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authorFrederic Weisbecker <fweisbec@gmail.com>2011-04-07 18:53:20 +0400
committerFrederic Weisbecker <fweisbec@gmail.com>2011-04-25 19:28:24 +0400
commitbf26c018490c2fce7fe9b629083b96ce0e6ad019 (patch)
treeff595f6268cb6fc675beb6accf6abb0701829443 /include/linux/ptrace.h
parentf4929bd37208540c2c6f416e9035ff1938f2dbc6 (diff)
downloadlinux-bf26c018490c2fce7fe9b629083b96ce0e6ad019.tar.xz
ptrace: Prepare to fix racy accesses on task breakpoints
When a task is traced and is in a stopped state, the tracer may execute a ptrace request to examine the tracee state and get its task struct. Right after, the tracee can be killed and thus its breakpoints released. This can happen concurrently when the tracer is in the middle of reading or modifying these breakpoints, leading to dereferencing a freed pointer. Hence, to prepare the fix, create a generic breakpoint reference holding API. When a reference on the breakpoints of a task is held, the breakpoints won't be released until the last reference is dropped. After that, no more ptrace request on the task's breakpoints can be serviced for the tracer. 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/1302284067-7860-2-git-send-email-fweisbec@gmail.com
Diffstat (limited to 'include/linux/ptrace.h')
-rw-r--r--include/linux/ptrace.h13
1 files changed, 12 insertions, 1 deletions
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index a1147e5dd245..9178d5cc0b01 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -189,6 +189,10 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
child->ptrace = current->ptrace;
__ptrace_link(child, current->parent);
}
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+ atomic_set(&child->ptrace_bp_refcnt, 1);
+#endif
}
/**
@@ -350,6 +354,13 @@ extern int task_current_syscall(struct task_struct *target, long *callno,
unsigned long args[6], unsigned int maxargs,
unsigned long *sp, unsigned long *pc);
-#endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+extern int ptrace_get_breakpoints(struct task_struct *tsk);
+extern void ptrace_put_breakpoints(struct task_struct *tsk);
+#else
+static inline void ptrace_put_breakpoints(struct task_struct *tsk) { }
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+
+#endif /* __KERNEL */
#endif