From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 336F2C27C79 for ; Wed, 19 Jun 2024 17:52:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B82608D0089; Wed, 19 Jun 2024 13:52:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B32B88D0084; Wed, 19 Jun 2024 13:52:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9FA798D0089; Wed, 19 Jun 2024 13:52:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 819788D0084 for ; Wed, 19 Jun 2024 13:52:51 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 16841813B0 for ; Wed, 19 Jun 2024 17:52:51 +0000 (UTC) X-FDA: 82248383742.27.9590C54 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) by imf30.hostedemail.com (Postfix) with ESMTP id C20B18000E for ; Wed, 19 Jun 2024 17:52:48 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=akoSr2fv; spf=pass (imf30.hostedemail.com: domain of shakeel.butt@linux.dev designates 95.215.58.170 as permitted sender) smtp.mailfrom=shakeel.butt@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1718819562; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=G12t0zsbjBLtka1z3Edmtxikovb2H51+AQMkglEZLGo=; b=MQ9Roey1xzmCcAUEIQjVVmu0SrNl0eCkq5g8I9onyHXD2uH0UqgwMAapJQ3zZtkVYBiNkk jmlMTQg/1cwR/x1vw6aoazaIo2yUqIvTyuFcTzF9CuybGDCAWv5CXPKFt1nSgS+tePVmvc iP8MQRkuri6vrJOdOaa3NgP79RmUzt8= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=akoSr2fv; spf=pass (imf30.hostedemail.com: domain of shakeel.butt@linux.dev designates 95.215.58.170 as permitted sender) smtp.mailfrom=shakeel.butt@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1718819562; a=rsa-sha256; cv=none; b=jTFGR5sepV0+9HRg1KJgLts77cCQVQwWBfq3mZU28oXwUpqd+xrbeT3l5mW9vhW3JVG0JY nBHNc1auSpgpb6zMuEGUi9z99TDhg2WaYOAdW/pzfX+HG1Upx1ASXr1b529vkNDUg+2K9A mSSi6FFYY/8B0K+oNS11/d3VZprttN4= X-Envelope-To: mjguzik@gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1718819566; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=G12t0zsbjBLtka1z3Edmtxikovb2H51+AQMkglEZLGo=; b=akoSr2fvU73Q0cSewLCqxsWHjT3wWMthQ4WH14GMMUiok98sXGU8Y/gQX9C04DwYpcgDOv Z1Y1GlEg3tyfD1OtiM2DOaf144Zxdcetx7jXL3Ov7cTn47wfrqCsNAf72CC3HSpXkqGafg Ih6uyJ8AqFVjMuTPlbjqniF38dZZoBw= X-Envelope-To: akpm@linux-foundation.org X-Envelope-To: mhocko@kernel.org X-Envelope-To: torvalds@linux-foundation.org X-Envelope-To: kernel-team@meta.com X-Envelope-To: linux-mm@kvack.org X-Envelope-To: linux-kernel@vger.kernel.org X-Envelope-To: kyle@infradead.org Date: Wed, 19 Jun 2024 10:52:41 -0700 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Shakeel Butt To: Mateusz Guzik Cc: Andrew Morton , Michal Hocko , Linus Torvalds , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kyle McMartin Subject: Re: [PATCH] mm: ratelimit oversized kvmalloc warnings instead of once Message-ID: <20240619175241.6i5fjkjm3sl4aaas@linux.dev> References: <20240618213421.282381-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Stat-Signature: sc89oxjfensusmjmiy1a373rrqyhgyo4 X-Rspam-User: X-Rspamd-Queue-Id: C20B18000E X-Rspamd-Server: rspam02 X-HE-Tag: 1718819568-27127 X-HE-Meta: U2FsdGVkX1+P+Fj4Nrw3uWv2WzhBt5oz9o5TVwf48162JFnxp4Lve9P+A4EDM4RHQYs2k0UeQoP5+T+pf1n259cokllya2+UgkSoMEj+sO0aEN+xJAN+2vlBXP85DC32JODgFA328DaX6eE8r2Miw0QdK5LrKOtVpRMRD7azcbqYGwH+CqdisZHzzNP/aGvDOeWh6zbevkoR4AuixlLaOWYBSs9ojOAmRrIwS5S3knSPtf3NGNOOfojzVRrO8bmtJujA/P4S0sq3ssoKV1NnuMAgYsWZeZwtYHqyni3nKiT/M7N9LGwfg0ENdXswqi7ICM+c3YIk/fbUFrR72LO85U6gjHUGMIhEU49lyU1HMSm/n1N73AKrCXXgmk/woygM+Nh2V1Uk3oqp5WduzqQS8C1N2QF0knRh3wmmTGYFdmt+Dx2NaclWy4Kon7VxBwtynj2iamNZ58VJn2GRkO8LmsMqhB4eRU9sqHJ64qFdDPph1ToHwjly1JpKNNdcTmfEkKrRd9VQlriJJYEaW9cobrFyc2/yxyzNBDyie4Vy9XNtLcgd2XZu4uFUTzNWJuJkTDnL1xe7lDynQ2pXVlQZhQWEPH3IqFKgRnmCGL28AOQuvQZlGp73iaIgUvzaMWmNujwY+v6KSvePDpPLKTTye5QYYEDic0cTTla4ZmrW7N9OMNStoLeUNZzAgkgnoaBuuspXu22duMEtF0N1x0gxphjbDbgfeRMvEAXdxanr6Y73cj92uvnY/LS8E8ChVqUrRWf7XI+yYkxSwVUciCAy5xARfYMs9b/du2vZ2phhZ0Yddr9ZPj8tWojDw1YMr0JdeaEzwsS7XOPNgLE+A8XCkVRRQk2g34JVCCiXIfo/nZN7xajZvowB45r6aev6AxvKqapMlxvAcB91pMaAMADNQuZh+QIDfDHyh9da0InE1VhNnDKo9Bhr5vft89hG9Qu6hMyeZ4EWN+EIUdCCX0e Et3c51WI 538neKmuQvysHLwNboE0y91g8g9Uldc6CYX1BJAhP6QRdc28FPPnAwYKrpPHhS5GwjPHbspWUGj8ieq+wgM/yJd8383e+W7m+pE1iSeUwZuYtnFQPVPNFaozWtP2c8l1o+xBuNihOvAH357N5bbaZ26RyrTGSvyHulhmL8s7bqxnNEYibbcq7CSo5rQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jun 19, 2024 at 02:49:21PM +0200, Mateusz Guzik wrote: > On Tue, Jun 18, 2024 at 02:34:21PM -0700, Shakeel Butt wrote: > > At the moment oversize kvmalloc warnings are triggered once using > > WARN_ON_ONCE() macro. One issue with this approach is that it only > > detects the first abuser and then ignores the remaining abusers which > > complicates detecting all such abusers in a timely manner. The situation > > becomes worse when the repro has low probability and requires production > > traffic and thus require large set of machines to find such abusers. In > > Mera production, this warn once is slowing down the detection of these > > abusers. Simply replace WARN_ON_ONCE with WARN_RATELIMIT. > > > > Reported-by: Kyle McMartin > > Signed-off-by: Shakeel Butt > > --- > > mm/util.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/util.c b/mm/util.c > > index 10f215985fe5..de36344e8d53 100644 > > --- a/mm/util.c > > +++ b/mm/util.c > > @@ -649,7 +649,8 @@ void *kvmalloc_node_noprof(size_t size, gfp_t flags, int node) > > > > /* Don't even allow crazy sizes */ > > if (unlikely(size > INT_MAX)) { > > - WARN_ON_ONCE(!(flags & __GFP_NOWARN)); > > + WARN_RATELIMIT(!(flags & __GFP_NOWARN), "size = %zu > INT_MAX", > > + size); > > return NULL; > > } > > > > I don't think this is necessary. From the description I think interested > parties can get away with bpftrace. > > Suppose you have an abuser of the sort and you are worried there is more > than one. > > Then this one-liner will catch *all* of them, not just the ones which > were "lucky" to get logged with ratelimit: > bpftrace -e 'kprobe:kvmalloc_node_noprof /arg0 > 2147483647/ { @[kstack()] = count(); }' > > Of course adding a probe is not free, but then again kvmalloc should not > be used often to begin with so I doubt it is going to have material > impact in terms of performance. > > While I concede it takes more effort to get this running on all affected > machines, the result is much better than mere ratelimit. Also there is > no need to patch the kernel. > Thanks for the response and suggestion. I am inclined towards warn once for each unique stack trace as suggested by Michal because I think it would be useful in general.