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([103.172.182.26]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-36141990bb6sm87274a91.17.2026.04.16.18.16.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Apr 2026 18:16:17 -0700 (PDT) From: ZhengYuan Huang To: akpm@linux-foundation.org, david@kernel.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, ZhengYuan Huang Subject: [PATCH] mm: prepare anon_vma before swapin rmap Date: Fri, 17 Apr 2026 09:16:06 +0800 Message-ID: <20260417011606.1089985-1-gality369@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: D7204A000C X-Stat-Signature: wqmd1wwd7qs17iwxu1daoxpma3a7uzc9 X-Rspam-User: X-HE-Tag: 1776388579-75791 X-HE-Meta: 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 +y29/LoF j7MQwL2VAyyWHw6qyGuT8vgv9kVWi6rpMRrCAUcXo2umR7AjtLLXpJnlXPjofbkt0ArOooufun3tpTwS6oLOhxuM1UppKM938o1eNnygq4Zwd545Nb41NX78Kc/J/Kg6FMEQsWKF+9K/IWDSAo0qhN0noAtpnZxZZ7xIqR7N/5x59r2RSxookEjnDC3J5ixRfEsFXBxiIrAsRSzki4g6B8XFqT1NWrb4Q4lfgmXXGbAbe+OCUckRBsTjGMs31e8oTdFS+sakC4F0EEgVoiuYid5NDmOFaVlvYGCQvy2X4gPIGVMpdTQ7Ti4RHAB09B/SiaZpltGqV/GQvJ4C9QZ10cPOXQ7oB5HAzSTBimta1QciGZH99vSfAf16d/byidPTcOTj/PBYa/uRzhIQ+r3NzKqmf7RK4JlX2kicBpXxyH16mIRCi4YSjj4UEtwMj6m2CP52wXYA0lK98PnE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: [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(), while __folio_set_anon() still BUG_ONs if vma->anon_vma is NULL. So although I could not reproduce the issue on next-20260415, I also could not confirm that it has been fixed there. Recent changes around the swap fault path may have affected the reproduction conditions, but I may also be missing another relevant change. --- mm/memory.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index ea6568571131..a64bc9826cc5 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4850,6 +4850,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) goto out; } + /* Swapin installs anonymous rmap state into the faulting VMA. */ + ret = vmf_anon_prepare(vmf); + if (ret) + goto out; + /* Prevent swapoff from happening to us. */ si = get_swap_device(entry); if (unlikely(!si)) -- 2.49.0