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 D62743AA187; Fri, 4 Sep 2026 05:40:44 +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=1788500446; cv=none; b=cBkadlJHkAvY0vpnyChLfLr7Rr8JQHu6twM11SPZQuHop0x7Tf5s6K5eCg5WFiDkJRNE3Coen3D48rYowaXWjrGdFVParQV5pY7zWL6qcIVH3wIujBUkPKLlLa8EtulJlgROaFUh9LPlmwE9sXkvm340EFlsxfbETGBryFdmTF4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788500446; c=relaxed/simple; bh=XhKvc3cGNbhu7i1gMXjYu+ebu4CcoyZup/wzBJF9EYI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mdYcZCiK69LMOjpG8qUBFuHjFqw5Uz417vSiPnQ4Ty+IDQzBEq7f+6LFuE7I1yLQTKP3WY2G7OboIEJt1q1L6qku0a1AKlTdrpgRo9cwOX3d72fOlzBnGQReYll9DxHb4vN71SOrfpR8pDJnKU/MQgIl/3IJs07fC4wTgkeB0Go= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IRgO81b3; 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="IRgO81b3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A5501F00A3D; Fri, 4 Sep 2026 05:40:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788500444; bh=35t7TY//agjn/jjFydkaD881NlAITI/lfVs2AE+5XM8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IRgO81b3KNvcYH6ZRbwsNQ5LRhC+05HHr2NLPpcVgzpfIfjUnLSbKqVq34nPtmWy5 RNENzvv7Y9dMJ+XsM4ElZt7SyMUX+WrBhZFuKvJpM9sgZjAU3tIEXz20xsY/MJnQYp wbkQqweKkL0o99W3HdMa9SjG/CCZzAzbVnwTAr6U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= , Bradley Morgan , Steven Rostedt Subject: [PATCH 6.18 058/552] tracing/user_events: Clear copied tracing state before fork duplication Date: Fri, 4 Sep 2026 06:53:35 +0200 Message-ID: <20260904045749.162475549@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jérémy Jean commit 390f6bd8583d177029d9df4bea6667509e55a765 upstream. dup_task_struct() copies user_event_mm from the parent into the child, without grabbing a reference to it. user_event_mm_dup() should replace it, but it leaves that copied pointer unmodified if user_event_mm_alloc() fails. When the child exits, user_event_mm_remove() decrements a reference the child never owned, which ultimately frees user_event_mm, while the parent still as a stale pointer to it. This creates a UAF, which KASAN reports as: BUG: KASAN: slab-use-after-free in current_user_event_mm+0x51/0x1d0 Write of size 4 at addr ffff888005010d30 by task init/44 Call Trace: kasan_report+0xce/0x100 kasan_check_range+0x10f/0x1e0 current_user_event_mm+0x51/0x1d0 user_events_ioctl+0x82e/0x15c0 __x64_sys_ioctl+0x139/0x1c0 do_syscall_64+0xce/0x450 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 44: __kasan_kmalloc+0x8f/0xa0 __kmalloc_cache_noprof+0x180/0x3a0 user_event_mm_alloc+0x3c/0x1f0 current_user_event_mm+0x88/0x1d0 Freed by task 42: __kasan_slab_free+0x43/0x70 kfree+0x13a/0x390 process_one_work+0x696/0xf90 worker_thread+0x420/0xba0 The fix simply clears the copied pointer before any possible failure. In case of failure, the child then has nothing to free. Cc: stable@vger.kernel.org Fixes: 7235759084a4 ("tracing/user_events: Use remote writes for event enablement") Link: https://patch.msgid.link/20260827184321.2964601-2-Jeremy.Jean@oss.cyber.gouv.fr Assisted-by: Codex:gpt-5 Signed-off-by: Jérémy Jean Reviewed-by: Bradley Morgan Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_user.c | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -868,6 +868,9 @@ void user_event_mm_dup(struct task_struc struct user_event_mm *mm = user_event_mm_alloc(t); struct user_event_enabler *enabler; + /* On failure, do not free parent's copy */ + t->user_event_mm = NULL; + if (!mm) return;