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powerpc, hw_breakpoints: Fix racy access to ptrace breakpoints

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While the tracer accesses ptrace breakpoints, the child task may
concurrently exit due to a SIGKILL and thus release its breakpoints
at the same time. We can then dereference some freed pointers.

To fix this, hold a reference on the child breakpoints before
manipulating them.

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Prasad <prasad@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: v2.6.33.. <stable@kernel.org>
Link: http://lkml.kernel.org/r/1302284067-7860-4-git-send-email-fweisbec@gmail.com
This commit is contained in:
Frederic Weisbecker 2011-04-08 17:29:36 +02:00
parent 87dc669ba2
commit 07fa7a0a8a
1 changed files with 3 additions and 0 deletions
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3
arch/powerpc/kernel/ptrace.c
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@ -1591,7 +1591,10 @@ long arch_ptrace(struct task_struct *child, long request,
}
case PTRACE_SET_DEBUGREG:
if (ptrace_get_breakpoints(child) < 0)
return -ESRCH;
ret = ptrace_set_debugreg(child, addr, data);
ptrace_put_breakpoints(child);
break;
#ifdef CONFIG_PPC64