https://github.com/torvalds/linux
Revision 4c5640cb5f5a6fd780d99397eca028b575cb1206 authored by David Meybohm on 22 August 2005, 20:11:08 UTC, committed by Linus Torvalds on 23 August 2005, 18:44:29 UTC
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>
1 parent 3f024c1
Tip revision: 4c5640cb5f5a6fd780d99397eca028b575cb1206 authored by David Meybohm on 22 August 2005, 20:11:08 UTC
[PATCH] preempt race in getppid
[PATCH] preempt race in getppid
Tip revision: 4c5640c
File | Mode | Size |
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Documentation | ||
arch | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
scripts | ||
security | ||
sound | ||
usr | ||
COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 87.2 KB |
MAINTAINERS | -rw-r--r-- | 57.5 KB |
Makefile | -rw-r--r-- | 43.4 KB |
README | -rw-r--r-- | 14.2 KB |
REPORTING-BUGS | -rw-r--r-- | 3.0 KB |
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