From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D6F3E18DB17; Wed, 23 Apr 2025 14:55:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745420123; cv=none; b=JE0diAD3Zm05EsBtZigWnzrVOhLmTXpfe8AUmToJBcEBJg1XEyLRnWtc3UtDezcOw9aC5P/yMdFxyBkTPe3dkr6sLyL2HLBssTJJhwlPvIegmlkSum9o5BbplIKoBG4b+xsVRFa3nL1GEgeLqNgO+YeAS1u432HCpBQhCAlIIhU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745420123; c=relaxed/simple; bh=mPe1EJBcWzcp15OSicOrLMvdgJVQhsBf7QcLik08mzM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LKffdsvtd9wOLaGb1J0GppRXWk9VwJGyzWJenLjUhJs2k5qshUaERDbqP4kOXQrKK9VcbZFrYyxmnMgt1eJHvaD640PRumvsT2p52GJtHkhyzMpKcCKC2lBThkjp8MrBbwIoTP3Jzho7C+Hn8Pn5R4qwYX+mT+uVJw6N/R0SzHA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xRBXwfKQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xRBXwfKQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A951C4CEE2; Wed, 23 Apr 2025 14:55:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1745420123; bh=mPe1EJBcWzcp15OSicOrLMvdgJVQhsBf7QcLik08mzM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xRBXwfKQhnq/xUvwa9uOMnKIUkDHfuoeSr+29j53uqYEk9l72Qa5BhrcHfwrW4UlA Q1dg/0Tfcu15cyx+XMTVP2CHcOkf87qIxGjjpsT8oenoXydfLWcsU7o77trbZ1OuTE NeuT2VUpYsRaPohAbqTxo0PqncmIN5geeNX3eDKE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, kernel test robot , "Matthew Wilcox (Oracle)" , Ingo Molnar , Linus Torvalds , Sasha Levin Subject: [PATCH 6.6 040/393] x86/mm: Clear _PAGE_DIRTY for kernel mappings when we clear _PAGE_RW Date: Wed, 23 Apr 2025 16:38:56 +0200 Message-ID: <20250423142644.949341713@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250423142643.246005366@linuxfoundation.org> References: <20250423142643.246005366@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Matthew Wilcox (Oracle) [ Upstream commit c1fcf41cf37f7a3fd3bbf6f0c04aba3ea4258888 ] The bit pattern of _PAGE_DIRTY set and _PAGE_RW clear is used to mark shadow stacks. This is currently checked for in mk_pte() but not pfn_pte(). If we add the check to pfn_pte(), it catches vfree() calling set_direct_map_invalid_noflush() which calls __change_page_attr() which loads the old protection bits from the PTE, clears the specified bits and uses pfn_pte() to construct the new PTE. We should, therefore, for kernel mappings, clear the _PAGE_DIRTY bit consistently whenever we clear _PAGE_RW. I opted to do it in the callers in case we want to use __change_page_attr() to create shadow stacks inside the kernel at some point in the future. Arguably, we might also want to clear _PAGE_ACCESSED here. Note that the 3 functions involved: __set_pages_np() kernel_map_pages_in_pgd() kernel_unmap_pages_in_pgd() Only ever manipulate non-swappable kernel mappings, so maintaining the DIRTY:1|RW:0 special pattern for shadow stacks and DIRTY:0 pattern for non-shadow-stack entries can be maintained consistently and doesn't result in the unintended clearing of a live dirty bit that could corrupt (destroy) dirty bit information for user mappings. Reported-by: kernel test robot Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Ingo Molnar Acked-by: Linus Torvalds Link: https://lore.kernel.org/r/174051422675.10177.13226545170101706336.tip-bot2@tip-bot2 Closes: https://lore.kernel.org/oe-lkp/202502241646.719f4651-lkp@intel.com Signed-off-by: Sasha Levin --- arch/x86/mm/pat/set_memory.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 2d850f6bae701..525794f1eefb3 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -2374,7 +2374,7 @@ static int __set_pages_np(struct page *page, int numpages) .pgd = NULL, .numpages = numpages, .mask_set = __pgprot(0), - .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW), + .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY), .flags = CPA_NO_CHECK_ALIAS }; /* @@ -2453,7 +2453,7 @@ int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address, .pgd = pgd, .numpages = numpages, .mask_set = __pgprot(0), - .mask_clr = __pgprot(~page_flags & (_PAGE_NX|_PAGE_RW)), + .mask_clr = __pgprot(~page_flags & (_PAGE_NX|_PAGE_RW|_PAGE_DIRTY)), .flags = CPA_NO_CHECK_ALIAS, }; @@ -2496,7 +2496,7 @@ int __init kernel_unmap_pages_in_pgd(pgd_t *pgd, unsigned long address, .pgd = pgd, .numpages = numpages, .mask_set = __pgprot(0), - .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW), + .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY), .flags = CPA_NO_CHECK_ALIAS, }; -- 2.39.5