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=1793834083; b=tav1ExIACHxKJLnVDPlIHDhPOQtHijlshrlPdUS/lOiuMUqe9T6w2qoAonrKSd00SG81 xg+lM4Cisz1c20paQqzOI6JAIn01LjgSResOtestHKS+pLXYQREmtQTBpwr1yr2nE8rAO S3r5GktHFGp/8NCDZD5MbNrkw7VVIVRJmU1U/LcBbdo4jdV/ZNGpG9Ffg0HS6MzjVk98h QgjxABUoYlsecIaC3qbmx6CAUf0OZzbiK9Gbpxlej82bvL1gehPu8SYaxJNloX2dlUI/s MOWF5TfufUMkY101IrTrj2UyEwQb9d3X6JD3eIYuTXdxC7XkMNIOwBdt7Ie5KQXup2g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793834083; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=+mPBoAFZaI/kXrME1blIrD7m0pkImBMDcD7wGGRHj9M=; b=U5Xm1mLq+SHyb7T7kUcsKzGO3mo+f60m6RBrLiNTn/O9MXq/zldBA1Bs0IgJl865GP67 5+Ou5i7Fcl+CsfouQjSIKT4jpJ4fkR4iK0Z29QyQhzOTADl3LZAlWyIdXA1S/oRW1VZLa 5qWcl9tIeFPQyhIEhpD1yY2uknC0bVqJ4TdKdljiT7vzZX2dQw8cNqXhu9qFiPVRpkr7w c+CHJVOdJWcP2WecEQ5iAUx3TMcY2WOKR5Gme5O2PYPfHZv8JGpLxoQ+b9RbqQUWEXIRn c4WQdE7ZjOYbxgVdS3588PvGRh/Wi7XkDyAqbn5+X72NueP5WhPW4I9AHL3uo6m4Naw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=LjdSz0Ud; 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 A5500606A31B for ; Wed, 4 Nov 2026 23:14:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=LjdSz0Ud Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A96D1F0093A; Wed, 4 Nov 2026 23:14:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793834082; bh=+mPBoAFZaI/kXrME1blIrD7m0pkImBMDcD7wGGRHj9M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LjdSz0UdPEma2jkh9nEG82urMHFp+Ybiyd/j9O2d1L3ogDGqrRtWMInGdf5hFVF5H FSDJEXB9vyNN4bClUHt7WXfxRb05t6WJJenunuM/wJS5/A9Ms7KB9+Ap/RAq9JF3sJ Uj+dbdI6pnOCu0Y1VHkkjpJerSO4IUu+9eOrfy2vWQB5ASPfjsRITk28gAvKzei/mb 55IHxnHHMMJGf0+jQ+TdTdDa3u9E3gAz/u1Jmh+UdJPeCWqaAgKATOAl3yAvlR5QK7 0VZr0HjxkUvJXctksqUmZWe/GRZtXUYunbClaFzg7w/RC5NkeBmrX4Qj9HTqVCViZj UgmiRz2dOsBYg== From: Sasha Levin To: stable@vger.kernel.org Cc: Vernon Yang , Andrew Morton , "David Hildenbrand (Arm)" , "Lorenzo Stoakes (ARM)" , Barry Song , Dev Jain , Lance Yang , Ryan Roberts , Zach O'Keefe , Sasha Levin Subject: [PATCH 6.6.y] mm: khugepaged: fix folio is used after folio_put/unlock() Date: Wed, 4 Nov 2026 18:14:40 -0500 Message-ID: <20261104231424.891478-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110413-cacti-bonded-6534@gregkh> References: <2026110413-cacti-bonded-6534@gregkh> 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 From: Vernon Yang [ Upstream commit 9010383e71e6ce75fcd3c8f87133c8ce6c0e6ab4 ] 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: [ sashal: adjusted collapse_file() declaration context to preserve struct page *tmp instead of struct folio *tmp ] Signed-off-by: Sasha Levin --- include/trace/events/huge_memory.h | 6 +++--- mm/khugepaged.c | 4 +++- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index 37f2443b3cdb0..a1ac19bab4a2d 100644 --- 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; diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 42330aeb76386..1f7c0655d8db9 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1788,6 +1788,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, struct page *page; struct page *tmp, *dst; struct folio *folio, *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); @@ -1800,6 +1801,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, 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); @@ -2207,7 +2209,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, 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; } -- 2.53.0