From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f51.google.com (mail-ed1-f51.google.com [209.85.208.51]) (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 9746120E4 for ; Tue, 3 Jan 2023 10:15:16 +0000 (UTC) Received: by mail-ed1-f51.google.com with SMTP id u28so38311718edd.10 for ; Tue, 03 Jan 2023 02:15:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=dg4Iem/pwcu+hGrCWyFWcE0w0rA2DwqUcHLBcyuPeUc=; b=mjSbDBWx33CYMdnRAunBxjnUpsQB8NQEfdMQgMgMOMnsSL2cUgoBYVoV1sYAg2p0Zp 50bdUMAQBKLBJKw+RQJGTYGVqDzPzYZoE6hNmGb1i5zXPIqLNykLk0p2pGnXFlik/t2C grRyHKq4PBadLvD2l5ItwXVsIA7HCKuk/+WfMEbq9F2aNiw017v28VGfTtFG/2AijMda veJ+wuzLKcZk3E2ifzeaHUw7UfbUh+7nT4Zs3CJDmhcZ4JEJ4e2YINxHe0YL51HMrGSZ OByncrEr9GdapTEhGBNp8zuujYcX/U+gUYtkegXnSM1hjbSRkh4T4NVSekJxNWP8fRt8 fBhw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=dg4Iem/pwcu+hGrCWyFWcE0w0rA2DwqUcHLBcyuPeUc=; b=VLr+O3yysVqmuGRNMhpMz2/n3FDjghHnyALZ5k0Te5zmshg1MXlQpT73Le20zRZcYi SnXEIP1k28eoR2wDj6Rzrpo4GsjfE4GPV7B+DFA7Jmio6A8gIeuTdxMEz8uS2VL7BoDt FTmg3iggz3Ut1V0ppcQpZYf07CMZo61XC0sVOApy5j4h5dbJnr0AKKedSZxsb3y5O+c5 tEECUdptYbeF5PHGSKNfJKsjyEQRD1Ks+I04mKKWRUHExXIeT0sgW+hIPFET0n7H3FJv l9KFwraxnkNeUjuTZSKrDpcteXLTOM7BDSKJcH1hm+G7LbctE+U9ZJSFG6/Jn9ra35VB iTSg== X-Gm-Message-State: AFqh2koAXBFKmmWAGJNmqglCPRGzPdu5IGMNj5gVIL3flgP8WjPW3C2M 7FepWFgd2Y/75R17A8IJK7s= X-Google-Smtp-Source: AMrXdXvGHahoAqytki6ZL5OVZWOTmKsQ+1eCtyz/+vLkr9dsT6hcqNhYr+klb25nfwe/d8ifvVVIMw== X-Received: by 2002:a05:6402:d5c:b0:461:68e4:15cc with SMTP id ec28-20020a0564020d5c00b0046168e415ccmr34746439edb.9.1672740914735; Tue, 03 Jan 2023 02:15:14 -0800 (PST) Received: from gmail.com (1F2EF380.nat.pool.telekom.hu. [31.46.243.128]) by smtp.gmail.com with ESMTPSA id r7-20020a170906280700b007b27aefc578sm13853448ejc.126.2023.01.03.02.15.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Jan 2023 02:15:14 -0800 (PST) Sender: Ingo Molnar Date: Tue, 3 Jan 2023 11:15:12 +0100 From: Ingo Molnar To: Vlastimil Babka Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Takashi Iwai , x86@kernel.org, "H. Peter Anvin" , patches@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Baoquan He , Dave Young , stable@vger.kernel.org Subject: Re: [PATCH] x86/kexec: fix double vfree of image->elf_headers Message-ID: References: <20230102103917.20987-1-vbabka@suse.cz> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: * Vlastimil Babka wrote: > On 1/2/23 11:39, Vlastimil Babka wrote: > > An investigation of a "Trying to vfree() nonexistent vm area" bug > > occurring in arch_kimage_file_post_load_cleanup() doing a > > vfree(image->elf_headers) in our 5.14-based kernel yielded the following > > double vfree() scenario, also present in mainline: > > > > SYSCALL_DEFINE5(kexec_file_load) > > kimage_file_alloc_init() > > kimage_file_prepare_segments() > > arch_kexec_kernel_image_probe() > > kexec_image_load_default() > > kexec_bzImage64_ops.load() > > bzImage64_load() > > crash_load_segments() > > prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz); > > image->elf_headers = kbuf.buffer; > > ret = kexec_add_buffer(&kbuf); > > if (ret) vfree((void *)image->elf_headers); // first vfree() > > if (ret) kimage_file_post_load_cleanup() > > vfree(image->elf_headers); // second vfree() > > > > AFAICS the scenario is possible since v5.19 commit b3e34a47f989 > > ("x86/kexec: fix memory leak of elf header buffer") that was marked for > > stable and also was backported to our kernel. > > > > Fix the problem by setting the pointer to NULL after the first vfree(). > > Also set elf_headers_sz to 0, as kimage_file_post_load_cleanup() does. > > > > Fixes: b3e34a47f989 ("x86/kexec: fix memory leak of elf header buffer") > > Signed-off-by: Vlastimil Babka > > Cc: Baoquan He > > Cc: Dave Young > > Cc: > > Takashi told me he sent a slightly different fix already in November: > https://lore.kernel.org/all/20221122115122.13937-1-tiwai@suse.de/ > > Seems it wasn't picked up? You might pick his then, as Baoquan acked it, and > it's removing code, not adding it. Thanks, indeed we missed that fix - Boris picked up that version in tip:x86/urgent, via: d00dd2f2645d ("x86/kexec: Fix double-free of elf header buffer") Ingo