From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-il1-f200.google.com (mail-il1-f200.google.com [209.85.166.200]) (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 33DED3A294 for ; Mon, 12 Feb 2024 13:28:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707744518; cv=none; b=eqCxgxFGtoF/F77X4T1bpXs44ipg7WwFjJTO6cilpK2HnSkbHlov80mcYDIQl4CMPDd+6XF0zkskmAqQM+sMS8xv5FcrLmHwP8YUyBM61gDYuUE4Amt1v8+GLbhsaXH9NondRO+agfVJnyzcHGQLumEIXgQUFpneVp+SdeRuX9A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707744518; c=relaxed/simple; bh=f73SHcPfM2QhZLAtN0ksmvdhsF8obYYxUIXVCxv/EAI=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To:Cc: Content-Type; b=Nq7tdg9Al7CSeNkF8M2bGlEq4T7v0QfhKfco+zXGNONSw0BEDXJeprNFce5yh09c2fKYgForRT0eu28Lp3NsJDyAHFGB5hTYpWKyOOFxPTZYP2gjkrX66csgcfX8qGhZ8BoQQClPyRneBPgXok+A3tC4ytnfshoZJv/IQYb4chI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.166.200 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-il1-f200.google.com with SMTP id e9e14a558f8ab-363d86bef43so17482025ab.0 for ; Mon, 12 Feb 2024 05:28:36 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707744516; x=1708349316; h=cc:to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ObKSC16eAptSqU30mun4surYToSSq3dApxjAL/tX6gw=; b=iQb/5BKN1Uhnz6FJ7Bm5TIRxFhUwE3qDAX87uB/y9oYk2jLGvTEVfSBEg0NqMQp6da qliDZVNf6sXptMo0tiNqDqRZaqOZmbKS7H9htOJ8UZ1XZvDzr3mdnJI/cr1FFoZa967K z6d1CbtwXvM4mfhkwYncfsN+ej80SKohEnFwnMgIjyK5e35wrTS717OV0vwHm1A+vJ1F /tQF+sVZxrXnjttpNlejM4M0y9LG9yb1KYsNupwuPvGWBkOn65pOVz61DvWEzCsdK0qq 8z9VbjY7oiEM7uxe4mTUdjCSBux25oq8jh1PKNmzUzDsUry002td1wm7MV9NhWYay90y zK/g== X-Forwarded-Encrypted: i=1; AJvYcCW/k0Gse+pEQuKT5eyW/QRfL4sJR9Fk2WqYoOg7jqdH8WF6w8x5fY7OSpyazOdqWFnWQ3EdvXLwzhC/03qx39pCQk1ydchx X-Gm-Message-State: AOJu0YzoLNLUCjBXipuAFnCNKLcdRDPVpkvt6fulgqa9tR+3TcaA99d6 wpAKLAOELQa6OJ+moe7gtQVOs8G5c14dST8kEnQbhFM332pHBzaTZfEUf+Y+W6i4MRD71QzmW/Q mHq0P+BDUhSgst8K7Q+4YYecbPaY6PeBkmpYauJq2t1vR1Wyyr5CF358= X-Google-Smtp-Source: AGHT+IHfkrFFxnp5qczPid0DMB6lHfZKxsUkP/JbTv6q6YSpbuczYG9H2u4I3KdB22kZsZNI292eWhtMsSwySB1BsAlvWTGzM3qO Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6e02:12c7:b0:363:7b86:21bd with SMTP id i7-20020a056e0212c700b003637b8621bdmr612673ilm.4.1707744516291; Mon, 12 Feb 2024 05:28:36 -0800 (PST) Date: Mon, 12 Feb 2024 05:28:36 -0800 In-Reply-To: <3281463.44csPzL39Z@ripper> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <00000000000042c47206112f4123@google.com> Subject: Re: [syzbot] [batman?] BUG: soft lockup in sys_sendmsg From: syzbot To: sven@narfation.org Cc: a@unstable.cc, b.a.t.m.a.n@lists.open-mesh.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, linux-kernel@vger.kernel.org, mareklindner@neomailbox.ch, netdev@vger.kernel.org, pabeni@redhat.com, sven@narfation.org, sw@simonwunderlich.de, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" > On Monday, 12 February 2024 11:26:24 CET syzbot wrote: >> syzbot found the following issue on: >> >> HEAD commit: 41bccc98fb79 Linux 6.8-rc2 >> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci >> console output: https://syzkaller.appspot.com/x/log.txt?x=14200118180000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=451a1e62b11ea4a6 >> dashboard link: https://syzkaller.appspot.com/bug?extid=a6a4b5bb3da165594cff >> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 >> userspace arch: arm64 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/0772069e29cf/disk-41bccc98.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/659d3f0755b7/vmlinux-41bccc98.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/7780a45c3e51/Image-41bccc98.gz.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+a6a4b5bb3da165594cff@syzkaller.appspotmail.com >> > > #syz test This crash does not have a reproducer. I cannot test it. > > From 5984ace8f8df7cf8d6f98ded0eebe7d962028992 Mon Sep 17 00:00:00 2001 > From: Sven Eckelmann > Date: Mon, 12 Feb 2024 13:10:33 +0100 > Subject: [PATCH] batman-adv: Avoid infinite loop trying to resize local TT > > If the MTU of one of an attached interface becomes too small to transmit > the local translation table then it must be resized to fit inside all > fragments (when enabled) or a single packet. > > But if the MTU becomes too low to transmit even the header + the VLAN > specific part then the resizing of the local TT will never succeed. This > can for example happen when the usable space is 110 bytes and 11 VLANs are > on top of batman-adv. In this case, at least 116 byte would be needed. > There will just be an endless spam of > > batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (110) > > in the log but the function will never finish. Problem here is that the > timeout will be halved in each step and will then stagnate at 0 and > therefore never be able to reduce the table even more. > > There are other scenarios possible with a similar result. The number of > BATADV_TT_CLIENT_NOPURGE entries in the local TT can for example be too > high to fit inside a packet. Such a scenario can therefore happen also with > only a single VLAN + 7 non-purgable addresses - requiring at least 120 > bytes. > > While this should be handled proactively when: > > * interface with too low MTU is added > * VLAN is added > * non-purgeable local mac is added > * MTU of an attached interface is reduced > * fragmentation setting gets disabled (which most likely requires dropping > attached interfaces) > > not all of these scenarios can be prevented because batman-adv is only > consuming events without the the possibility to prevent these actions > (non-purgable MAC address added, MTU of an attached interface is reduced). > It is therefore necessary to also make sure that the code is able to handle > also the situations when there were already incompatible system > configurations present. > > Cc: stable@vger.kernel.org > Fixes: a19d3d85e1b8 ("batman-adv: limit local translation table max size") > Reported-by: syzbot+a6a4b5bb3da165594cff@syzkaller.appspotmail.com > Signed-off-by: Sven Eckelmann > --- > net/batman-adv/translation-table.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c > index b95c36765d04..2243cec18ecc 100644 > --- a/net/batman-adv/translation-table.c > +++ b/net/batman-adv/translation-table.c > @@ -3948,7 +3948,7 @@ void batadv_tt_local_resize_to_mtu(struct net_device *soft_iface) > > spin_lock_bh(&bat_priv->tt.commit_lock); > > - while (true) { > + while (timeout) { > table_size = batadv_tt_local_table_transmit_size(bat_priv); > if (packet_size_max >= table_size) > break; > -- > 2.39.2 >