linux-kernel - [PATCH 2/3] x86/devmem: remove phys_mem_access_prot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250520152030.1499670-2-arnd@kernel.org>
Date: Tue, 20 May 2025 17:20:29 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Dave Hansen <dave.hansen@...ux.intel.com>,
	Dan Williams <dan.j.williams@...el.com>
Cc: Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	x86@...nel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nikolay Borisov <nik.borisov@...e.com>,
	linux-kernel@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 2/3] x86/devmem: remove phys_mem_access_prot_allowed()

From: Arnd Bergmann <arnd@...db.de>

phys_mem_access_prot_allowed() was originally a workaround for
certain 32-bit CPUs, but after commit 1886297ce0c8 ("x86/mm/pat:
Fix BUG_ON() in mmap_mem() on QEMU/i386"), it no longer does anything
special as the only remaining bit now is the same logic that follows in
phys_mem_access_prot(), mapping everything as normal memory except when
either O_DSYNC is set or the address is highmem.

Just remove the thing entirely.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/mm/pat/memtype.c | 15 ---------------
 drivers/char/mem.c        | 10 ----------
 include/linux/pgtable.h   |  2 --
 3 files changed, 27 deletions(-)

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index fe24b8d2dc4b..fec14f1f53a6 100644
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -781,21 +781,6 @@ static inline void pgprot_set_cachemode(pgprot_t *prot, enum page_cache_mode pcm
 			 cachemode2protval(pcm));
 }
 
-int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
-				unsigned long size, pgprot_t *vma_prot)
-{
-	enum page_cache_mode pcm = _PAGE_CACHE_MODE_WB;
-
-	if (!pat_enabled())
-		return 1;
-
-	if (file->f_flags & O_DSYNC)
-		pcm = _PAGE_CACHE_MODE_UC_MINUS;
-
-	pgprot_set_cachemode(vma_prot, pcm);
-	return 1;
-}
-
 /*
  * Change the memory type for the physical address range in kernel identity
  * mapping space if that range is a part of identity map.
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 85f963ce3b2d..30a5c0e0542a 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -256,12 +256,6 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
 	return written;
 }
 
-int __weak phys_mem_access_prot_allowed(struct file *file,
-	unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
-{
-	return 1;
-}
-
 #ifndef __HAVE_PHYS_MEM_ACCESS_PROT
 
 /*
@@ -387,10 +381,6 @@ static int mmap_mem(struct file *file, struct vm_area_struct *vma)
 	if (!range_is_allowed(vma->vm_pgoff, size))
 		return -EPERM;
 
-	if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
-						&vma->vm_page_prot))
-		return -EINVAL;
-
 	vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 						 size,
 						 vma->vm_page_prot);
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index adbebe2c6ce4..15b5a6b0943f 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1764,8 +1764,6 @@ static inline int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
 #endif
 
 struct file;
-int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
-			unsigned long size, pgprot_t *vma_prot);
 
 #ifndef CONFIG_X86_ESPFIX64
 static inline void init_espfix_bsp(void) { }
-- 
2.39.5