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 7ED9441F35E; Sat, 12 Sep 2026 13:27:55 +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=1789219676; cv=none; b=sufXYDQiAjzskhkIQE8A1+ysT+FOpuubx+chRoG7r7NrCiqkHFIJq6SVXaw2r/gA2uvLzN5jJh/6GEUKxF5PGLl1NOi0Kejxf7P9tA1FGGUIWAxYji7qLhDtaXToodYMTblx8SHGaV0eAT12rIOUBFBAzpyQy/OuiYoc3DH1sB8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789219676; c=relaxed/simple; bh=izWLmrAQKYWx5bKKu1SNM1XNTbz/Pyc9DquOvNbQDyg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UV3oWFq5a8q19AfOGGiFamwQJlkRnPhGP8vioMbxo+M/UD3+EXmCDVOamIm79y0vL4EsmMtYrWwcS2vpb1aEkm77SeSIAaT6GQ3Ooxy6EaYmUzhE5rzG+nRkG7920gIlazGxOixW9OR3suIlDZcuETdrIYjuMuSt2oAKdSHSlfw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EXuwlcUa; 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="EXuwlcUa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC4BB1F000FF; Sat, 12 Sep 2026 13:27:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789219675; bh=2S+//Fcolfk2Ye2bT3W0xLRKGAcUGaPfkIvO+4nQUN4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EXuwlcUaLFPJgapuebwrv2Dyrm0yNG85UMvnEirv1zgJyMCEEXZG2bSCF5Q9g/4zQ ECsguh45RFK4/ITpCsB5LBA3mYdL7WfsokegIVmrDXMMe3qftEnpChwMMHEmj1iqUj 9RVSHcT4F3yP5gKJlWrJDzHRPfEIviQ1qZAUu5Uk= 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 6.6 0022/1424] tracing/user_events: Clear copied tracing state before fork duplication Date: Sat, 12 Sep 2026 08:40:54 +0200 Message-ID: <20260912065607.801305267@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065607.279695368@linuxfoundation.org> References: <20260912065607.279695368@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 6.6-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 @@ -850,6 +850,9 @@ 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;