From: Hugh Dickins <hugh@veritas.com>
The p->signal check in account_system_time is insufficient. If the timer
interrupt hits near the end of exit_notify, after EXIT_ZOMBIE has been set,
another cpu may release_task (NULLifying p->signal) in between
account_system_time's check and check_rlimit's dereference. Nor should
account_it_prof risk send_sig. But surely account_user_time is safe?
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/kernel/sched.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)
diff -puN kernel/sched.c~mm-check_rlimit-oops-on-p-signal kernel/sched.c
--- 25/kernel/sched.c~mm-check_rlimit-oops-on-p-signal 2004-12-03 20:57:11.655866840 -0800
+++ 25-akpm/kernel/sched.c 2004-12-03 20:57:11.661865928 -0800
@@ -2348,8 +2348,7 @@ void account_user_time(struct task_struc
p->utime = cputime_add(p->utime, cputime);
/* Check for signals (SIGVTALRM, SIGPROF, SIGXCPU & SIGKILL). */
- if (likely(p->signal))
- check_rlimit(p, cputime);
+ check_rlimit(p, cputime);
account_it_virt(p, cputime);
account_it_prof(p, cputime);
@@ -2377,9 +2376,10 @@ void account_system_time(struct task_str
p->stime = cputime_add(p->stime, cputime);
/* Check for signals (SIGPROF, SIGXCPU & SIGKILL). */
- if (likely(p->signal))
+ if (likely(p->signal && p->exit_state < EXIT_ZOMBIE)) {
check_rlimit(p, cputime);
- account_it_prof(p, cputime);
+ account_it_prof(p, cputime);
+ }
/* Add system time to cpustat. */
tmp = cputime_to_cputime64(cputime);
_