From: Breno Leitao <leitao@debian.org>
To: Markus Boehme <markus.boehme@mailbox.org>
Cc: stable@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
Simon Horman <horms@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6.12] netconsole: avoid OOB reads, msg is not nul-terminated
Date: Tue, 4 Aug 2026 01:04:57 -0700 [thread overview]
Message-ID: <anGdHcAGMUbblP2c@gmail.com> (raw)
In-Reply-To: <20260803184129.24594-2-markus.boehme@mailbox.org>
On Mon, Aug 03, 2026 at 08:41:29PM +0200, Markus Boehme wrote:
> From: Jakub Kicinski <kuba@kernel.org>
>
> [ Upstream commit 82aec772fca2223bc5774bd9af486fd95766e578 ]
>
> msg passed to netconsole from the console subsystem is not guaranteed
> to be nul-terminated. Before recent
> commit 7eab73b18630 ("netconsole: convert to NBCON console infrastructure")
> the message would be placed in printk_shared_pbufs, a static global
> buffer, so KASAN had harder time catching OOB accesses. Now we see:
>
> printk: console [netcon_ext0] enabled
> BUG: KASAN: slab-out-of-bounds in string+0x1f7/0x240
> Read of size 1 at addr ffff88813b6d4c00 by task pr/netcon_ext0/594
>
> CPU: 65 UID: 0 PID: 594 Comm: pr/netcon_ext0 Not tainted 6.19.0-11754-g4246fd6547c9
> Call Trace:
> kasan_report+0xe4/0x120
> string+0x1f7/0x240
> vsnprintf+0x655/0xba0
> scnprintf+0xba/0x120
> netconsole_write+0x3fe/0xa10
> nbcon_emit_next_record+0x46e/0x860
> nbcon_kthread_func+0x623/0x750
>
> Allocated by task 1:
> nbcon_alloc+0x1ea/0x450
> register_console+0x26b/0xe10
> init_netconsole+0xbb0/0xda0
>
> The buggy address belongs to the object at ffff88813b6d4000
> which belongs to the cache kmalloc-4k of size 4096
> The buggy address is located 0 bytes to the right of
> allocated 3072-byte region [ffff88813b6d4000, ffff88813b6d4c00)
>
> Fixes: c62c0a17f9b7 ("netconsole: Append kernel version to message")
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Reviewed-by: Simon Horman <horms@kernel.org>
> Link: https://patch.msgid.link/20260219195021.2099699-1-kuba@kernel.org
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Breno Leitao <leitao@debian.org>
prev parent reply other threads:[~2026-08-04 8:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-03 18:41 [PATCH 6.12] netconsole: avoid OOB reads, msg is not nul-terminated Markus Boehme
2026-08-04 1:05 ` Sasha Levin
2026-08-04 8:04 ` Breno Leitao [this message]
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