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 6DF3B39C01D for ; Thu, 23 Apr 2026 10:38:34 +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=1776940714; cv=none; b=HlrZM89Mg8JRrp6DsNVb0qQrdyOWQrbLqYR6GVTKkuCOVgo7qq/zj81DGeXZgYbdw/U2dZac08RwW+ITylfb6qxdvdZguzCZTJbGtNvud+n9xr0qDpb+7Fx9qf7HWg8mgw0leYoMXw2RZ0pVm13vkpRUSvtZ8otTgaPp5B/uz7o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776940714; c=relaxed/simple; bh=OykCGngjeVXxh+S5FhihKYrlA0mMJyXZVqRb3yjbltQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nfkCL0OjpW6bzVR1TPZ+0dZoYShffMQZu6cYGChHdpyLYTr1xr/4HcUMb717DU9UgOOLBlQVhlkNIGs1A7YKoJWcNSDypfw5Ue2nmm5uu2TVaOgRjlW2CcR3E3Kqtl/PgLwQB8inbtSzXSbOeuifKl2DQ2+NhXcSIHM82fmrFaE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NOGs+0Jr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NOGs+0Jr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 206FFC2BCAF; Thu, 23 Apr 2026 10:38:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776940714; bh=OykCGngjeVXxh+S5FhihKYrlA0mMJyXZVqRb3yjbltQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=NOGs+0JrJ4V2SyqOjrtFCQhLPr6YNzdn9bI3as6PXFB7UQwCHKiLnzRPHyEUcB7ZN VKGOTXW/gkIMWlDZFdEi6oECp+yHwo4lAx3NokhIMuokGolZjyGr/nsVX3mbl/27Vo v7/vhuCEqkUK7uPz7wPEiT6mcRIUBnH2DMkpiEu/tktjWePw9DsAs0KodWlI72iVDz H0ITnKBGxvzcxasSWRZcfAXV5DGRFsTtMbzeNb5VyCC7xt43PWdQ0Qj1iPKl7saBqy 3FJRdZzjsfdBx5KUS9/me1V0pBiumh481fCG5n7UpmfcuKvquCsHIESxS8bpeMWIdr KGrBrssiZK2cA== Message-ID: Date: Thu, 23 Apr 2026 12:38:27 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 v5 2/6] mm/memory_hotplug: Fix incorrect altmap passing in error path To: Muchun Song , Andrew Morton , Muchun Song , Oscar Salvador , Michael Ellerman , Madhavan Srinivasan Cc: Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20260423071911.1962859-1-songmuchun@bytedance.com> <20260423071911.1962859-3-songmuchun@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260423071911.1962859-3-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/23/26 09:19, Muchun Song wrote: > In create_altmaps_and_memory_blocks(), when arch_add_memory() succeeds > with memmap_on_memory enabled, the vmemmap pages are allocated from > params.altmap. If create_memory_block_devices() subsequently fails, the > error path calls arch_remove_memory() with a NULL altmap instead of > params.altmap. > > This is a bug that could lead to memory corruption. Since altmap is > NULL, vmemmap_free() falls back to freeing the vmemmap pages into the > system buddy allocator via free_pages() instead of the altmap. > arch_remove_memory() then immediately destroys the physical linear > mapping for this memory. This injects unowned pages into the buddy > allocator, causing machine checks or memory corruption if the system > later attempts to allocate and use those freed pages. > > Fix this by passing params.altmap to arch_remove_memory() in the error > path. > > Fixes: 6b8f0798b85a ("mm/memory_hotplug: split memmap_on_memory requests across memblocks") > Signed-off-by: Muchun Song > --- > mm/memory_hotplug.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 2a943ec57c85..0bad2aed2bde 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1468,7 +1468,7 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group, > ret = create_memory_block_devices(cur_start, memblock_size, nid, > params.altmap, group); > if (ret) { > - arch_remove_memory(cur_start, memblock_size, NULL); > + arch_remove_memory(cur_start, memblock_size, params.altmap); > kfree(params.altmap); > goto out; > } Yeah, that's nasty. We should CC stable. Acked-by: David Hildenbrand (Arm) Should we extend the safety checks we already have on the other path? diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 2a943ec57c85..1c304468af08 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1402,6 +1402,12 @@ bool mhp_supports_memmap_on_memory(void) } EXPORT_SYMBOL_GPL(mhp_supports_memmap_on_memory); +static void altmap_free(struct vmemmap_altmap *altmap) +{ + WARN(altmap->alloc, "Altmap not fully unmapped"); + kfree(altmap); +} + static void remove_memory_blocks_and_altmaps(u64 start, u64 size) { unsigned long memblock_size = memory_block_size_bytes(); @@ -1426,10 +1432,7 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size) remove_memory_block_devices(cur_start, memblock_size); arch_remove_memory(cur_start, memblock_size, altmap); - - /* Verify that all vmemmap pages have actually been freed. */ - WARN(altmap->alloc, "Altmap not fully unmapped"); - kfree(altmap); + altmap_free(altmap); } } @@ -1460,7 +1463,7 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group, /* call arch's memory hotadd */ ret = arch_add_memory(nid, cur_start, memblock_size, ¶ms); if (ret < 0) { - kfree(params.altmap); + altmap_free(params.altmap); goto out; } @@ -1469,13 +1472,12 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group, params.altmap, group); if (ret) { arch_remove_memory(cur_start, memblock_size, NULL); - kfree(params.altmap); + altmap_free(params.altmap); goto out; } } return 0; -out: if (ret && cur_start != start) remove_memory_blocks_and_altmaps(start, cur_start - start); return ret; Maybe the helper should even go into altmap code? Not sure. -- Cheers, David