From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f43.google.com (mail-pj1-f43.google.com [209.85.216.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E80213B4417 for ; Mon, 17 Aug 2026 14:07:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.43 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786975637; cv=none; b=kaYGtS7bE9vY6RxLyI0JI8Fht9vyu+a5QJ8vfrhmuLwUUY2PJnVaIe8fz5LvP40eGwwZUydv0wDU2YuME3/p44cdqOcCJzuUvMn9JoI4AWxforMO4KobgddL6RAe9nFCK784fJRQwoBJdtlJKYGEAahCKlV2GEbCM/2FPWi7Tz0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786975637; c=relaxed/simple; bh=IfA4RcyEEepafQjD6vZ+iwdtqEflKw8Y5zNbQ3WkdlM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Yw01OfSfJBPSe/Y9UlV2+PZlm92UfdHYvyuUqb+K607TC8wviGh7XTTSOyX4fX7KjzxcCEnwGyS2L+BBbiEGv+EgKSAGstBtJv+Ap8sqS0BnK2kmGo0iy5K7iDLFKHl2yr9bOSutM5szQv9fUKajGkqg8aJt89kJXqCI/MP2I5c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=O94DbQrB; arc=none smtp.client-ip=209.85.216.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="O94DbQrB" Received: by mail-pj1-f43.google.com with SMTP id 98e67ed59e1d1-382ef647e20so3256561a91.1 for ; Mon, 17 Aug 2026 07:07:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1786975635; x=1787580435; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=7R7rzLw9gb3ERMXW4LdXL81RMv+1OVwFG3xXvh/QwrY=; b=O94DbQrBEia3NWhMB5HtXmuPDSmir/Eq/Vud9JNJtRabrqDJ4ARn+oMrHTbY23cOhi wIn1xRLPg6MokMq5TT52hIA8fVXELQ0boC2a0xKeGlJ2Lhjqk9RJi5N6/YXebr9Jg9tJ IdCUG7swe47F0NS2hbIT0K76OMbJFRZo6EulY8+DJeZNGE84XfZSCs7hj7z3axSMCr+9 8kektY22TpRscKTpTcOz5cj6bmHP1rtu8qFvOqh7SU/bOhk0PGCkedUv7y6/W7k/8XfK L8MVCp7bO4zQ5xrvhR27cy0GQ4+R6a/OcMySAJ1wb/jJYMZvBtfyavNf/TSwUTF7GUr8 71eQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786975635; x=1787580435; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=7R7rzLw9gb3ERMXW4LdXL81RMv+1OVwFG3xXvh/QwrY=; b=GXb7fMAyRkSWU/6TOG2WwZnpESH+MDP+6Ab84HJgSccwGLDaPu1P2sHXOGkUbyEjLJ WgKSpS2opcL5HDqizfoJLBMdE0EQnXYx/35NRTdCI0blorxIUDgNrXKtRpnvfLCldKy0 M8dHWbM+MqpztUtdm6l3PyrlDbIUnA3Ply+i7P2qtbePAWEYSAyvyopcWFwHj2eZz3BH DfyCQxFEMWihVoJ9LQECn1EXpi3S0yvvTjEq4HQJ8G/k8NAhycf0y5S1pFaYxT3ydh3/ fcrGdBM6gb6Xswz/2yry/LYxNVUN5UAUlq6EQgCGod9jsA8snns6AxXmRET57ufM5DKp gIFw== X-Forwarded-Encrypted: i=1; AHgh+Rp4qayieHk6IYIQsTXB1heTdY5qBwr/r63d9YdoaMPFwK3jP1F9h4d1joEc//2dEfi4mvjaXLuHFu3pTZhh0zkFSsI=@vger.kernel.org X-Gm-Message-State: AOJu0YwW2cXQtpjDrK1KhlG8ZbALfEurXw5nN5zbY9pF2xwlLoj8bSWm LV5cNsiUhcI0kbv0DxiWXv3aYVsAXbQdVrs39O4hiZHyPfS1OrkeGF12 X-Gm-Gg: AR+sD10V0Wo0jqwMoUFu25Dg07+0j5BFnlDe/xbQ26IkMUMQScPOtBEH5SE9V9Lbxt3 veOhY851XQR36eriaw78qqyjH8HNtcXYrWPBeqkDkoBKCPlRrx5Kp6dWy/KxpDoDnqquZyhxXuU 1ciIjYGXFmhqe4aYh3/4uwEfdqIjNo7tmatulf0f8NfECI6yhZc1SnkfXf6/ANdm5c9zT0aWDUb aFv7ASjGWZuNb48ZuPuTL36bxVbs0F3S3yEfMuMD6PUV6oqFEz3swoCr9xQYFeetC1tOpTwc7xm jlI0q2L56R+C2oRm0W1sl19KPVDVHMLfwZ0MZ9keWSuaMFL0TpKDFKJlDLQ9Z7KlCF25JNMKQsE DBN/LtzJV+fJpSSLQJ2omKXifW1OMIDk4P6hjunLvnuwyFCx6qOea/I9rXyIIfDW8kHMhPkJBtb UfvkGvM5j51SyT5z/3AEtO54bqSD48SY3F9lGX37X4TjG4ZT8NsaZjCF2i1+L7zR3yJVc3et3up U2+NK2RqIvEwlPPGjVf5hyMUGRZw2LEmLwcvrg0xz86ozHZfDo= X-Received: by 2002:a17:90b:4f:b0:38e:ad9d:1161 with SMTP id 98e67ed59e1d1-3933b833613mr29953901a91.0.1786975635227; Mon, 17 Aug 2026 07:07:15 -0700 (PDT) Received: from deepanshu-Legion-Pro-5-16AFR10.. ([2405:201:682f:383f:f2f:4085:2896:a1e]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3954d2b6efcsm2415655a91.1.2026.08.17.07.07.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 07:07:14 -0700 (PDT) From: Deepanshu Kartikey To: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com Cc: tz.stoyanov@gmail.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+685955db58555575fdd2@syzkaller.appspotmail.com Subject: [PATCH] tracing: Fix use-after-free in trace_pipe read on sub-buffer order change Date: Mon, 17 Aug 2026 19:36:55 +0530 Message-ID: <20260817140655.5694-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page, and replaces them with newly allocated ones. Readers of trace_pipe hold pointers into those pages. ring_buffer_peek() looks up an event under cpu_buffer->reader_lock but returns the event pointer after dropping the lock, and peek_next_entry() then calls ring_buffer_event_length() and ring_buffer_event_data() on it. If the sub-buffer order is changed in that window, the reader dereferences freed memory: BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430 Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002 Freed by: free_buffer_page kernel/trace/ring_buffer.c:398 [inline] ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444 buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221 Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change. This is the lock trace_pipe readers already hold across their entire peek-and-print loop, so the swap can no longer race with a reader that is dereferencing a peeked event. Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page") Reported-by: syzbot+685955db58555575fdd2@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=685955db58555575fdd2 Tested-by: syzbot+685955db58555575fdd2@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey --- kernel/trace/trace.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 395238b2b715..c38a5de602e0 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8214,6 +8214,8 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf, /* Do not allow tracing while changing the order of the ring buffer */ tracing_stop_tr(tr); + trace_access_lock(RING_BUFFER_ALL_CPUS); + old_order = ring_buffer_subbuf_order_get(tr->array_buffer.buffer); if (old_order == order) goto out; @@ -8253,6 +8255,7 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf, #endif (*ppos)++; out: + trace_access_unlock(RING_BUFFER_ALL_CPUS); if (ret) cnt = ret; tracing_start_tr(tr); -- 2.43.0