(resend with ppc list in cc)
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 <o...@redhat.com>
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Ingo Molnar <mi...@elte.hu>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
Cc: Will Deacon <will.dea...@arm.com>
Cc: Prasad <pra...@linux.vnet.ibm.com>
Cc: Paul Mundt <let...@linux-sh.org>
Cc: v2.6.33.. <sta...@kernel.org>
---
arch/powerpc/kernel/ptrace.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 55613e3..4edeeb3 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -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
--
1.7.3.2
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