From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D51F6148FE6 for ; Sat, 21 Jun 2025 05:41:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.97.179.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750484489; cv=none; b=VXdRPrwwvlKyKMLDWbJ7JvGOtt8MJVLAopxqQ5Vte/+DJEskLU1sMIFoI9hhKoEs2DbpJnQDDcnyvy6O7CuFQbUduVlowSqqfgyzcNBliTBBoYclqKMPu6GdFIPBmWwC/7muI7sP5A8vnK4tRMoTTgxvDW+WdLHxFXEkVpiD8kg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750484489; c=relaxed/simple; bh=PaCzguNuKpgpkS1Ht90EHHsGB7EyWxE8HbKsrSuTtII=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LeV4U5Dj8LBl45XoR+8q7MEX6wTfAnKNZUWvkgIGTXqkbpRlCgW/0qSzxy0LAZ1kZaYYRm4m+IZp2Xm/pXKEGmX4Xmk+9LNQPmcyZMfHzTtdey6YicRT+lrFa970zZauFqiFgpUozvfwCCTi9gZFnV75roZQE64CI7Kvq3dM04E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=Y543K1KB; arc=none smtp.client-ip=213.97.179.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="Y543K1KB" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=/wJvppgnd/Vdhxv6+T+2wl+XdmDasZO7FOmu6Jbq3CA=; b=Y543K1KB0QdsEizFowxO0MMatj mMaMJzwYMxe1dfe1/C4BtJsthn0ldQI2vNz+N3vI9GmWKsgqqZnP7BHd+D42rAjQctFQ2ibfTX3Fk zWYgl3L8fVtVRtEpPCCBQK8pSRxi0SUR1yLL1s8ARGRxTWxxIYvKw35qGKbsqbhd0TpMO2jLfS8Tk kTpaOXy85l0RkxxkEwb0sF+U6iTDBOkQHVbXAAS5bqiQvjHMn3IJUVNS2Dxr43f4UQkIztF5VU2nN pyhy1KTEFmvajYYDPKryjkggoIu1eFkebtpHvtDC6zB6Fl7ESTB0kHIUEC+oL5aSwbi9w9tStFBKl nMPFgmTg==; Received: from 114-44-248-185.dynamic-ip.hinet.net ([114.44.248.185] helo=gavin-HP-Z840-Workstation..) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1uSqyX-006HAh-D8; Sat, 21 Jun 2025 07:41:14 +0200 From: Gavin Guo To: Andrew Morton Cc: David Hildenbrand , Hugh Dickins , Zi Yan , Gavin Shan , Florent Revest , Matthew Wilcox , Miaohe Lin , stable@vger.kernel.org Subject: [PATCH 5.15.y] mm/huge_memory: fix dereferencing invalid pmd migration entry Date: Sat, 21 Jun 2025 13:41:06 +0800 Message-ID: <20250621054106.3649809-1-gavinguo@igalia.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2025051204-tidal-lake-6ae7@gregkh> References: <2025051204-tidal-lake-6ae7@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit [ Upstream commit be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7 ] When migrating a THP, concurrent access to the PMD migration entry during a deferred split scan can lead to an invalid address access, as illustrated below. To prevent this invalid access, it is necessary to check the PMD migration entry and return early. In this context, there is no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the equality of the target folio. Since the PMD migration entry is locked, it cannot be served as the target. Mailing list discussion and explanation from Hugh Dickins: "An anon_vma lookup points to a location which may contain the folio of interest, but might instead contain another folio: and weeding out those other folios is precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of replacing the wrong folio" comment a few lines above it) is for." BUG: unable to handle page fault for address: ffffea60001db008 CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60 Call Trace: try_to_migrate_one+0x28c/0x3730 rmap_walk_anon+0x4f6/0x770 unmap_folio+0x196/0x1f0 split_huge_page_to_list_to_order+0x9f6/0x1560 deferred_split_scan+0xac5/0x12a0 shrinker_debugfs_scan_write+0x376/0x470 full_proxy_write+0x15c/0x220 vfs_write+0x2fc/0xcb0 ksys_write+0x146/0x250 do_syscall_64+0x6a/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e The bug is found by syzkaller on an internal kernel, then confirmed on upstream. Link: https://lkml.kernel.org/r/20250421113536.3682201-1-gavinguo@igalia.com Link: https://lore.kernel.org/all/20250414072737.1698513-1-gavinguo@igalia.com/ Link: https://lore.kernel.org/all/20250418085802.2973519-1-gavinguo@igalia.com/ Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path") Signed-off-by: Gavin Guo Acked-by: David Hildenbrand Acked-by: Hugh Dickins Acked-by: Zi Yan Reviewed-by: Gavin Shan Cc: Florent Revest Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Signed-off-by: Andrew Morton [gavin: backport the migration checking logic to __split_huge_pmd] Signed-off-by: Gavin Guo --- mm/huge_memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9139da4baa39..e9c5de967b2c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2161,7 +2161,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, VM_BUG_ON(freeze && !page); if (page) { VM_WARN_ON_ONCE(!PageLocked(page)); - if (page != pmd_page(*pmd)) + if (is_pmd_migration_entry(*pmd) || page != pmd_page(*pmd)) goto out; } base-commit: 1c700860e8bc079c5c71d73c55e51865d273943c -- 2.43.0