From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3301B21859D for ; Thu, 8 May 2025 06:00:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746684001; cv=none; b=pH1yyLtvlUDg5uXy/foyJsTpgpSdKIGwe/wFGPvAGucuCdu6qUy3iwSnCrgU8XRSq+Q5q7ppM7u9eCbH5YtdJ2MmAkF+snVMyxhxUn8JixfHqsROE2hHlMzIoyOaaRDEMsWnak7tyllIlELT/89qhqLqW7zm0cjPJ2arVH2ADt0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746684001; c=relaxed/simple; bh=E5d+duO3ltOVFlc1q4h4MDAptrCchoZERkvmIbudXno=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=EBem9jRyUQBhmoOiaPAUcyM8iJkPIMut7MOltE8U7sthCkX1U34LxOkFpcvAMOVT43nYPPmIPFLc97H7FlSeeM/npW6elV33s7Z4wt49HbJHhM1tX2e20v53zVU+kTWImWs6c38pztIwgmn0y17qggvjJhTSjaja8CezPBhOV/g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=NshznGsu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="NshznGsu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C722C4CEEB; Thu, 8 May 2025 06:00:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1746684000; bh=E5d+duO3ltOVFlc1q4h4MDAptrCchoZERkvmIbudXno=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NshznGsuXnibeSmBtW+iybU3woiG100W7Gi8mM/4nuiZW2sA7gnjrMaN3n7E3BtlN tMvEMijLcoToGeA6+EKJg2y8aGdpC1ct6+B9JucckvWMcbe216UswGM62FPsSsfKBo R5IM44bxnzo0v8lVq/762HU3DhC23oN3fyz/gsys= Date: Wed, 7 May 2025 22:59:59 -0700 From: Andrew Morton To: Coiby Xu Cc: Baoquan He , fuqiang wang , Vivek Goyal , Dave Young , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v4] x86/kexec: fix potential cmem->ranges out of bounds Message-Id: <20250507225959.174dd1eed6b0b1354c95a0fd@linux-foundation.org> In-Reply-To: <4de3c2onosr7negqnfhekm4cpbklzmsimgdfv33c52dktqpza5@z5pb34ghz4at> References: <20240108130720.228478-1-fuqiang.wang@easystack.cn> <4de3c2onosr7negqnfhekm4cpbklzmsimgdfv33c52dktqpza5@z5pb34ghz4at> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 8 May 2025 12:25:15 +0800 Coiby Xu wrote: > > > >Acked-by: Baoquan He > > Hi Andrew, > > It seems this patch was missed. January 2024. Yes, it's fair to assume that it was missed ;) > Will you pick it up? Sure. > Without this patch, > kdump kernel will fail to be loaded by the kexec_file_load, > > [ 139.736948] UBSAN: array-index-out-of-bounds in arch/x86/kernel/crash.c:350:25 > [ 139.742360] index 0 is out of range for type 'range [*]' > [ 139.745695] CPU: 0 UID: 0 PID: 5778 Comm: kexec Not tainted 6.15.0-0.rc3.20250425git02ddfb981de8.32.fc43.x86_64 #1 PREEMPT(lazy) > [ 139.745698] Hardware name: Amazon EC2 c5.large/, BIOS 1.0 10/16/2017 > [ 139.745699] Call Trace: > [ 139.745700] > [ 139.745701] dump_stack_lvl+0x5d/0x80 > [ 139.745706] ubsan_epilogue+0x5/0x2b > [ 139.745709] __ubsan_handle_out_of_bounds.cold+0x54/0x59 > [ 139.745711] crash_setup_memmap_entries+0x2d9/0x330 > [ 139.745716] setup_boot_parameters+0xf8/0x6a0 > [ 139.745720] bzImage64_load+0x41b/0x4e0 > [ 139.745722] ? find_next_iomem_res+0x109/0x140 > [ 139.745727] ? locate_mem_hole_callback+0x109/0x170 > [ 139.745737] kimage_file_alloc_init+0x1ef/0x3e0 > [ 139.745740] __do_sys_kexec_file_load+0x180/0x2f0 > [ 139.745742] do_syscall_64+0x7b/0x160 > [ 139.745745] ? do_user_addr_fault+0x21a/0x690 > [ 139.745747] ? exc_page_fault+0x7e/0x1a0 > [ 139.745749] entry_SYSCALL_64_after_hwframe+0x76/0x7e > [ 139.745751] RIP: 0033:0x7f7712c84e4d > Do we know why this has appeared at such a late date? The reporter must be doing something rare. Baoquan, please re-review this? A -stable backport is clearly required. A Fixes: would be nice, but I assume this goes back a long time so it isn't worth spending a lot of time working out when this was introduced. The patch needed a bit of work to apply to current code. I did the below. It compiles. --- a/arch/x86/kernel/crash.c~x86-kexec-fix-potential-cmem-ranges-out-of-bounds +++ a/arch/x86/kernel/crash.c @@ -165,8 +165,18 @@ static struct crash_mem *fill_up_crash_e /* * Exclusion of crash region and/or crashk_low_res may cause * another range split. So add extra two slots here. + * + * Exclusion of low 1M may not cause another range split, because the + * range of exclude is [0, 1M] and the condition for splitting a new + * region is that the start, end parameters are both in a certain + * existing region in cmem and cannot be equal to existing region's + * start or end. Obviously, the start of [0, 1M] cannot meet this + * condition. + * + * But in order to lest the low 1M could be changed in the future, + * (e.g. [stare, 1M]), add a extra slot. */ - nr_ranges += 2; + nr_ranges += 3; cmem = vzalloc(struct_size(cmem, ranges, nr_ranges)); if (!cmem) return NULL; @@ -317,9 +327,16 @@ int crash_setup_memmap_entries(struct ki * split. So use two slots here. */ nr_ranges = 2; - cmem = vzalloc(struct_size(cmem, ranges, nr_ranges)); + /* + * In the current x86 architecture code, the elfheader is always + * allocated at crashk_res.start. But it depends on the allocation + * position of elfheader in crashk_res. To avoid potential out of + * bounds in future, add a extra slot. + */ + cmem = vzalloc(struct_size(cmem, ranges, 2)); if (!cmem) return -ENOMEM; + cmem->max_nr_ranges = 2; cmem->max_nr_ranges = nr_ranges; cmem->nr_ranges = 0; _