From ad133ba3dc283300e5b62b5b7211d2f39fbf6ee7 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 17 Nov 2008 15:39:47 +0100 Subject: sched, signals: fix the racy usage of ->signal in account_group_xxx/run_posix_cpu_timers Impact: fix potential NULL dereference Contrary to ad474caca3e2a0550b7ce0706527ad5ab389a4d4 changelog, other acct_group_xxx() helpers can be called after exit_notify() by timer tick. Thanks to Roland for pointing out this. Somehow I missed this simple fact when I read the original patch, and I am afraid I confused Frank during the discussion. Sorry. Fortunately, these helpers work with current, we can check ->exit_state to ensure that ->signal can't go away under us. Also, add the comment and compiler barrier to account_group_exec_runtime(), to make sure we load ->signal only once. Signed-off-by: Oleg Nesterov Signed-off-by: Ingo Molnar --- kernel/posix-cpu-timers.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'kernel/posix-cpu-timers.c') diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 153dcb2639c3..895337b16a24 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -1308,9 +1308,10 @@ static inline int task_cputime_expired(const struct task_cputime *sample, */ static inline int fastpath_timer_check(struct task_struct *tsk) { - struct signal_struct *sig = tsk->signal; + struct signal_struct *sig; - if (unlikely(!sig)) + /* tsk == current, ensure it is safe to use ->signal/sighand */ + if (unlikely(tsk->exit_state)) return 0; if (!task_cputime_zero(&tsk->cputime_expires)) { @@ -1323,6 +1324,8 @@ static inline int fastpath_timer_check(struct task_struct *tsk) if (task_cputime_expired(&task_sample, &tsk->cputime_expires)) return 1; } + + sig = tsk->signal; if (!task_cputime_zero(&sig->cputime_expires)) { struct task_cputime group_sample; -- cgit v1.2.3 From eccdaeafaea3ed115068ba55d01f22e486e5437d Mon Sep 17 00:00:00 2001 From: Petr Tesarik Date: Mon, 24 Nov 2008 15:46:31 +0100 Subject: posix-cpu-timers: fix clock_gettime with CLOCK_PROCESS_CPUTIME_ID Since CLOCK_PROCESS_CPUTIME_ID is in fact translated to -6, the switch statement in cpu_clock_sample_group() must first mask off the irrelevant bits, similar to cpu_clock_sample(). Signed-off-by: Petr Tesarik Signed-off-by: Thomas Gleixner -- posix-cpu-timers.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- kernel/posix-cpu-timers.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/posix-cpu-timers.c') diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 895337b16a24..4e5288a831de 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -311,7 +311,7 @@ static int cpu_clock_sample_group(const clockid_t which_clock, struct task_cputime cputime; thread_group_cputime(p, &cputime); - switch (which_clock) { + switch (CPUCLOCK_WHICH(which_clock)) { default: return -EINVAL; case CPUCLOCK_PROF: -- cgit v1.2.3