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[209.85.220.65]) by mx.google.com with SMTPS id s65sor665850pfb.30.2019.06.06.18.57.41 for (Google Transport Security); Thu, 06 Jun 2019 18:57:41 -0700 (PDT) Received-SPF: pass (google.com: domain of yury.norov@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=JKvNpstA; spf=pass (google.com: domain of yury.norov@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=yury.norov@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=fMmuJCA3LCdg91iSc6/9qeFXRSKlknMhuRfQX7ASOjc=; b=JKvNpstAHFdgappvoFZTSBTYlIL3/rZ47hg8HWoFbIEqVkiV0EhBBZRLRpyoICFyrS ClCg438cs5YejBJpHXQckK0pyK/nX11Mbv0+5nKGWykE5lZ3jpOuxeVRFnlLKbW87lcG bewtkILSMTIQJO7EetY0lF6sRJUs+8uhC1RbETeTx8z2OBcWkDlJX8xMnfs/FngxD9je npdlOr57+ayjx56h+5W94hdtUiDJMVs9Pyj5fGRTYXGLjXwkFhCFeOws4+ZwA/7nmOcz UYma0uNuuj6tU25IwM5aMXHiCF1uwqjvpSLHw6IOmKy/ZVxAahFu17CHyfSoUMsaCxjk DrJQ== X-Google-Smtp-Source: APXvYqzOGmPQ+4bSZiqeJZcCwiv/ZjmMksHt7GIGid5GMzyY0FfrS/4RyF2iuz/q9m86aoMdGrLu4w== X-Received: by 2002:aa7:9256:: with SMTP id 22mr43149580pfp.69.1559872660804; Thu, 06 Jun 2019 18:57:40 -0700 (PDT) Received: from localhost ([2601:648:8300:77e8:e0fc:fdfa:3d2e:ab5a]) by smtp.gmail.com with ESMTPSA id 85sm408342pgb.52.2019.06.06.18.57.38 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 06 Jun 2019 18:57:39 -0700 (PDT) Date: Thu, 6 Jun 2019 18:57:37 -0700 From: Yury Norov To: Qian Cai , g@yury-thinkpad.kvack.org Cc: Yuri Norov , Andrey Konovalov , "linux-kernel@vger.kernel.org" , Andy Shevchenko , Andrew Morton , "linux-mm@kvack.org" Subject: Re: "lib: rework bitmap_parse()" triggers invalid access errors Message-ID: <20190607015737.GA11592@yury-thinkpad> References: <1559242868.6132.35.camel@lca.pw> <1559672593.6132.44.camel@lca.pw> <1559837386.6132.47.camel@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1559837386.6132.47.camel@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 06, 2019 at 12:09:46PM -0400, Qian Cai wrote: > On Wed, 2019-06-05 at 08:01 +0000, Yuri Norov wrote: > > (Sorry for top-posting) > > > > I can reproduce this on next-20190604. Is it new trace, or like one you've > > posted before? > > Same thing, "nbits" causes an invalid access. > > # ./scripts/faddr2line vmlinux bitmap_parse+0x20c/0x2d8 > bitmap_parse+0x20c/0x2d8: > __bitmap_clear at lib/bitmap.c:280 > (inlined by) bitmap_clear at include/linux/bitmap.h:390 > (inlined by) bitmap_parse at lib/bitmap.c:662 > > This line, > > while (len - bits_to_clear >= 0) { [...] The problem is in my code, and the fix is: diff --git a/lib/bitmap.c b/lib/bitmap.c index ebcf4700ebed..6b3e921f4e91 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -664,7 +664,7 @@ int bitmap_parse(const char *start, unsigned int buflen, unset_bit = (BITS_TO_U32(nmaskbits) - chunks) * 32; if (unset_bit < nmaskbits) { - bitmap_clear(maskp, unset_bit, nmaskbits); + bitmap_clear(maskp, unset_bit, nmaskbits - unset_bit); return 0; } I'll add a test for this case and submit v3 soon. Yury