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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776423223; bh=Q4iAYpxOXsLj0oOnh+Wyu8n4Jy+Sax3z4g38z+Vd71Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=kiRbc4j0nRxXmu6WAUKM5hJlpAnDjDep590MNd/jAnob9geMeFguPI2hM4b81LTzx qHeN01mxoVcke3G0RhF5gC72xk2bp5Ur9kE/ssQFLeW06NgJL/EMJCTPaOvYoMEhpT zEhOgwmKOIx7eDjuSyoM6M48g8xGniE/uNakksHOD4eC2Q8dZd4pupuiNrkSO9NuXl sMqM8Zd6gc6eAUAFlk9jDKd24m9P+AYRR2124+UaMCmHiykTBMKHBjck8WlgEDM1WS QvmPmgOcek9lnyUO+8SP6TK7KdbYfrudgu/nOAlDt9FRYrfYFNLtMoarD2O0dLpUWk s+9YE0om4kxoA== Message-ID: <66f67e51-819b-4c60-9f61-170db32362a2@kernel.org> Date: Fri, 17 Apr 2026 12:53:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: prepare anon_vma before swapin rmap To: ZhengYuan Huang , akpm@linux-foundation.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, willy@infradead.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, r33s3n6@gmail.com, zzzccc427@gmail.com References: <20260417011606.1089985-1-gality369@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Stat-Signature: dz45qffsxcx9qmbucn4iqbpgjkzun7rz X-Rspam-User: X-Rspamd-Queue-Id: 2168918000D X-HE-Tag: 1776423223-756349 X-HE-Meta: U2FsdGVkX1/3ZZPgf9jDVxYOP/eqYHtzWMr0N0No1iULm8K4AB4QV97BuMJ7cp1Q+yz1a1KBkDW56ydChA2SuZEyxNl7XGoW+VoK2thlP847N+br2g29KiPyzEHpsw5u7guJoo57pPjSKi+N2F7C88CFy78J9PyciX7ZY/uSzsbUg4tpRN4HCavwaf/YM+Ip9EqhCYeJqhzmrtMidMUPP/VG851FphornPzIFNZgdi5j+rwQh7eABU2nmhyu4qJ/6XA3LZcAF5teYni06Gcb/sQQabCSXqIHlcX9Ygo9qP8kCXPtl7TdU4KyhTNR3DRr4WZCl7IC5GbJGOPtGeqM3dzTqG/QUya14ip/DigPq2kGgzlT8u5YfOygGmKZAnxEk/KBv22je0S9nrdIHswv1HXQiX0XNX9fHiFVhSrwvn+mh0KaSPfFPXqEdHjJkhxOJR+G2uTZfzKtqFNE32TqNcf0vANy3FxfTZO2FL2NaKbijI+ashFyhzUces/AFv4JtphlY4a6yuGGRaDU5U6W+xzJ5SEucFTcnMzjPsAA+jqzI9z7aTUy+czCGDAmYbuaY1atzqLTJzsZksCO2vVKfr5vGcpCi3EaWB2IackElHxlxf0k+NG5DFWQl6Q30RkldPk/zkmY4tGX2LPZerjUosYGudc625yCYX3/V1FEkAjQgxTizFCrfr5Z3fk5W2A33ZfWec7qpF4JQ3Zv6IXUy026VBN2TbCHNVozaeReLgujmKZqojvi6wtEQPEMte7DDbrUlqy/uav/z7wKpde/VcBRxiU3jGKfjNFZ8uxIAafgkM9b3rDQhLRua9/eq4DhGmb4prXDW8vqkxtOTqKZD1nrrRdozEicYY9o5m/d63HhDldetGK7A/nBk87D6jQtyD6K5h0nzP2PnRagleENqMEK7rsWlxxVloGNOwmkjA1uUwhjVUEkCMZgMKTbN4jDeoYIbSlu1e74wad22Qc XfNH+Bxd /fmbrDhtYzMpQWWDotz/slmo7kJ7eddspR6s1Qd0b1R7eNCEpRn+zCUy77Suz8yrGENnEtuPiSs6HCRjyzqzd5ZuPK9bbE5kNficZKyo2iIxvrSZpxcNrsT5N6izgrQHnT55XxuvUXRMDx52Cepjt6KyYOtVv8K/ttpuW2TJQ0LK7wM3XMXk2rgRC7F6lbbYNZe8JfgCD/T4AGr+aD+VxRwzkxHrmvj+q48lxY6J7owD4jY6oIkacitTXBMorhizWAVpbyvA2HEVA2kNLBLTiz0Z8D3FJzrdmc4XRnmQK6pcP/+QnsuOj5dp22XSFIg7Z0lFHX/tw5We1nGo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/17/26 03:16, ZhengYuan Huang wrote: > [BUG] > madvise(MADV_HWPOISON) can fault a swap entry back in through > get_user_pages_fast() and hit: > > kernel BUG at mm/rmap.c:1364! > Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI > RIP: 0010:__folio_set_anon mm/rmap.c:1364 [inline] > RIP: 0010:folio_add_new_anon_rmap+0x41d/0xc10 mm/rmap.c:1553 > Call Trace: > do_swap_page+0x14c5/0x5c30 mm/memory.c:4963 > handle_pte_fault mm/memory.c:6198 [inline] > __handle_mm_fault+0x1512/0x22f0 mm/memory.c:6336 > handle_mm_fault+0x42f/0x820 mm/memory.c:6505 > faultin_page mm/gup.c:1126 [inline] > __get_user_pages+0x4b3/0x3400 mm/gup.c:1428 > __get_user_pages_locked mm/gup.c:1692 [inline] > __gup_longterm_locked+0x945/0x14b0 mm/gup.c:2476 > gup_fast_fallback+0x8a3/0x2440 mm/gup.c:3220 > get_user_pages_fast+0x64/0xb0 mm/gup.c:3298 > madvise_inject_error mm/madvise.c:1456 [inline] > madvise_do_behavior+0x503/0x860 mm/madvise.c:1875 > do_madvise+0x17e/0x210 mm/madvise.c:1978 > __do_sys_madvise mm/madvise.c:1987 [inline] > __se_sys_madvise mm/madvise.c:1985 [inline] > __x64_sys_madvise+0xae/0x120 mm/madvise.c:1985 > ... > > [CAUSE] > Commit a373baed5a9d ("mm: delay the check for a NULL anon_vma") moved > anon_vma preparation out of the generic fault path and into the fault > handlers that actually need to install anonymous rmap state. > > do_swap_page() was left behind. It can still restore anonymous mappings > via folio_add_new_anon_rmap() or folio_add_anon_rmap_ptes(), but it does > not call vmf_anon_prepare() first. On a VMA-lock fault this can leave > vma->anon_vma NULL all the way down to __folio_set_anon(), which BUG_ONs > on that violated invariant. > > [FIX] > Prepare the faulting VMA's anon_vma once do_swap_page() has confirmed it > is handling a real swap entry, before any swapin path can install > anonymous rmap state. > > vmf_anon_prepare() already handles the retry rules for VMA-lock faults, > and when anon_vma is already present this stays a single likely branch in > the swap fault hot path. > > Fixes: a373baed5a9d ("mm: delay the check for a NULL anon_vma") > Signed-off-by: ZhengYuan Huang > --- > I can reproduce this issue deterministically on v6.18, but I have not > been able to reproduce it with the same setup on next-20260415. > > However, I have not identified a change that clearly explains the > difference. From code inspection, do_swap_page() still appears able to > reach folio_add_new_anon_rmap()/folio_add_anon_rmap_ptes() without a > prior vmf_anon_prepare() If there is an anon page swapped out, certainly at the allocation time of that anon folio, there would have to be a anon_rmap allocated. During fork, the anon_rmap would have to be created as well. Something is off here. -- Cheers, David