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seccomp: Whitelist `clock_adjtime` 

This only allows making the syscall. CAP_SYS_TIME is still required
for time adjustment (enforced by the kernel):

```
kernel/time/posix-timers.c:

1112 SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
1113                 struct __kernel_timex __user *, utx)
...
1121         err = do_clock_adjtime(which_clock, &ktx);

1100 int do_clock_adjtime(const clockid_t which_clock, struct __kernel_timex * ktx)
1101 {
...
1109         return kc->clock_adj(which_clock, ktx);

1299 static const struct k_clock clock_realtime = {
...
1304         .clock_adj              = posix_clock_realtime_adj,

188 static int posix_clock_realtime_adj(const clockid_t which_clock,
189                                     struct __kernel_timex *t)
190 {
191         return do_adjtimex(t);

kernel/time/timekeeping.c:

2312 int do_adjtimex(struct __kernel_timex *txc)
2313 {
...
2321         /* Validate the data before disabling interrupts */
2322         ret = timekeeping_validate_timex(txc);

2246 static int timekeeping_validate_timex(const struct __kernel_timex *txc)
2247 {
2248         if (txc->modes & ADJ_ADJTIME) {
...
2252                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
2253                     !capable(CAP_SYS_TIME))
2254                         return -EPERM;
2255         } else {
2256                 /* In order to modify anything, you gotta be super-user! */
2257                 if (txc->modes && !capable(CAP_SYS_TIME))
2258                         return -EPERM;

```

Fixes: https://github.com/moby/moby/issues/40919
Signed-off-by: Stanislav Levin <slev@altlinux.org>
This commit is contained in:
Stanislav Levin 2020-05-08 10:58:16 +03:00
parent cdf49f37ee
commit 5d3a9e4319
No known key found for this signature in database
GPG Key ID: ABABFE8D5D9A19E8
2 changed files with 4 additions and 0 deletions
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2
profiles/seccomp/default.json
View File

@ -65,6 +65,8 @@
"chmod",
"chown",
"chown32",
"clock_adjtime",
"clock_adjtime64",
"clock_getres",
"clock_getres_time64",
"clock_gettime",

2
profiles/seccomp/seccomp_default.go
View File

@ -58,6 +58,8 @@ func DefaultProfile() *types.Seccomp {
"chmod",
"chown",
"chown32",
"clock_adjtime",
"clock_adjtime64",
"clock_getres",
"clock_getres_time64",
"clock_gettime",