From 2d602bf28316e2f61a553f13d279f3d74c2e5189 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 24 Oct 2019 16:34:25 +0200 Subject: 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 --- include/uapi/linux/taskstats.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/uapi/linux/taskstats.h') diff --git a/include/uapi/linux/taskstats.h b/include/uapi/linux/taskstats.h index 5e8ca16a9079..7d3ea366e93b 100644 --- a/include/uapi/linux/taskstats.h +++ b/include/uapi/linux/taskstats.h @@ -112,6 +112,7 @@ struct taskstats { __u32 ac_gid; /* Group ID */ __u32 ac_pid; /* Process ID */ __u32 ac_ppid; /* Parent process ID */ + /* __u32 range means times from 1970 to 2106 */ __u32 ac_btime; /* Begin time [sec since 1970] */ __u64 ac_etime __attribute__((aligned(8))); /* Elapsed time [usec] */ -- cgit v1.3-8-gc7d7 From 352c912b0a525977a8e6fa1f87c15d9f71943642 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 24 Oct 2019 16:47:56 +0200 Subject: tsacct: add 64-bit btime field As there is only a 32-bit ac_btime field in taskstat and we should handle dates after the overflow, add a new field with the same information but 64-bit width that can hold a full time64_t. Signed-off-by: Arnd Bergmann --- include/uapi/linux/taskstats.h | 5 ++++- kernel/tsacct.c | 1 + 2 files changed, 5 insertions(+), 1 deletion(-) (limited to 'include/uapi/linux/taskstats.h') diff --git a/include/uapi/linux/taskstats.h b/include/uapi/linux/taskstats.h index 7d3ea366e93b..ccbd08709321 100644 --- a/include/uapi/linux/taskstats.h +++ b/include/uapi/linux/taskstats.h @@ -34,7 +34,7 @@ */ -#define TASKSTATS_VERSION 9 +#define TASKSTATS_VERSION 10 #define TS_COMM_LEN 32 /* should be >= TASK_COMM_LEN * in linux/sched.h */ @@ -169,6 +169,9 @@ struct taskstats { /* Delay waiting for thrashing page */ __u64 thrashing_count; __u64 thrashing_delay_total; + + /* v10: 64-bit btime to avoid overflow */ + __u64 ac_btime64; /* 64-bit begin time */ }; diff --git a/kernel/tsacct.c b/kernel/tsacct.c index ab12616ee6fb..257ffb993ea2 100644 --- a/kernel/tsacct.c +++ b/kernel/tsacct.c @@ -36,6 +36,7 @@ void bacct_add_tsk(struct user_namespace *user_ns, /* 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); + stats->ac_btime64 = btime; if (thread_group_leader(tsk)) { stats->ac_exitcode = tsk->exit_code; -- cgit v1.3-8-gc7d7