From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794061574; b=KU8lYFp4RnRqq0lx0bUvsG+A038k/i2ozWzfricJ+6RmbCRsgDVcvACZVXZm3/ra1dSY VpKQnpKVuS4KqDVDOn6wkHbq4RK9OT8s2+wttXZHfKDNxaPtlRwoFxJKIpe8n+4tXdy6z vVrTRlO0tveSF9MvgWZXViF8akbAQ7zWp8df7QmxtfjWzrkmg2zMz2bb+Wb0uOKsWbZ0i 1gWytKHMZTZ7ApGZriGxssTDFdVMW9dPhvLreFWsk/Pe2ZWBcii1Sy0UZiUorsCnANCFa RP7ATlyiVkue+Z1WkXwI4NGJQO65O8EkaXqMM0NvnCQFAbFhKM8a4d3vt2fSOOMhMdg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794061574; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=G0EZudA3RjnRfBjs6AF4hK1IfOorzyX244Gws7hW5rY=; b=Q1Nig5QD3RSfHFDqtDeS15sgz3XgHoBdRbIQaclP1at0wrxgkGAfCxVVAKXcK/RcqNZO Vx9pMZeCxvcicvhQ0wEPkKDDrQ2VdM1KZv60csQTeBsqab5F8/EBP9JV7UuZSCCXdceiA bUEes0arEGTjQaI5I0nTQPk5OeIZoduCJi6ZJaH5zSB3aouxLRE7C7p7lsV8xA0Uxafut P1A5LktDII+El7MsTjiPY2pI5k6+/PLPpbe1L7MZk0ngtN6GfyaRHAKxWsheQvogtOVMl 9Kk6NoJ5/PlAOVJqev7PN4cQ5BvGDh3lNmjlZBIah/YsDA+LtC9FiS96ho+Ng28KAfw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qDcnm8b8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A265606A32D; Sat, 7 Nov 2026 14:26:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qDcnm8b8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC4361F0089F; Sat, 7 Nov 2026 14:26:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794061574; bh=G0EZudA3RjnRfBjs6AF4hK1IfOorzyX244Gws7hW5rY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qDcnm8b8Rpr9lCg0zodtDV7arIIdcZJlUNl+g3Vzf5X0oON2Jmsri6LqjTFMu/VLZ o2DmExVyjCgVvYsSPBnYz2G+iEuDz5q+2ENs1u+kRgmlF2e6Kopwb+lZSg1IXl/tnE ZEeDESz15s7yj5jtfICdQrtep3tWM3GivV+LLyUA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vernon Yang , Andrew Morton , "David Hildenbrand (Arm)" , "Lorenzo Stoakes (ARM)" , Barry Song , Dev Jain , Lance Yang , Ryan Roberts , Zach OKeefe Subject: [PATCH 6.12 0651/1536] mm: khugepaged: fix folio is used after folio_put/unlock() Date: Sat, 7 Nov 2026 08:44:27 -0500 Message-ID: <20261107135015.812602408@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134957.653319350@linuxfoundation.org> References: <20261107134957.653319350@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vernon Yang commit 9010383e71e6ce75fcd3c8f87133c8ce6c0e6ab4 upstream. On the rollback path, folio_put() has already dropped the last reference of new_folio. On the success path, new_folio is already unlocked and can be freed concurrently. The trace_mm_khugepaged_collapse_file() is left with a dangling folio pointer. So using the folio_pfn() before dropping the reference, closing use-after-free window. Link: https://lore.kernel.org/20260909025804.3233645-4-vernon2gm@gmail.com Fixes: 4c9473e87e75 ("mm/khugepaged: add tracepoint to collapse_file()") Signed-off-by: Vernon Yang Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Acked-by: Lorenzo Stoakes (ARM) Cc: Barry Song Cc: Dev Jain Cc: Lance Yang Cc: Ryan Roberts Cc: Zach O'Keefe Cc: Signed-off-by: Greg Kroah-Hartman --- include/trace/events/huge_memory.h | 6 +++--- mm/khugepaged.c | 4 +++- 2 files changed, 6 insertions(+), 4 deletions(-) --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -207,10 +207,10 @@ TRACE_EVENT(mm_khugepaged_scan_file, ); TRACE_EVENT(mm_khugepaged_collapse_file, - TP_PROTO(struct mm_struct *mm, struct folio *new_folio, pgoff_t index, + TP_PROTO(struct mm_struct *mm, unsigned long new_pfn, pgoff_t index, unsigned long addr, bool is_shmem, struct file *file, int nr, int result), - TP_ARGS(mm, new_folio, index, addr, is_shmem, file, nr, result), + TP_ARGS(mm, new_pfn, index, addr, is_shmem, file, nr, result), TP_STRUCT__entry( __field(struct mm_struct *, mm) __field(unsigned long, hpfn) @@ -224,7 +224,7 @@ TRACE_EVENT(mm_khugepaged_collapse_file, TP_fast_assign( __entry->mm = mm; - __entry->hpfn = new_folio ? folio_pfn(new_folio) : -1; + __entry->hpfn = new_pfn; __entry->index = index; __entry->addr = addr; __entry->is_shmem = is_shmem; --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1811,6 +1811,7 @@ static int collapse_file(struct mm_struc struct address_space *mapping = file->f_mapping; struct page *dst; struct folio *folio, *tmp, *new_folio; + unsigned long new_pfn = -1; pgoff_t index = 0, end = start + HPAGE_PMD_NR; LIST_HEAD(pagelist); XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); @@ -1823,6 +1824,7 @@ static int collapse_file(struct mm_struc result = alloc_charge_folio(&new_folio, mm, cc); if (result != SCAN_SUCCEED) goto out; + new_pfn = folio_pfn(new_folio); mapping_set_update(&xas, mapping); @@ -2242,7 +2244,7 @@ rollback: folio_put(new_folio); out: VM_BUG_ON(!list_empty(&pagelist)); - trace_mm_khugepaged_collapse_file(mm, new_folio, index, addr, is_shmem, file, HPAGE_PMD_NR, result); + trace_mm_khugepaged_collapse_file(mm, new_pfn, index, addr, is_shmem, file, HPAGE_PMD_NR, result); return result; }