From bf0b8f4b55e591ba417c2dbaff42769e1fc773b0 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 8 Apr 2011 17:29:36 +0200 Subject: arm, 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 Signed-off-by: Frederic Weisbecker Acked-by: Will Deacon Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Prasad Cc: Paul Mundt Link: http://lkml.kernel.org/r/1302284067-7860-5-git-send-email-fweisbec@gmail.com --- arch/arm/kernel/ptrace.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/arm/kernel') diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 2bf27f364d09..8182f45ca493 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -767,12 +767,20 @@ long arch_ptrace(struct task_struct *child, long request, #ifdef CONFIG_HAVE_HW_BREAKPOINT case PTRACE_GETHBPREGS: + if (ptrace_get_breakpoints(child) < 0) + return -ESRCH; + ret = ptrace_gethbpregs(child, addr, (unsigned long __user *)data); + ptrace_put_breakpoints(child); break; case PTRACE_SETHBPREGS: + if (ptrace_get_breakpoints(child) < 0) + return -ESRCH; + ret = ptrace_sethbpregs(child, addr, (unsigned long __user *)data); + ptrace_put_breakpoints(child); break; #endif -- cgit v1.2.3-59-g8ed1b