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 BD57D5867E8 for ; Fri, 11 Sep 2026 20:06:49 +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=1789157214; cv=none; b=Ewt0N4/tzuZbmD4VOhNWoT2UvwcvNmZoqkYcpEOOzmEyOKYJjoJUz2W2/pxO/8Nz2B+xm5iim28VACfFGWnzvmksrqag/MPtb/WUInVdjaEIH0zQeFcOnNnTpDrmEh9/ahDC11gpFHB8EBcg+v9Hv6bliVxpEbRb0rgPFJxeD3E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789157214; c=relaxed/simple; bh=6Vq7euF6fBos0PAYRcAlzZVEltR6t/+SyLGKcIOMrVs=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=NTrnjFRFR34qUH4SgGafq+Cb3nopcJyG2ilsXoqItICU7F10QvNFqeqxfocoTPMD9thEdCUkz1RBL5tDuQwEt4M9J+6VTghnbKE81SC1W7I3ZEGSzU0b7JDxIyebcG7qYILRC3dxSFep0sa6lSeKyMRDeI6h5GNl3NuMSDPW42M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=x5f4mmeK; 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="x5f4mmeK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84D801F000FF; Fri, 11 Sep 2026 20:06:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789157208; bh=5NqPfJxzYDJ72AwtgTgSahfoJSKK/FJgEfdoge2G044=; h=From:To:Cc:Subject:Date:Reply-To; b=x5f4mmeKb61rinftOnVQo4PmgamMDl2YDLQpJVT2dIJxp5zwll8DDb928FqKPvkcB 9NqmjLTc4ssp5DJMjkD8+gRqeVqmC7hZDmEWxJjNDjSC29lXZqh1EYAFADsMizhGWv 75j07zqoPMkc8RXY4KMKlX3f5hVa0QGVbNf4kF8k= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89771: ring-buffer: Fix subbuf resize race with ring buffer readers Date: Fri, 11 Sep 2026 21:47:40 +0200 Message-ID: <2026091111-CVE-2026-89771-a8d9@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=2993; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=5iL+TEWhZmIOtNq1K/RRgbKS/cf75jq9F8FDpSsL3kk=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIidbV8ZFfN5p/NBLtmTaq4T/dWrv7PYc9DhYzSB1Q YDp2Pm4jlgWBkEmBlkxRZYv23iO7q84pOhlaHsaZg4rE8gQBi5OAZjI8iqGuTI97BM9Rf7+na67 66fn6k6+yAwxNYY5nOys/Z8ubClnFV/xNDv656Qla9+LAAA= 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: ring-buffer: Fix subbuf resize race with ring buffer readers trace_buffer subbuf_size is read lockless in ring_buffer_read_page() and ring_buffer_read_start(), while it can simultaneously be resized with ring_buffer_subbuf_order_set(). Instead of trace_buffer::subbuf_size, use bpage::order in ring_buffer_read_start() and ring_buffer_read_page(). In ring_buffer_read_start(), even with resize_disabled, there is still a possibility of a race with a buffer modification. Hold the trace_buffer mutex to synchronise with any pending ring buffer order modification. trace_buffer::subbuf_size is now actually useless, remove it. Also, create accessors rb_subbuf_capacity() and rb_page_capacity() which return the actual size available for storing events, while rb_subbuf_size() returns the actual subbuf page-size. The Linux kernel CVE team has assigned CVE-2026-89771 to this issue. Affected and fixed versions =========================== Issue introduced in 6.8 with commit f9b94daa542a8d2532f0930f01cd9aec2d19621b and fixed in 6.12.109 with commit 6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9 Issue introduced in 6.8 with commit f9b94daa542a8d2532f0930f01cd9aec2d19621b and fixed in 6.18.50 with commit 50f4a793c4ff24826efb0ac700989a5063cc53df Issue introduced in 6.8 with commit f9b94daa542a8d2532f0930f01cd9aec2d19621b and fixed in 7.2.4 with commit 0c7c517827a453128a8f58bfd849546a29813b27 Issue introduced in 6.8 with commit f9b94daa542a8d2532f0930f01cd9aec2d19621b and fixed in 7.3-rc1 with commit 8a5f63637890f03177146efddaba5ec7a1b4d61f 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-2026-89771 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/trace/ring_buffer.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/6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9 https://git.kernel.org/stable/c/50f4a793c4ff24826efb0ac700989a5063cc53df https://git.kernel.org/stable/c/0c7c517827a453128a8f58bfd849546a29813b27 https://git.kernel.org/stable/c/8a5f63637890f03177146efddaba5ec7a1b4d61f