x86, hw_breakpoints: Fix racy access to ptrace breakpoints
authorFrederic Weisbecker <fweisbec@gmail.com>
Fri, 8 Apr 2011 15:29:36 +0000 (17:29 +0200)
committerFrederic Weisbecker <fweisbec@gmail.com>
Mon, 25 Apr 2011 15:32:40 +0000 (17:32 +0200)
commit87dc669ba25777b67796d7262c569429e58b1ed4
tree861710b50740b7d3924ce254963f3b4d26f0a514
parentbf26c018490c2fce7fe9b629083b96ce0e6ad019
x86, 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>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: v2.6.33.. <stable@kernel.org>
Link: http://lkml.kernel.org/r/1302284067-7860-3-git-send-email-fweisbec@gmail.com
arch/x86/kernel/ptrace.c