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authorTejun Heo <tj@kernel.org>2011-02-10 15:01:22 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2011-02-17 15:37:03 -0800
commit16d0a1bf7848b5eaf520a9467e7c99c1e7064dfb (patch)
tree5136ecc9ca47d9d5b7c05a31bf993fce1734712f
parentbd577e06041f41ac77c8e44ad4047502483cc439 (diff)
ptrace: use safer wake up on ptrace_detach()
commit 01e05e9a90b8f4c3997ae0537e87720eb475e532 upstream. The wake_up_process() call in ptrace_detach() is spurious and not interlocked with the tracee state. IOW, the tracee could be running or sleeping in any place in the kernel by the time wake_up_process() is called. This can lead to the tracee waking up unexpectedly which can be dangerous. The wake_up is spurious and should be removed but for now reduce its toxicity by only waking up if the tracee is in TRACED or STOPPED state. This bug can possibly be used as an attack vector. I don't think it will take too much effort to come up with an attack which triggers oops somewhere. Most sleeps are wrapped in condition test loops and should be safe but we have quite a number of places where sleep and wakeup conditions are expected to be interlocked. Although the window of opportunity is tiny, ptrace can be used by non-privileged users and with some loading the window can definitely be extended and exploited. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Roland McGrath <roland@redhat.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--kernel/ptrace.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 23bd09cd042..05625f6c229 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -314,7 +314,7 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
child->exit_code = data;
dead = __ptrace_detach(current, child);
if (!child->exit_state)
- wake_up_process(child);
+ wake_up_state(child, TASK_TRACED | TASK_STOPPED);
}
write_unlock_irq(&tasklist_lock);