8 files changed, 74 insertions, 12 deletions

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
 
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 55613e33e263..4edeeb325429 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
diff --git a/arch/sh/kernel/ptrace_32.c b/arch/sh/kernel/ptrace_32.c
index 2130ca674e9b..3d7b209b2178 100644
--- a/arch/sh/kernel/ptrace_32.c
+++ b/arch/sh/kernel/ptrace_32.c
@@ -117,7 +117,11 @@ void user_enable_single_step(struct task_struct *child)
 
         set_tsk_thread_flag(child, TIF_SINGLESTEP);
 
+        if (ptrace_get_breakpoints(child) < 0)
+                return;
+
         set_single_step(child, pc);
+        ptrace_put_breakpoints(child);
 }
 
 void user_disable_single_step(struct task_struct *child)
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 45892dc4b72a..f65e5b521dbd 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -608,6 +608,9 @@ static int ptrace_write_dr7(struct task_struct *tsk, unsigned long data)
         unsigned len, type;
         struct perf_event *bp;
 
+        if (ptrace_get_breakpoints(tsk) < 0)
+                return -ESRCH;
+
         data &= ~DR_CONTROL_RESERVED;
         old_dr7 = ptrace_get_dr7(thread->ptrace_bps);
 restore:
@@ -655,6 +658,9 @@ restore:
                 }
                 goto restore;
         }
+
+        ptrace_put_breakpoints(tsk);
+
         return ((orig_ret < 0) ? orig_ret : rc);
 }
 
@@ -668,10 +674,17 @@ static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n)
 
         if (n < HBP_NUM) {
                 struct perf_event *bp;
+
+                if (ptrace_get_breakpoints(tsk) < 0)
+                        return -ESRCH;
+
                 bp = thread->ptrace_bps[n];
                 if (!bp)
-                        return 0;
-                val = bp->hw.info.address;
+                        val = 0;
+                else
+                        val = bp->hw.info.address;
+
+                ptrace_put_breakpoints(tsk);
         } else if (n == 6) {
                 val = thread->debugreg6;
          } else if (n == 7) {
@@ -686,6 +699,10 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
         struct perf_event *bp;
         struct thread_struct *t = &tsk->thread;
         struct perf_event_attr attr;
+        int err = 0;
+
+        if (ptrace_get_breakpoints(tsk) < 0)
+                return -ESRCH;
 
         if (!t->ptrace_bps[nr]) {
                 ptrace_breakpoint_init(&attr);
@@ -709,24 +726,23 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
                  * writing for the user. And anyway this is the previous
                  * behaviour.
                  */
-                if (IS_ERR(bp))
-                        return PTR_ERR(bp);
+                if (IS_ERR(bp)) {
+                        err = PTR_ERR(bp);
+                        goto put;
+                }
 
                 t->ptrace_bps[nr] = bp;
         } else {
-                int err;
-
                 bp = t->ptrace_bps[nr];
 
                 attr = bp->attr;
                 attr.bp_addr = addr;
                 err = modify_user_hw_breakpoint(bp, &attr);
-                if (err)
-                        return err;
         }
 
-
-        return 0;
+put:
+        ptrace_put_breakpoints(tsk);
+        return err;
 }
 
 /*
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
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 18d63cea2848..781abd137673 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1537,6 +1537,9 @@ struct task_struct {
                 unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
         } memcg_batch;
 #endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+        atomic_t ptrace_bp_refcnt;
+#endif
 };
 
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
diff --git a/kernel/exit.c b/kernel/exit.c
index f5d2f63bae0b..8dd874181542 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1016,7 +1016,7 @@ NORET_TYPE void do_exit(long code)
         /*
          * FIXME: do that only when needed, using sched_exit tracepoint
          */
-        flush_ptrace_hw_breakpoint(tsk);
+        ptrace_put_breakpoints(tsk);
 
         exit_notify(tsk, group_dead);
 #ifdef CONFIG_NUMA
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 0fc1eed28d27..dc7ab65f3b36 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -22,6 +22,7 @@
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 #include <linux/regset.h>
+#include <linux/hw_breakpoint.h>
 
 
 /*
@@ -879,3 +880,19 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
         return ret;
 }
 #endif  /* CONFIG_COMPAT */
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+int ptrace_get_breakpoints(struct task_struct *tsk)
+{
+        if (atomic_inc_not_zero(&tsk->ptrace_bp_refcnt))
+                return 0;
+
+        return -1;
+}
+
+void ptrace_put_breakpoints(struct task_struct *tsk)
+{
+        if (atomic_dec_and_test(&tsk->ptrace_bp_refcnt))
+                flush_ptrace_hw_breakpoint(tsk);
+}
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */