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[PATCH] /dev/mem: validate mmap requests

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Add a hook so architectures can validate /dev/mem mmap requests.

This is analogous to validation we already perform in the read/write
paths.

The identity mapping scheme used on ia64 requires that each 16MB or
64MB granule be accessed with exactly one attribute (write-back or
uncacheable).  This avoids "attribute aliasing", which can cause a
machine check.

Sample problem scenario:
  - Machine supports VGA, so it has uncacheable (UC) MMIO at 640K-768K
  - efi_memmap_init() discards any write-back (WB) memory in the first granule
  - Application (e.g., "hwinfo") mmaps /dev/mem, offset 0
  - hwinfo receives UC mapping (the default, since memmap says "no WB here")
  - Machine check abort (on chipsets that don't support UC access to WB
    memory, e.g., sx1000)

In the scenario above, the only choices are
  - Use WB for hwinfo mmap.  Can't do this because it causes attribute
    aliasing with the UC mapping for the VGA MMIO space.
  - Use UC for hwinfo mmap.  Can't do this because the chipset may not
    support UC for that region.
  - Disallow the hwinfo mmap with -EINVAL.  That's what this patch does.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Bjorn Helgaas 2006-01-08 01:04:13 -08:00 committed by Linus Torvalds
parent 44ac841390
commit 80851ef2a5
3 changed files with 133 additions and 60 deletions
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178
arch/ia64/kernel/efi.c
View File

@ -247,6 +247,32 @@ typedef struct kern_memdesc {
static kern_memdesc_t *kern_memmap;
#define efi_md_size(md) (md->num_pages << EFI_PAGE_SHIFT)
static inline u64
kmd_end(kern_memdesc_t *kmd)
{
return (kmd->start + (kmd->num_pages << EFI_PAGE_SHIFT));
}
static inline u64
efi_md_end(efi_memory_desc_t *md)
{
return (md->phys_addr + efi_md_size(md));
}
static inline int
efi_wb(efi_memory_desc_t *md)
{
return (md->attribute & EFI_MEMORY_WB);
}
static inline int
efi_uc(efi_memory_desc_t *md)
{
return (md->attribute & EFI_MEMORY_UC);
}
static void
walk (efi_freemem_callback_t callback, void *arg, u64 attr)
{
@ -595,8 +621,8 @@ efi_get_iobase (void)
return 0;
}
u32
efi_mem_type (unsigned long phys_addr)
static efi_memory_desc_t *
efi_memory_descriptor (unsigned long phys_addr)
{
void *efi_map_start, *efi_map_end, *p;
efi_memory_desc_t *md;
@ -610,55 +636,117 @@ efi_mem_type (unsigned long phys_addr)
md = p;
if (phys_addr - md->phys_addr < (md->num_pages << EFI_PAGE_SHIFT))
return md->type;
return md;
}
return 0;
}
static int
efi_memmap_has_mmio (void)
{
void *efi_map_start, *efi_map_end, *p;
efi_memory_desc_t *md;
u64 efi_desc_size;
efi_map_start = __va(ia64_boot_param->efi_memmap);
efi_map_end = efi_map_start + ia64_boot_param->efi_memmap_size;
efi_desc_size = ia64_boot_param->efi_memdesc_size;
for (p = efi_map_start; p < efi_map_end; p += efi_desc_size) {
md = p;
if (md->type == EFI_MEMORY_MAPPED_IO)
return 1;
}
return 0;
}
u32
efi_mem_type (unsigned long phys_addr)
{
efi_memory_desc_t *md = efi_memory_descriptor(phys_addr);
if (md)
return md->type;
return 0;
}
u64
efi_mem_attributes (unsigned long phys_addr)
{
void *efi_map_start, *efi_map_end, *p;
efi_memory_desc_t *md;
u64 efi_desc_size;
efi_memory_desc_t *md = efi_memory_descriptor(phys_addr);
efi_map_start = __va(ia64_boot_param->efi_memmap);
efi_map_end = efi_map_start + ia64_boot_param->efi_memmap_size;
efi_desc_size = ia64_boot_param->efi_memdesc_size;
for (p = efi_map_start; p < efi_map_end; p += efi_desc_size) {
md = p;
if (phys_addr - md->phys_addr < (md->num_pages << EFI_PAGE_SHIFT))
return md->attribute;
}
if (md)
return md->attribute;
return 0;
}
EXPORT_SYMBOL(efi_mem_attributes);
/*
* Determines whether the memory at phys_addr supports the desired
* attribute (WB, UC, etc). If this returns 1, the caller can safely
* access *size bytes at phys_addr with the specified attribute.
*/
static int
efi_mem_attribute_range (unsigned long phys_addr, unsigned long *size, u64 attr)
{
efi_memory_desc_t *md = efi_memory_descriptor(phys_addr);
unsigned long md_end;
if (!md || (md->attribute & attr) != attr)
return 0;
do {
md_end = efi_md_end(md);
if (phys_addr + *size <= md_end)
return 1;
md = efi_memory_descriptor(md_end);
if (!md || (md->attribute & attr) != attr) {
*size = md_end - phys_addr;
return 1;
}
} while (md);
return 0;
}
/*
* For /dev/mem, we only allow read & write system calls to access
* write-back memory, because read & write don't allow the user to
* control access size.
*/
int
valid_phys_addr_range (unsigned long phys_addr, unsigned long *size)
{
void *efi_map_start, *efi_map_end, *p;
efi_memory_desc_t *md;
u64 efi_desc_size;
return efi_mem_attribute_range(phys_addr, size, EFI_MEMORY_WB);
}
efi_map_start = __va(ia64_boot_param->efi_memmap);
efi_map_end = efi_map_start + ia64_boot_param->efi_memmap_size;
efi_desc_size = ia64_boot_param->efi_memdesc_size;
/*
* We allow mmap of anything in the EFI memory map that supports
* either write-back or uncacheable access. For uncacheable regions,
* the supported access sizes are system-dependent, and the user is
* responsible for using the correct size.
*
* Note that this doesn't currently allow access to hot-added memory,
* because that doesn't appear in the boot-time EFI memory map.
*/
int
valid_mmap_phys_addr_range (unsigned long phys_addr, unsigned long *size)
{
if (efi_mem_attribute_range(phys_addr, size, EFI_MEMORY_WB))
return 1;
for (p = efi_map_start; p < efi_map_end; p += efi_desc_size) {
md = p;
if (efi_mem_attribute_range(phys_addr, size, EFI_MEMORY_UC))
return 1;
if (phys_addr - md->phys_addr < (md->num_pages << EFI_PAGE_SHIFT)) {
if (!(md->attribute & EFI_MEMORY_WB))
return 0;
/*
* Some firmware doesn't report MMIO regions in the EFI memory map.
* The Intel BigSur (a.k.a. HP i2000) has this problem. In this
* case, we can't use the EFI memory map to validate mmap requests.
*/
if (!efi_memmap_has_mmio())
return 1;
if (*size > md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT) - phys_addr)
*size = md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT) - phys_addr;
return 1;
}
}
return 0;
}
@ -707,32 +795,6 @@ efi_uart_console_only(void)
return 0;
}
#define efi_md_size(md) (md->num_pages << EFI_PAGE_SHIFT)
static inline u64
kmd_end(kern_memdesc_t *kmd)
{
return (kmd->start + (kmd->num_pages << EFI_PAGE_SHIFT));
}
static inline u64
efi_md_end(efi_memory_desc_t *md)
{
return (md->phys_addr + efi_md_size(md));
}
static inline int
efi_wb(efi_memory_desc_t *md)
{
return (md->attribute & EFI_MEMORY_WB);
}
static inline int
efi_uc(efi_memory_desc_t *md)
{
return (md->attribute & EFI_MEMORY_UC);
}
/*
* Look for the first granule aligned memory descriptor memory
* that is big enough to hold EFI memory map. Make sure this

14
drivers/char/mem.c
View File

@ -101,6 +101,11 @@ static inline int valid_phys_addr_range(unsigned long addr, size_t *count)
return 1;
}
static inline int valid_mmap_phys_addr_range(unsigned long addr, size_t *size)
{
return 1;
}
#endif
/*
@ -244,15 +249,20 @@ static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
static int mmap_mem(struct file * file, struct vm_area_struct * vma)
{
size_t size = vma->vm_end - vma->vm_start;
if (!valid_mmap_phys_addr_range(vma->vm_pgoff << PAGE_SHIFT, &size))
return -EINVAL;
vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
vma->vm_end - vma->vm_start,
size,
vma->vm_page_prot);
/* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
if (remap_pfn_range(vma,
vma->vm_start,
vma->vm_pgoff,
vma->vm_end-vma->vm_start,
size,
vma->vm_page_prot))
return -EAGAIN;
return 0;

1
include/asm-ia64/io.h
View File

@ -89,6 +89,7 @@ phys_to_virt (unsigned long address)
#define ARCH_HAS_VALID_PHYS_ADDR_RANGE
extern int valid_phys_addr_range (unsigned long addr, size_t *count); /* efi.c */
extern int valid_mmap_phys_addr_range (unsigned long addr, size_t *count);
/*
* The following two macros are deprecated and scheduled for removal.