Messages in this thread Patch in this message | | | Date | Thu, 15 Apr 2010 14:17:44 +0800 | Subject | Re: [PATCH] Kconfig: Make config Filter access to /dev/mem default y | From | wzt wzt <> |
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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 [+] 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.
>> >> 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/
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