Messages in this thread | | | Date | Thu, 15 Apr 2010 14:28:30 +0800 | Subject | Re: [PATCH] Kconfig: Make config Filter access to /dev/mem default y | From | Xiaotian Feng <> |
| |
On Thu, Apr 15, 2010 at 2:17 PM, wzt wzt <wzt.wzt@gmail.com> wrote: > On Thu, Apr 15, 2010 at 2:12 PM, Xiaotian Feng <xtfeng@gmail.com> wrote: >> On Tue, Apr 13, 2010 at 10:52 AM, <wzt.wzt@gmail.com> wrote: >>> Recently, most company start use >=2.6.31 kernels to replace redhat kernels. >>> But the config "Filter access to /dev/mem" is "default n", that allows kernel >>> rootkit using /dev/mem again. it could access all kernel memory default. Most >>> administrator don't known the "Filter access to /dev/mem" is "defult N", when >>> he compiles the kernel, it's easily to be attacked by rootkit. >> >> Have you ever successfully attack by this way? > > [root@localhost zealot]# ./zealot
so you're running rootkit as a root user?
> [+] Found HISTSIZE. [SAFE] > [+] Check md5 values. [SAFE] > [+] eth0 was not set promsic. [SAFE] > [+] Not found raw socket. [SAFE] > system_call addr changed to 0xc04028a0,sys_call_table addr changed to > 0xc0675130,Found dr rootkit!,system call sys_execve addr changed to > 0xc0401582,system call sys_olduname addr changed to 0xc0405989,system > call sys_fork addr changed to 0xc0407bbb > > It's a host ids i wrote, it could search all kernel memory using /dev/mem. ok? > > some of the code here: > static void *kmap(unsigned long off, unsigned long count) > { > int fd; > void *p; > > fd = open(DEV_MEM, O_RDWR); > if (fd < 3) { > DbgPrint("open %s failed.\n", DEV_MEM); > dup2(fd, 3); > close(fd); > fd = 3; > } > > p = mmap(NULL, ALIGNUP(count + 4097), PROT_READ | PROT_WRITE, > MAP_SHARED, fd, ALIGNDOWN(off) & 0x0fffffff); > if (p == MAP_FAILED) > { > mem_support_flag = 1; > fprintf(stdout, "[-] /dev/mem cannot be read or write.\n"); > > DbgPrint("mmap failture, errno %d\n", errno); > close(fd); > return NULL; > } > > close(fd); > return p; > } > >>If CONFIG_STRICT_DEVMEM >> is not set, the /dev/mem access is filtered in pat code. > please point it, thanks. >
Years ago, someone sent the same patch. check http://lkml.org/lkml/2008/11/7/361
>>> >>> Signed-off-by: Zhitong Wang <zhitong.wangzt@alibaba-inc.com> >>> >>> --- >>> arch/x86/Kconfig.debug | 3 ++- >>> arch/x86/configs/i386_defconfig | 2 +- >>> arch/x86/configs/x86_64_defconfig | 2 +- >>> 3 files changed, 4 insertions(+), 3 deletions(-) >>> >>> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug >>> index bc01e3e..733aea6 100644 >>> --- a/arch/x86/Kconfig.debug >>> +++ b/arch/x86/Kconfig.debug >>> @@ -7,6 +7,7 @@ source "lib/Kconfig.debug" >>> >>> config STRICT_DEVMEM >>> bool "Filter access to /dev/mem" >>> + default y >>> ---help--- >>> If this option is disabled, you allow userspace (root) access to all >>> of memory, including kernel and userspace memory. Accidental >>> @@ -20,7 +21,7 @@ config STRICT_DEVMEM >>> This is sufficient for dosemu and X and all common users of >>> /dev/mem. >>> >>> - If in doubt, say Y. >>> + If in doubt, say N. >>> >>> config X86_VERBOSE_BOOTUP >>> bool "Enable verbose x86 bootup info messages" >>> diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig >>> index d28fad1..95c85a8 100644 >>> --- a/arch/x86/configs/i386_defconfig >>> +++ b/arch/x86/configs/i386_defconfig >>> @@ -2386,7 +2386,7 @@ CONFIG_PROVIDE_OHCI1394_DMA_INIT=y >>> # CONFIG_SAMPLES is not set >>> CONFIG_HAVE_ARCH_KGDB=y >>> # CONFIG_KGDB is not set >>> -# CONFIG_STRICT_DEVMEM is not set >>> +CONFIG_STRICT_DEVMEM=y >>> CONFIG_X86_VERBOSE_BOOTUP=y >>> CONFIG_EARLY_PRINTK=y >>> CONFIG_EARLY_PRINTK_DBGP=y >>> diff --git a/arch/x86/configs/x86_64_defconfig b/arch/x86/configs/x86_64_defconfig >>> index 6c86acd..659bfe7 100644 >>> --- a/arch/x86/configs/x86_64_defconfig >>> +++ b/arch/x86/configs/x86_64_defconfig >>> @@ -2360,7 +2360,7 @@ CONFIG_PROVIDE_OHCI1394_DMA_INIT=y >>> # CONFIG_SAMPLES is not set >>> CONFIG_HAVE_ARCH_KGDB=y >>> # CONFIG_KGDB is not set >>> -# CONFIG_STRICT_DEVMEM is not set >>> +CONFIG_STRICT_DEVMEM=y >>> CONFIG_X86_VERBOSE_BOOTUP=y >>> CONFIG_EARLY_PRINTK=y >>> CONFIG_EARLY_PRINTK_DBGP=y >>> -- >>> 1.6.5.3 >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> Please read the FAQ at http://www.tux.org/lkml/ >>> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |