From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) (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 A39DC1E5B68 for ; Sat, 15 Aug 2026 05:20:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786771205; cv=none; b=PKoYCxQet4FCXeUYo4IY6IARKSm1fWyKUEXJ54Ht/EuiYwaJ9p6eTZy+sDBeQGCgg0QSh4/3pbMN31P+jHpEhSJSMvsOg8SPAdi5LJKJidN76wPAPjzmcG7n4kg6zhb9CrIRL3FmrDLuxz7PvNV3GNIiDSDdzzoC6+XGw/8y3N8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786771205; c=relaxed/simple; bh=2r1RF881LYsHVlBEr4htWYzA6gwwa9pnKcUsZN5CSdE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uxbe4sjZ9vji12k69GMuH0jADB+8JmE5KhvlFzvvxGmrmYfB14NodTTrEXPpZgffcfKf9fk0+78jrTCgS0NT2gI/WYnfrF83i4YN5UCNRUSZOrhpPODv2awrPWUDNr9mumw+5/XTYomhiNqy2fdeS21eVAiL+n7VZBkSuY96gh4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=XpppSY+S; arc=none smtp.client-ip=209.85.216.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="XpppSY+S" Received: by mail-pj1-f47.google.com with SMTP id 98e67ed59e1d1-3811f512167so2482503a91.3 for ; Fri, 14 Aug 2026 22:20:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1786771204; x=1787376004; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=/yDUp3cp/r1Pc+NMXZTiNUemFBBGGof6Vn7/JKGoQAI=; b=XpppSY+SwcweMS6++TdSfy0vRvVfPfk0bqIKbTf/VMyuacUDz4eTB4IavWfpjq85EV 99mHD2Fl1z5AgAOdSPhHygGPoKPvK0c6q73PYKLVkyz3YXRzsVafzxuhp4FA8SWiyYq7 Hzg+nRSPEn/l/I1ndlvUFAMzo+HDiupEeBia6mGI1u+GNbsUUGDDL4uddU/SuxY0geWd MWsmIsQA955yk2Y1Ycy8XQa0n8s0lt812q2GortHv5oS2G6D6E8Xtri9SQ/utIG5tueH zD/HKj98BB625OMle7i6vgix19ZlyBeHVTiUlR08VbuhLywbTirrs7OZbEAsqVr/HC4G 06/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786771204; x=1787376004; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=/yDUp3cp/r1Pc+NMXZTiNUemFBBGGof6Vn7/JKGoQAI=; b=O2Ihdz4AYzTngPoazUPhW1+9pqkkgUvDZOPZIaDrGO9CWxsz3/062HtzxAaGXEt8J0 pKqu9AV2FYe3RisErGzXpMpFzZVNX20FDQURujcu5lyULwdaftYE2pZDwIA7YRA2d6Ps rNHIW07zxH1xe2Jae4KkAHRyZZljisYufndbXkP0bd8bV4Xk6gAeT6T8rUni2gYVFmn8 sy1/BB/8D0LXTv6e4ymzBBMVPymS6IgkCXQHKQCQkucjG8Iji3iStVZJN6tMScvFC9Rd jwPBZ/8qox4rXKa00/xmyudpRQyAkBEg4gp7wb5IlT/jYBAa5jWJM0wEkE7rGTXNZOI0 30qA== X-Forwarded-Encrypted: i=1; AHgh+RqwJum/mAhZa5thThTOv5lSL1k2eLz2mktvpnn0DqDkGvDok9qE2/YpMcXdarNgpnMz+K7SAL3KJ+eCiDc=@vger.kernel.org X-Gm-Message-State: AOJu0YwjFECBsTogQxfT0cK4hY+Q6KQQqQzNph4g21UakcNT95OTYc8W feOdmgynljY3hwSqkU4cBIyZZJ7g7fiSdzKY1dPUgpNwS8DQEDkyu2oA X-Gm-Gg: AR+sD10dKEsudGg0zzagH1IjnjY8OdVUL63UzJPqXBdVqu3TnmXUXnZY/m0U8gEqzBU vXQbIyFmIo9slB9+a/ZUNlrN+bEiwsFYeSsocyjQD6TSfZ1J8VP/JpHIc6YGjND44YAZbSipBoJ rHqAVeTf3XmSAxo6e0VWSuYqiHUdGX9bZuUs4W9hXprMSG20AuaKgUEQcoLoKgx8qr+xLikDHEJ gIXFRJ4GuteQrkVqhjBRy4Wqp3sfwzDir93Z5TGEJVXKshGMUtw0AUuSbzjH0uRb7l3anOvkQgf Navwro4n0itkVNLZS0KbRhuokhBbJGmydN5tFGoeMTp5jov+no5yg+CBzPa2QWb7Yza78SDxNa2 VGZ+r8QsftY5p9gDYxUhY5o6jX1P+WCH5RkKdTEtWPg3CTmscurag+kA5FJq4EwjDkdF5sy3/XK 0krCzdYTDX04ROUyZQ7I0bz7Rr9HiZ4RZ6XFKqMv1vZ+y8MBqhIYJn7MhY5wPAx7kHwfLy4nu46 JiDF//JQBY= X-Received: by 2002:a17:90b:1dcc:b0:38e:6d4c:14e6 with SMTP id 98e67ed59e1d1-3933b77c874mr13623090a91.3.1786771203820; Fri, 14 Aug 2026 22:20:03 -0700 (PDT) Received: from localhost.localdomain ([49.79.111.198]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-394ea96c7fcsm5269702a91.3.2026.08.14.22.19.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Aug 2026 22:20:03 -0700 (PDT) From: Vernon Yang To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org Cc: nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, zokeefe@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vernon Yang , stable@vger.kernel.org Subject: [PATCH v2 1/3] mm: khugepaged: fix swap entry value to folio_pfn() Date: Sat, 15 Aug 2026 13:19:22 +0800 Message-ID: <20260815051924.194810-2-vernon2gm@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260815051924.194810-1-vernon2gm@gmail.com> References: <20260815051924.194810-1-vernon2gm@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Vernon Yang When the swap entries found exceed max_ptes_swap, the loop is left via break with folio still holding the xarray value that encodes the swap entry, not valid folio pointer. That value is passed to trace_mm_khugepaged_scan_file(), which feeds it to folio_pfn(). On FLATMEM and SPARSEMEM_VMEMMAP, the page_to_pfn() is plain pointer arithmetic, so the trace event merely prints bogus scan_pfn. On classic SPARSEMEM, the page_to_pfn() reads page->flags, dereferencing the tiny encoded integer and oopsing khugepaged whenever the trace event is enabled. So when folio is the swap entry value, simply set pfn to -1, just like exhausted scan naturally. And the folio_put() has maybe dropped the last reference of folio. The trace_mm_khugepaged_scan_file() is left with a dangling folio pointer. so using the folio_pfn() before dropping the reference, closing use-after-free window. Fixes: d41fd2016ed0 ("mm/khugepaged: add tracepoint to hpage_collapse_scan_file()") Cc: stable@vger.kernel.org Signed-off-by: Vernon Yang --- include/trace/events/huge_memory.h | 6 +++--- mm/khugepaged.c | 14 +++++++++----- 2 files changed, 12 insertions(+), 8 deletions(-) diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index 291fae364c62..d3572d4ef453 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -178,10 +178,10 @@ TRACE_EVENT(mm_collapse_huge_page_swapin, TRACE_EVENT(mm_khugepaged_scan_file, - TP_PROTO(struct mm_struct *mm, struct folio *folio, struct file *file, + TP_PROTO(struct mm_struct *mm, unsigned long pfn, struct file *file, int present, int swap, int result), - TP_ARGS(mm, folio, file, present, swap, result), + TP_ARGS(mm, pfn, file, present, swap, result), TP_STRUCT__entry( __field(struct mm_struct *, mm) @@ -194,7 +194,7 @@ TRACE_EVENT(mm_khugepaged_scan_file, TP_fast_assign( __entry->mm = mm; - __entry->pfn = folio ? folio_pfn(folio) : -1; + __entry->pfn = pfn; __assign_str(filename); __entry->present = present; __entry->swap = swap; diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 617bca76db49..e7830761d3a2 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2683,6 +2683,7 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, int present, swap; int node = NUMA_NO_NODE; enum scan_result result = SCAN_SUCCEED; + unsigned long pfn; present = 0; swap = 0; @@ -2720,27 +2721,23 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, * PMD-sized THP implies that we can only try * retracting the PTE table. */ - folio_put(folio); break; } node = folio_nid(folio); if (collapse_scan_abort(node, cc)) { result = SCAN_SCAN_ABORT; - folio_put(folio); break; } cc->node_load[node]++; if (!folio_test_lru(folio)) { result = SCAN_PAGE_LRU; - folio_put(folio); break; } if (folio_expected_ref_count(folio) + 1 != folio_ref_count(folio)) { result = SCAN_PAGE_COUNT; - folio_put(folio); break; } @@ -2759,7 +2756,14 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, cond_resched_rcu(); } } + if (!folio || xa_is_value(folio)) { + pfn = -1; + } else { + pfn = folio_pfn(folio); + folio_put(folio); + } rcu_read_unlock(); + if (result == SCAN_PTE_MAPPED_HUGEPAGE) cc->progress++; else @@ -2774,7 +2778,7 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, } } - trace_mm_khugepaged_scan_file(mm, folio, file, present, swap, result); + trace_mm_khugepaged_scan_file(mm, pfn, file, present, swap, result); return result; } -- 2.53.0