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| author | Ilya Leoshkevich <iii@linux.ibm.com> | 2019-08-16 12:53:00 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-09-16 11:44:05 +0200 |
| commit | d895a0f16fadb26d22ab531c49768f7642ae5c3e (patch) | |
| tree | d37c4f163bc37e8bce4150c075db214d7d1af389 /tools/testing/selftests/bpf/test_sysctl.c | |
| parent | af58e7ee6a8d83726ad8a2696e98d86400a7639c (diff) | |
| download | lwn-d895a0f16fadb26d22ab531c49768f7642ae5c3e.tar.gz lwn-d895a0f16fadb26d22ab531c49768f7642ae5c3e.zip | |
bpf: fix accessing bpf_sysctl.file_pos on s390
"ctx:file_pos sysctl:read write ok" fails on s390 with "Read value !=
nux". This is because verifier rewrites a complete 32-bit
bpf_sysctl.file_pos update to a partial update of the first 32 bits of
64-bit *bpf_sysctl_kern.ppos, which is not correct on big-endian
systems.
Fix by using an offset on big-endian systems.
Ditto for bpf_sysctl.file_pos reads. Currently the test does not detect
a problem there, since it expects to see 0, which it gets with high
probability in error cases, so change it to seek to offset 3 and expect
3 in bpf_sysctl.file_pos.
Fixes: e1550bfe0de4 ("bpf: Add file_pos field to bpf_sysctl ctx")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20190816105300.49035-1-iii@linux.ibm.com/
Diffstat (limited to 'tools/testing/selftests/bpf/test_sysctl.c')
| -rw-r--r-- | tools/testing/selftests/bpf/test_sysctl.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c index fc33ae36b760..4f8ec1f10a80 100644 --- a/tools/testing/selftests/bpf/test_sysctl.c +++ b/tools/testing/selftests/bpf/test_sysctl.c @@ -32,6 +32,7 @@ struct sysctl_test { enum bpf_attach_type attach_type; const char *sysctl; int open_flags; + int seek; const char *newval; const char *oldval; enum { @@ -140,7 +141,7 @@ static struct sysctl_test tests[] = { /* If (file_pos == X) */ BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_1, offsetof(struct bpf_sysctl, file_pos)), - BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0, 2), + BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 3, 2), /* return ALLOW; */ BPF_MOV64_IMM(BPF_REG_0, 1), @@ -153,6 +154,7 @@ static struct sysctl_test tests[] = { .attach_type = BPF_CGROUP_SYSCTL, .sysctl = "kernel/ostype", .open_flags = O_RDONLY, + .seek = 3, .result = SUCCESS, }, { @@ -1481,6 +1483,11 @@ static int access_sysctl(const char *sysctl_path, if (fd < 0) return fd; + if (test->seek && lseek(fd, test->seek, SEEK_SET) == -1) { + log_err("lseek(%d) failed", test->seek); + goto err; + } + if (test->open_flags == O_RDONLY) { char buf[128]; |