Messages in this thread Patch in this message | | | Date | Wed, 4 May 2011 20:29:19 GMT | From | tip-bot for Frederic Weisbecker <> | Subject | [tip:perf/urgent] powerpc, hw_breakpoints: Fix racy access to ptrace breakpoints |
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Commit-ID: 07fa7a0a8a586c01a8b416358c7012dcb9dc688d Gitweb: http://git.kernel.org/tip/07fa7a0a8a586c01a8b416358c7012dcb9dc688d Author: Frederic Weisbecker <fweisbec@gmail.com> AuthorDate: Fri, 8 Apr 2011 17:29:36 +0200 Committer: Frederic Weisbecker <fweisbec@gmail.com> CommitDate: Mon, 25 Apr 2011 17:33:54 +0200
powerpc, hw_breakpoints: Fix racy access to ptrace breakpoints
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 --- 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
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