From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 C5A4046DFFF; Tue, 21 Jul 2026 16:23:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784651036; cv=none; b=iWRuy1A6EndEVBnSFKj4XIW9dK3+DaYublNjLciul34USN86UEFU0jDqxGps1Et4ZPl9cpMOT7/EJ44PqTnZu4gxCN5QwAZPDuNHUgCz+5MSNOtqR6AmSt0VNAW0O/XW/lYzLpNmEpp2CIggphq+d1vimNW/vCzF9/H1VBSsq0Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784651036; c=relaxed/simple; bh=n3kaZXZwqISwtbveA0LNemhUBqquwWMLzfpkLM1JX3M=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=MMVkJT2H00wuc2pFksEMwXZxgzCbnfGFfPxnybuTLueZ+gyHeKgrUCH7fVgNx/P6nPhKr5MditJHBPrIIAwu7dfEPXFEgbRfWumkwwHVcQMuZZ4jbDkO3Gx+WVOipvaRuPvPs0mWjvicmJhMElS7mfuYb1KJLwBJlVBE+/xIjks= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Hhew6m2T; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Hhew6m2T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E305A1F00A3D; Tue, 21 Jul 2026 16:23:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784651035; bh=ztzLHFgZF1pj4LHMu3VvIZzUHzFoGqe9tmkrlg/P0Q4=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=Hhew6m2TOv9DRY3CJ5gbegcSEoCRoBYhTbf45iQdRbrMKFcSNrw9pfJTGRkHal5DG pqwwjVVXbCK/99gt0PM3LFTF44MIq8GFR1Ln36lj/2CLq4/MQi2K/EbV75ihicS6s/ KZX9AWzzwaf86AoOavdoSUccw18O810scPylB6O2yn2ye8JoGgcA5FlxhKbcuTe+3g 0pt009M4LWj4WIRRFBSNZO1cvdBvD/JHkGsywJiS3euU2gHN7KcWgAo+3wnO1a4lJU kOE2hML+o2O5/WqOcYTGrDHVckMtRkBrIsMPIXn7dZVSzhO0n3VARhQSPwyFXlBaxH nLyf675udKYow== From: "Mike Rapoport (Microsoft)" Date: Tue, 21 Jul 2026 19:23:25 +0300 Subject: [PATCH RFC 02/18] x86/mm/pat: fix effective RW computation in lookup_address_in_pgd_attr() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260721-generic-set-memory-v0-1-v1-2-2c1fc62306b3@kernel.org> References: <20260721-generic-set-memory-v0-1-v1-0-2c1fc62306b3@kernel.org> In-Reply-To: <20260721-generic-set-memory-v0-1-v1-0-2c1fc62306b3@kernel.org> To: linux-mm@kvack.org Cc: Albert Ou , Andrew Morton , Andy Lutomirski , Borislav Petkov , Brendan Jackman , Catalin Marinas , Dave Hansen , David Hildenbrand , Huacai Chen , Ingo Molnar , Ingo Molnar , Kevin Brodsky , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , "H. Peter Anvin" , Suren Baghdasaryan , Thomas Gleixner , Vlastimil Babka , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, loongarch@lists.linux.dev, x86@kernel.org, Juergen Gross X-Mailer: b4 0.16-dev lookup_address_in_pgd_attr() accumulates the effective NX and RW bits of the walked page table levels so that verify_rwx() can detect mappings that are both writable and executable. The RW bits are folded into a bool with rw &= pXd_flags(*pXd) & _PAGE_RW; but _PAGE_RW is 0x2. So consider the accumulation line: rw &= pXd_flags(*pXd) & _PAGE_RW; where rw=0x1 and the right side evaluates down to 0x2. It'll end up doing: rw = 0x1 & 0x2 and rw always ends up 0. This way rw becomes false at the first level walked, regardless of the actual permissions, and verify_rwx() treats every mapping as non-writable and never reports a W^X violation. Add double negation to the right side to normalize the _PAGE_RW flag to 0 or 1. Fixes: ceb647b4b529 ("x86/pat: Introduce lookup_address_in_pgd_attr()") Assisted-by: Copilot:claude-opus-4.8 Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Juergen Gross --- arch/x86/mm/pat/set_memory.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index e8316f5ffa8a..9382f1d6194f 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -730,7 +730,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, *level = PG_LEVEL_512G; *nx |= pgd_flags(*pgd) & _PAGE_NX; - *rw &= pgd_flags(*pgd) & _PAGE_RW; + *rw &= !!(pgd_flags(*pgd) & _PAGE_RW); p4d = p4d_offset(pgd, address); if (p4d_none(*p4d)) @@ -741,7 +741,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, *level = PG_LEVEL_1G; *nx |= p4d_flags(*p4d) & _PAGE_NX; - *rw &= p4d_flags(*p4d) & _PAGE_RW; + *rw &= !!(p4d_flags(*p4d) & _PAGE_RW); pud = pud_offset(p4d, address); if (pud_none(*pud)) @@ -752,7 +752,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, *level = PG_LEVEL_2M; *nx |= pud_flags(*pud) & _PAGE_NX; - *rw &= pud_flags(*pud) & _PAGE_RW; + *rw &= !!(pud_flags(*pud) & _PAGE_RW); pmd = pmd_offset(pud, address); if (pmd_none(*pmd)) @@ -763,7 +763,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, *level = PG_LEVEL_4K; *nx |= pmd_flags(*pmd) & _PAGE_NX; - *rw &= pmd_flags(*pmd) & _PAGE_RW; + *rw &= !!(pmd_flags(*pmd) & _PAGE_RW); return pte_offset_kernel(pmd, address); } -- 2.53.0