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Message-ID: <CAGXu5j+41UTPkvAArwUjA+BHv3S+55iHEb40BF1=m7_5g-NkHQ@mail.gmail.com>
Date: Mon, 2 Nov 2015 11:49:27 -0800
From: Kees Cook <keescook@...omium.org>
To: Shuah Khan <shuahkh@....samsung.com>
Cc: Robert Sesek <rsesek@...gle.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selftests/seccomp: Be more precise with syscall arguments.
On Mon, Nov 2, 2015 at 10:50 AM, Robert Sesek <rsesek@...gle.com> wrote:
> Certain syscall emulation layers strictly check that the number of
> arguments match what the syscall handler expects. The KILL_one_arg_one and
> KILL_one_arg_six tests passed more parameters than expected to various
> syscalls, causing failures in this emulation mode. Instead, test using
> syscalls that take the appropriate number of arguments.
>
> Signed-off-by: Robert Sesek <rsesek@...gle.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Looks great, thanks!
Shuah, can you take this into the selftests tree?
-Kees
> ---
> tools/testing/selftests/seccomp/seccomp_bpf.c | 46 ++++++++++++++++++++-------
> 1 file changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index e7bc5d3..e38cc54 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -29,6 +29,9 @@
> #include <linux/elf.h>
> #include <sys/uio.h>
> #include <sys/utsname.h>
> +#include <sys/fcntl.h>
> +#include <sys/mman.h>
> +#include <sys/times.h>
>
> #define _GNU_SOURCE
> #include <unistd.h>
> @@ -429,14 +432,16 @@ TEST_SIGNAL(KILL_one, SIGSYS)
>
> TEST_SIGNAL(KILL_one_arg_one, SIGSYS)
> {
> + void *fatal_address;
> struct sock_filter filter[] = {
> BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
> offsetof(struct seccomp_data, nr)),
> - BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
> + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_times, 1, 0),
> BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
> /* Only both with lower 32-bit for now. */
> BPF_STMT(BPF_LD|BPF_W|BPF_ABS, syscall_arg(0)),
> - BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x0C0FFEE, 0, 1),
> + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K,
> + (unsigned long)&fatal_address, 0, 1),
> BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
> BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
> };
> @@ -446,7 +451,8 @@ TEST_SIGNAL(KILL_one_arg_one, SIGSYS)
> };
> long ret;
> pid_t parent = getppid();
> - pid_t pid = getpid();
> + struct tms timebuf;
> + clock_t clock = times(&timebuf);
>
> ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
> ASSERT_EQ(0, ret);
> @@ -455,17 +461,22 @@ TEST_SIGNAL(KILL_one_arg_one, SIGSYS)
> ASSERT_EQ(0, ret);
>
> EXPECT_EQ(parent, syscall(__NR_getppid));
> - EXPECT_EQ(pid, syscall(__NR_getpid));
> - /* getpid() should never return. */
> - EXPECT_EQ(0, syscall(__NR_getpid, 0x0C0FFEE));
> + EXPECT_LE(clock, syscall(__NR_times, &timebuf));
> + /* times() should never return. */
> + EXPECT_EQ(0, syscall(__NR_times, &fatal_address));
> }
>
> TEST_SIGNAL(KILL_one_arg_six, SIGSYS)
> {
> +#ifndef __NR_mmap2
> + int sysno = __NR_mmap;
> +#else
> + int sysno = __NR_mmap2;
> +#endif
> struct sock_filter filter[] = {
> BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
> offsetof(struct seccomp_data, nr)),
> - BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
> + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, sysno, 1, 0),
> BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
> /* Only both with lower 32-bit for now. */
> BPF_STMT(BPF_LD|BPF_W|BPF_ABS, syscall_arg(5)),
> @@ -479,7 +490,8 @@ TEST_SIGNAL(KILL_one_arg_six, SIGSYS)
> };
> long ret;
> pid_t parent = getppid();
> - pid_t pid = getpid();
> + int fd;
> + void *map1, *map2;
>
> ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
> ASSERT_EQ(0, ret);
> @@ -487,10 +499,22 @@ TEST_SIGNAL(KILL_one_arg_six, SIGSYS)
> ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
> ASSERT_EQ(0, ret);
>
> + fd = open("/dev/zero", O_RDONLY);
> + ASSERT_NE(-1, fd);
> +
> EXPECT_EQ(parent, syscall(__NR_getppid));
> - EXPECT_EQ(pid, syscall(__NR_getpid));
> - /* getpid() should never return. */
> - EXPECT_EQ(0, syscall(__NR_getpid, 1, 2, 3, 4, 5, 0x0C0FFEE));
> + map1 = (void *)syscall(sysno,
> + NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE, fd, PAGE_SIZE);
> + EXPECT_NE(MAP_FAILED, map1);
> + /* mmap2() should never return. */
> + map2 = (void *)syscall(sysno,
> + NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE, fd, 0x0C0FFEE);
> + EXPECT_EQ(MAP_FAILED, map2);
> +
> + /* The test failed, so clean up the resources. */
> + munmap(map1, PAGE_SIZE);
> + munmap(map2, PAGE_SIZE);
> + close(fd);
> }
>
> /* TODO(wad) add 64-bit versus 32-bit arg tests. */
> --
> 2.6.0.rc2.230.g3dd15c0
>
--
Kees Cook
Chrome OS Security
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