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| author | Arnd Bergmann <arnd@arndb.de> | 2019-10-24 16:34:25 +0200 |
|---|---|---|
| committer | Arnd Bergmann <arnd@arndb.de> | 2019-12-18 18:07:31 +0100 |
| commit | 2d602bf28316e2f61a553f13d279f3d74c2e5189 (patch) | |
| tree | 26caf2d720c009f5f68b7f4db5e0079602b9e65c /kernel | |
| parent | 853bc0ab341b0c99619f83f4060dedcccad77b2a (diff) | |
| download | linux-2d602bf28316e2f61a553f13d279f3d74c2e5189.tar.gz linux-2d602bf28316e2f61a553f13d279f3d74c2e5189.tar.bz2 linux-2d602bf28316e2f61a553f13d279f3d74c2e5189.zip | |
acct: stop using get_seconds()
In 'struct acct', 'struct acct_v3', and 'struct taskstats' we have
a 32-bit 'ac_btime' field containing an absolute time value, which
will overflow in year 2106.
There are two possible ways to deal with it:
a) let it overflow and have user space code deal with reconstructing
the data based on the current time, or
b) truncate the times based on the range of the u32 type.
Neither of them solves the actual problem. Pick the second
one to best document what the issue is, and have someone
fix it in a future version.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/acct.c | 4 | ||||
| -rw-r--r-- | kernel/tsacct.c | 8 |
2 files changed, 8 insertions, 4 deletions
diff --git a/kernel/acct.c b/kernel/acct.c index 81f9831a7859..11ff4a596d6b 100644 --- a/kernel/acct.c +++ b/kernel/acct.c @@ -416,6 +416,7 @@ static void fill_ac(acct_t *ac) { struct pacct_struct *pacct = ¤t->signal->pacct; u64 elapsed, run_time; + time64_t btime; struct tty_struct *tty; /* @@ -448,7 +449,8 @@ static void fill_ac(acct_t *ac) } #endif do_div(elapsed, AHZ); - ac->ac_btime = get_seconds() - elapsed; + btime = ktime_get_real_seconds() - elapsed; + ac->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX); #if ACCT_VERSION==2 ac->ac_ahz = AHZ; #endif diff --git a/kernel/tsacct.c b/kernel/tsacct.c index 7be3e7530841..ab12616ee6fb 100644 --- a/kernel/tsacct.c +++ b/kernel/tsacct.c @@ -24,6 +24,7 @@ void bacct_add_tsk(struct user_namespace *user_ns, const struct cred *tcred; u64 utime, stime, utimescaled, stimescaled; u64 delta; + time64_t btime; BUILD_BUG_ON(TS_COMM_LEN < TASK_COMM_LEN); @@ -32,9 +33,10 @@ void bacct_add_tsk(struct user_namespace *user_ns, /* Convert to micro seconds */ do_div(delta, NSEC_PER_USEC); stats->ac_etime = delta; - /* Convert to seconds for btime */ - do_div(delta, USEC_PER_SEC); - stats->ac_btime = get_seconds() - delta; + /* Convert to seconds for btime (note y2106 limit) */ + btime = ktime_get_real_seconds() - div_u64(delta, USEC_PER_SEC); + stats->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX); + if (thread_group_leader(tsk)) { stats->ac_exitcode = tsk->exit_code; if (tsk->flags & PF_FORKNOEXEC) |