From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 613421581EE; Wed, 16 Jul 2025 23:30:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752708631; cv=none; b=tqMZ1VWAR4uUWb+ZamDMTFyCdmd3DZPTxFSxYkSff9LMArO3tPmmVdOmG4WGiHH0L0n/sxeVEQ00vypfmF/zVGO6zZMaeHdfrzNpeqStiH10Dc+FZcLxdhdLYYHfdplz1aN6je+iDWduieEFrX56QPLR3NJQLO2hU1NXa30uekM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752708631; c=relaxed/simple; bh=vpdb/FFt82flKJIlBIGoF5aG80XhB46NBHmh2lM03uc=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=n0LuBSKY51+zLTjuU20ZygYYn/o/QRAW95/AMT07IAQE2tDE02Lpxk7gRqAig1zrjiSmxojctFYgxPLrImsgo3gvcq9Z/G/zidIPbCV3rhheK8YGyC8Ls1czZz0k36kE8xgzyO54RZOLlwM3qVAlduWPJmL8ri+hlJLI0LeCb2Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nrjYBFfa; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nrjYBFfa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D36B7C4CEE7; Wed, 16 Jul 2025 23:30:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752708631; bh=vpdb/FFt82flKJIlBIGoF5aG80XhB46NBHmh2lM03uc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=nrjYBFfaal/qo7FKu/29xl0g9B/XGO7Gq34qJoAGs0EMXUva0GMOpTHaiwRA6fq76 tsnAuh0w+s4wbMuSKous34uLGzbRbz3w527XdjGQeGYLaHVXj32bp7v24Ha8Jp0JDC rBCzLLjK9VazlF2l6s+mSXNPKgt4yKWQQbAo50VjXJBQnnIovXwNAhniCjXrWLqome mtt5+kmRpOSJRrkczlLGac32nLYwoB7hERm/kyMi87YfIZ9gH+gBy++TKf6WUdyexy WkVYsQGKDLsh73crE27V/T0+H9JSCyiluZInNMhvxbDYk84VTdX5AqbjFsYfl5Xk39 gv1CSGaNzAHzg== Date: Thu, 17 Jul 2025 08:30:28 +0900 From: Masami Hiramatsu (Google) To: Tomas Glozar Cc: Steven Rostedt , Linux Trace Kernel , LKML , John Kacur , Luis Goncalves , Attila Fazekas Subject: Re: [PATCH] tracing/osnoise: Fix crash in timerlat_dump_stack() Message-Id: <20250717083028.823c06845d60927b6773322f@kernel.org> In-Reply-To: <20250716143601.7313-1-tglozar@redhat.com> References: <20250716143601.7313-1-tglozar@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 16 Jul 2025 16:36:01 +0200 Tomas Glozar wrote: > We have observed kernel panics when using timerlat with stack saving, > with the following dmesg output: > > memcpy: detected buffer overflow: 88 byte write of buffer size 0 > WARNING: CPU: 2 PID: 8153 at lib/string_helpers.c:1032 __fortify_report+0x55/0xa0 > CPU: 2 UID: 0 PID: 8153 Comm: timerlatu/2 Kdump: loaded Not tainted 6.15.3-200.fc42.x86_64 #1 PREEMPT(lazy) > Call Trace: > > ? trace_buffer_lock_reserve+0x2a/0x60 > __fortify_panic+0xd/0xf > __timerlat_dump_stack.cold+0xd/0xd > timerlat_dump_stack.part.0+0x47/0x80 > timerlat_fd_read+0x36d/0x390 > vfs_read+0xe2/0x390 > ? syscall_exit_to_user_mode+0x1d5/0x210 > ksys_read+0x73/0xe0 > do_syscall_64+0x7b/0x160 > ? exc_page_fault+0x7e/0x1a0 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > > __timerlat_dump_stack() constructs the ftrace stack entry like this: > > struct stack_entry *entry; > ... > memcpy(&entry->caller, fstack->calls, size); > entry->size = fstack->nr_entries; > > Since commit e7186af7fb26 ("tracing: Add back FORTIFY_SOURCE logic to > kernel_stack event structure"), struct stack_entry marks its caller > field with __counted_by(size). At the time of the memcpy, entry->size > contains garbage from the ringbuffer, which under some circumstances is > zero, triggering a kernel panic by buffer overflow. > > Populate the size field before the memcpy so that the out-of-bounds > check knows the correct size. This is analogous to > __ftrace_trace_stack(). > Looks good to me. Acked-by: Masami Hiramatsu (Google) Thank you! > Cc: stable@vger.kernel.org > Fixes: e7186af7fb26 ("tracing: Add back FORTIFY_SOURCE logic to kernel_stack event structure") > Signed-off-by: Tomas Glozar > --- > kernel/trace/trace_osnoise.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Note: This has been so far only reproduced on laptops (three different > machines). Not sure what the reason for that is, but it is clearly > a bug. > > diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c > index 6819b93309ce..fd259da0aa64 100644 > --- a/kernel/trace/trace_osnoise.c > +++ b/kernel/trace/trace_osnoise.c > @@ -637,8 +637,8 @@ __timerlat_dump_stack(struct trace_buffer *buffer, struct trace_stack *fstack, u > > entry = ring_buffer_event_data(event); > > - memcpy(&entry->caller, fstack->calls, size); > entry->size = fstack->nr_entries; > + memcpy(&entry->caller, fstack->calls, size); > > trace_buffer_unlock_commit_nostack(buffer, event); > } > -- > 2.47.1 > > -- Masami Hiramatsu (Google)