diff options
| -rw-r--r-- | arch/x86/Kconfig.debug | 12 | ||||
| -rw-r--r-- | arch/x86/mm/init_32.c | 19 | ||||
| -rw-r--r-- | arch/x86/mm/init_64.c | 20 | ||||
| -rw-r--r-- | drivers/char/mem.c | 28 | ||||
| -rw-r--r-- | include/asm-x86/page.h | 1 |
5 files changed, 80 insertions, 0 deletions
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index 610aaec..0c1890c 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -5,6 +5,18 @@ config TRACE_IRQFLAGS_SUPPORT source "lib/Kconfig.debug" +config NONPROMISC_DEVMEM + bool "Disable promiscuous /dev/mem" + default y + help + The /dev/mem file by default only allows userspace access to PCI + space and the BIOS code and data regions. This is sufficient for + dosemu and X and all common users of /dev/mem. With this config + option, you allow userspace access to all of memory, including + kernel and userspace memory. Accidental access to this is + obviously disasterous, but specific access can be used by people + debugging the kernel. + config EARLY_PRINTK bool "Early printk" if EMBEDDED default y diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index 9ec62da..39852d5 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -227,6 +227,25 @@ static inline int page_kills_ppro(unsigned long pagenr) return 0; } +/* + * devmem_is_allowed() checks to see if /dev/mem access to a certain address + * is valid. The argument is a physical page number. + * + * + * On x86, access has to be given to the first megabyte of ram because that area + * contains bios code and data regions used by X and dosemu and similar apps. + * Access has to be given to non-kernel-ram areas as well, these contain the PCI + * mmio resources as well as potential bios/acpi data regions. + */ +int devmem_is_allowed(unsigned long pagenr) +{ + if (pagenr <= 256) + return 1; + if (!page_is_ram(pagenr)) + return 1; + return 0; +} + #ifdef CONFIG_HIGHMEM pte_t *kmap_pte; pgprot_t kmap_prot; diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 1ff7906..49c274e 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -664,6 +664,26 @@ EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid); #endif /* CONFIG_MEMORY_HOTPLUG */ +/* + * devmem_is_allowed() checks to see if /dev/mem access to a certain address + * is valid. The argument is a physical page number. + * + * + * On x86, access has to be given to the first megabyte of ram because that area + * contains bios code and data regions used by X and dosemu and similar apps. + * Access has to be given to non-kernel-ram areas as well, these contain the PCI + * mmio resources as well as potential bios/acpi data regions. + */ +int devmem_is_allowed(unsigned long pagenr) +{ + if (pagenr <= 256) + return 1; + if (!page_is_ram(pagenr)) + return 1; + return 0; +} + + static struct kcore_list kcore_mem, kcore_vmalloc, kcore_kernel, kcore_modules, kcore_vsyscall; diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 20070b7..dcf6e31 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -108,6 +108,30 @@ static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) } #endif +#ifdef CONFIG_NONPROMISC_DEVMEM +static inline int range_is_allowed(unsigned long from, unsigned long to) +{ + unsigned long cursor; + + cursor = from >> PAGE_SHIFT; + while ((cursor << PAGE_SHIFT) < to) { + if (!devmem_is_allowed(cursor)) { + printk(KERN_INFO "Program %s tried to read /dev/mem " + "between %lx->%lx.\n", + current->comm, from, to); + return 0; + } + cursor++; + } + return 1; +} +#else +static inline int range_is_allowed(unsigned long from, unsigned long to) +{ + return 1; +} +#endif + /* * This funcion reads the *physical* memory. The f_pos points directly to the * memory location. @@ -157,6 +181,8 @@ static ssize_t read_mem(struct file * file, char __user * buf, */ ptr = xlate_dev_mem_ptr(p); + if (!range_is_allowed(p, p+count)) + return -EPERM; if (copy_to_user(buf, ptr, sz)) return -EFAULT; buf += sz; @@ -214,6 +240,8 @@ static ssize_t write_mem(struct file * file, const char __user * buf, */ ptr = xlate_dev_mem_ptr(p); + if (!range_is_allowed(p, p+sz)) + return -EPERM; copied = copy_from_user(ptr, buf, sz); if (copied) { written += sz - copied; diff --git a/include/asm-x86/page.h b/include/asm-x86/page.h index 6724a4b..b381f4a 100644 --- a/include/asm-x86/page.h +++ b/include/asm-x86/page.h @@ -47,6 +47,7 @@ #ifndef __ASSEMBLY__ extern int page_is_ram(unsigned long pagenr); +extern int devmem_is_allowed(unsigned long pagenr); extern unsigned long max_pfn_mapped; |
