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arm, 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: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Link: http://lkml.kernel.org/r/1302284067-7860-5-git-send-email-fweisbec@gmail.com
This commit is contained in:
Frederic Weisbecker 2011-04-08 17:29:36 +02:00
parent 07fa7a0a8a
commit bf0b8f4b55
1 changed files with 8 additions and 0 deletions
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8
arch/arm/kernel/ptrace.c
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@ -767,12 +767,20 @@ long arch_ptrace(struct task_struct *child, long request,
#ifdef CONFIG_HAVE_HW_BREAKPOINT #ifdef CONFIG_HAVE_HW_BREAKPOINT
case PTRACE_GETHBPREGS: case PTRACE_GETHBPREGS:
if (ptrace_get_breakpoints(child) < 0)
return -ESRCH;
ret = ptrace_gethbpregs(child, addr, ret = ptrace_gethbpregs(child, addr,
(unsigned long __user *)data); (unsigned long __user *)data);
ptrace_put_breakpoints(child);
break; break;
case PTRACE_SETHBPREGS: case PTRACE_SETHBPREGS:
if (ptrace_get_breakpoints(child) < 0)
return -ESRCH;
ret = ptrace_sethbpregs(child, addr, ret = ptrace_sethbpregs(child, addr,
(unsigned long __user *)data); (unsigned long __user *)data);
ptrace_put_breakpoints(child);
break; break;
#endif #endif