmo02O8YGo2gf53+4l/v1nzRuM+/D6Aua2nJHLOT3S6nUmVuS7SBL6VRqZvCY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NPrZXBan; 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="NPrZXBan" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9F1C1F00893; Thu, 24 Sep 2026 15:55:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790265329; bh=RMCWiZwfKcAR6a9z/KxeqL7g/Emhw91NPblOTvSGNFk=; h=From:To:Cc:Subject:Date:Reply-To; b=NPrZXBanKsvc0IDhjLU5Q3gKEU7a+zxTJQmekioK4Kxa9lYzx0LLg82Qe2TmU81Ll iYFfAnyd3/Ozl/Jmla403XufwofgA69XWTT9sIKFW2Nr1vXxcd9m5C01VYZuCIuacZ 1sOZPAaLqCdX2MoG3jxxOcWYywGZpK+JtzNZdtjU= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-93275: perf/x86/intel/pt: Fix stop/start with no update Date: Thu, 24 Sep 2026 17:51:35 +0200 Message-ID: <2026092412-CVE-2026-93275-76ec@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=4098; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=GQFA4u5L2PVjBAIw1a67ahrIFQnmWaGN1k1bEcWdZeM=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlb3T5MfHtXYV17el2aczLrFBfBFo1HB65alc9ed02Oz 3G1tNC7jlgWBkEmBlkxRZYv23iO7q84pOhlaHsaZg4rE8gQBi5OAZiIwUOGBccfbXGJzjgqw/qC 3eNs1b4VxyoWTmVY0OVz6Ke2YvjvkPSbfOum2N5oWWXzGwA= 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: perf/x86/intel/pt: Fix stop/start with no update If pt_event_stop() is called without PERF_EF_UPDATE flag, then perf_aux_output_end() is not called. A subsequent call to pt_event_start() will call perf_aux_output_begin() again which violates the rule against nesting and triggers a WARNING in perf_aux_output_begin(). Originally, pt_event_stop() was never called without PERF_EF_UPDATE, because the only code paths to do so are from event overflow, and Intel PT does not do that. However the introduction of group throttling by commit 9734e25fbf5ae ("perf: Fix the throttle logic for a group") meant that an Intel PT event could be throttled if it was part of a group. Throttling calls PMU ->stop() / ->start() callbacks without flags. An example is when AUX area sampling is used. The following commands hit the issue: echo 10000 > /proc/sys/kernel/perf_event_max_sample_rate perf record -F32000 --aux-sample -e '{intel_pt//u,cycles:u}' \ -- bash -c 'for i in `seq 1 100000` ; do true ; done' Use PERF_HES_UPTODATE to track whether perf_aux_output_begin() and perf_aux_output_end() are balanced. A cleared PERF_HES_UPTODATE bit indicates that an AUX output context is still open. Amend pt_event_start() / pt_event_stop() accordingly so that begin/end stay balanced: - In non-snapshot mode, stop() always closes the buffer (the buffer may have run out of space, and that accounting is done by the update), so a following start() opens a fresh one as before. - In snapshot/overwrite mode, stop() without PERF_EF_UPDATE leaves the buffer open so that pt_event_snapshot_aux() can still copy from it, and start() then only re-enables tracing instead of calling perf_aux_output_begin() again. Note that pt_event_del() calls pt_event_stop() with PERF_EF_UPDATE flag set (as is required by the documentation), so a final call to perf_aux_output_end() is assured. The Linux kernel CVE team has assigned CVE-2026-93275 to this issue. Affected and fixed versions =========================== Issue introduced in 4.1 with commit 52ca9ced3f70779589e6ecc329baffe69d8f5f7a and fixed in 6.12.110 with commit 9b919fb5512f256e9e0604faf960b2bb98aab454 Issue introduced in 4.1 with commit 52ca9ced3f70779589e6ecc329baffe69d8f5f7a and fixed in 6.18.52 with commit cab5015ee3f25f789b4a368f2abfa65536576b78 Issue introduced in 4.1 with commit 52ca9ced3f70779589e6ecc329baffe69d8f5f7a and fixed in 7.2.6 with commit 304844b5545f444d523286da8228a1cbc46ffffa Issue introduced in 4.1 with commit 52ca9ced3f70779589e6ecc329baffe69d8f5f7a and fixed in 7.3-rc1 with commit 2e17bf3a469a41457a3bc31b1f8fd66b6ce94a6d 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-2026-93275 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: arch/x86/events/intel/pt.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/9b919fb5512f256e9e0604faf960b2bb98aab454 https://git.kernel.org/stable/c/cab5015ee3f25f789b4a368f2abfa65536576b78 https://git.kernel.org/stable/c/304844b5545f444d523286da8228a1cbc46ffffa https://git.kernel.org/stable/c/2e17bf3a469a41457a3bc31b1f8fd66b6ce94a6d