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David Meybohm 4c5640cb5f [PATCH] preempt race in getppid ... With CONFIG_PREEMPT && !CONFIG_SMP, it's possible for sys_getppid to return a bogus value if the parent's task_struct gets reallocated after current->group_leader->real_parent is read: asmlinkage long sys_getppid(void) { int pid; struct task_struct *me = current; struct task_struct *parent; parent = me->group_leader->real_parent; RACE HERE => for (;;) { pid = parent->tgid; #ifdef CONFIG_SMP { struct task_struct *old = parent; /* * Make sure we read the pid before re-reading the * parent pointer: */ smp_rmb(); parent = me->group_leader->real_parent; if (old != parent) continue; } #endif break; } return pid; } If the process gets preempted at the indicated point, the parent process can go ahead and call exit() and then get wait()'d on to reap its task_struct. When the preempted process gets resumed, it will not do any further checks of the parent pointer on !CONFIG_SMP: it will read the bad pid and return. So, the same algorithm used when SMP is enabled should be used when preempt is enabled, which will recheck ->real_parent in this case. Signed-off-by: David Meybohm <dmeybohmlkml@bellsouth.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>		20 years ago
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irq	…
power	…
Kconfig.hz	…
Kconfig.preempt	…
Makefile	…
acct.c	…
audit.c	…
auditsc.c	…
capability.c	…
compat.c	…
configs.c	…
cpu.c	…
cpuset.c	[PATCH] cpuset release ABBA deadlock fix	20 years ago
crash_dump.c	[PATCH] kernel/crash_dump.c: add kerneldoc	20 years ago
dma.c	…
exec_domain.c	…
exit.c	[PATCH] revert "timer exit cleanup"	20 years ago
extable.c	…
fork.c	…
futex.c	…
intermodule.c	…
itimer.c	…
kallsyms.c	…
kexec.c	…
kfifo.c	…
kmod.c	…
kprobes.c	…
ksysfs.c	…
kthread.c	…
module.c	[PATCH] Module per-cpu alignment cannot always be met	20 years ago
panic.c	…
params.c	…
pid.c	…
posix-cpu-timers.c	…
posix-timers.c	[PATCH] revert "timer exit cleanup"	20 years ago
printk.c	…
profile.c	…
ptrace.c	…
rcupdate.c	…
resource.c	…
sched.c	[PATCH] Make RLIMIT_NICE ranges consistent with getpriority(2)	20 years ago
seccomp.c	…
signal.c	[PATCH] NPTL signal delivery deadlock fix	20 years ago
softirq.c	[PATCH] revert bogus softirq changes	20 years ago
spinlock.c	…
stop_machine.c	…
sys.c	[PATCH] Remove suspend() calls from shutdown path	20 years ago
sys_ni.c	[PATCH] remove sys_set_zone_reclaim()	20 years ago
sysctl.c	…
time.c	[PATCH] clean up inline static vs static inline	20 years ago
timer.c	[PATCH] preempt race in getppid	20 years ago
uid16.c	…
user.c	…
wait.c	…
workqueue.c	[PATCH] remove name length check in a workqueue	20 years ago