linux-kernel - [tip:x86/urgent] x86/mm: Prevent bogus warnings with "noexec=off"

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Message-ID: <tip-510bb96fe5b3480b4b22d815786377e54cb701e7@git.kernel.org>
Date:   Tue, 16 Apr 2019 00:46:06 -0700
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     xose.vazquez@...il.com, riel@...riel.com, tglx@...utronix.de,
        hpa@...or.com, mingo@...nel.org, luto@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: [tip:x86/urgent] x86/mm: Prevent bogus warnings with "noexec=off"

Commit-ID:  510bb96fe5b3480b4b22d815786377e54cb701e7
Gitweb:     https://git.kernel.org/tip/510bb96fe5b3480b4b22d815786377e54cb701e7
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 15 Apr 2019 10:46:07 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 16 Apr 2019 09:42:10 +0200

x86/mm: Prevent bogus warnings with "noexec=off"

Xose Vazquez Perez reported boot warnings when NX is disabled on the kernel command line.

__early_set_fixmap() triggers this warning:

  attempted to set unsupported pgprot:    8000000000000163
			       bits:      8000000000000000
			       supported: 7fffffffffffffff

  WARNING: CPU: 0 PID: 0 at arch/x86/include/asm/pgtable.h:537
			    __early_set_fixmap+0xa2/0xff

because it uses __default_kernel_pte_mask to mask out unsupported bits.

Use __supported_pte_mask instead.

Disabling NX on the command line also triggers the NX warning in the page
table mapping check:

  WARNING: CPU: 1 PID: 1 at arch/x86/mm/dump_pagetables.c:262 note_page+0x2ae/0x650
  ....

Make the warning depend on NX set in __supported_pte_mask.

Reported-by: Xose Vazquez Perez <xose.vazquez@...il.com>
Tested-by: Xose Vazquez Perez <xose.vazquez@...il.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...riel.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1904151037530.1729@nanos.tec.linutronix.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/mm/dump_pagetables.c | 3 ++-
 arch/x86/mm/ioremap.c         | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index ee8f8ab46941..c0309ea9abee 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -259,7 +259,8 @@ static void note_wx(struct pg_state *st)
 #endif
 	/* Account the WX pages */
 	st->wx_pages += npages;
-	WARN_ONCE(1, "x86/mm: Found insecure W+X mapping at address %pS\n",
+	WARN_ONCE(__supported_pte_mask & _PAGE_NX,
+		  "x86/mm: Found insecure W+X mapping at address %pS\n",
 		  (void *)st->start_address);
 }
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 0029604af8a4..dd73d5d74393 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -825,7 +825,7 @@ void __init __early_set_fixmap(enum fixed_addresses idx,
 	pte = early_ioremap_pte(addr);
 
 	/* Sanitize 'prot' against any unsupported bits: */
-	pgprot_val(flags) &= __default_kernel_pte_mask;
+	pgprot_val(flags) &= __supported_pte_mask;
 
 	if (pgprot_val(flags))
 		set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));