3 files changed, 33 insertions, 3 deletions

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 2615c4d7788d..4f628a6fc5b4 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -97,6 +97,8 @@ extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_con
 extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
 extern int uprobe_mmap(struct vm_area_struct *vma);
 extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
+extern void uprobe_start_dup_mmap(void);
+extern void uprobe_end_dup_mmap(void);
 extern void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm);
 extern void uprobe_free_utask(struct task_struct *t);
 extern void uprobe_copy_process(struct task_struct *t);
@@ -127,6 +129,12 @@ static inline void
 uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
 {
 }
+static inline void uprobe_start_dup_mmap(void)
+{
+}
+static inline void uprobe_end_dup_mmap(void)
+{
+}
 static inline void
 uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
 {
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 5ce99cfd2e6e..dea7acfbb071 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -33,6 +33,7 @@
 #include <linux/ptrace.h>       /* user_enable_single_step */
 #include <linux/kdebug.h>       /* notifier mechanism */
 #include "../../mm/internal.h"  /* munlock_vma_page */
+#include <linux/percpu-rwsem.h>
 
 #include <linux/uprobes.h>
 
@@ -71,6 +72,8 @@ static struct mutex uprobes_mutex[UPROBES_HASH_SZ];
 static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
 #define uprobes_mmap_hash(v)    (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
 
+static struct percpu_rw_semaphore dup_mmap_sem;
+
 /*
  * uprobe_events allows us to skip the uprobe_mmap if there are no uprobe
  * events active at this time.  Probably a fine grained per inode count is
@@ -766,10 +769,13 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
         struct map_info *info;
         int err = 0;
 
+        percpu_down_write(&dup_mmap_sem);
         info = build_map_info(uprobe->inode->i_mapping,
                                         uprobe->offset, is_register);
-        if (IS_ERR(info))
-                return PTR_ERR(info);
+        if (IS_ERR(info)) {
+                err = PTR_ERR(info);
+                goto out;
+        }
 
         while (info) {
                 struct mm_struct *mm = info->mm;
@@ -799,7 +805,8 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
                 mmput(mm);
                 info = free_map_info(info);
         }
-
+ out:
+        percpu_up_write(&dup_mmap_sem);
         return err;
 }
 
@@ -1131,6 +1138,16 @@ void uprobe_clear_state(struct mm_struct *mm)
         kfree(area);
 }
 
+void uprobe_start_dup_mmap(void)
+{
+        percpu_down_read(&dup_mmap_sem);
+}
+
+void uprobe_end_dup_mmap(void)
+{
+        percpu_up_read(&dup_mmap_sem);
+}
+
 void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
 {
         newmm->uprobes_state.xol_area = NULL;
@@ -1597,6 +1614,9 @@ static int __init init_uprobes(void)
                 mutex_init(&uprobes_mmap_mutex[i]);
         }
 
+        if (percpu_init_rwsem(&dup_mmap_sem))
+                return -ENOMEM;
+
         return register_die_notifier(&uprobe_exception_nb);
 }
 module_init(init_uprobes);
diff --git a/kernel/fork.c b/kernel/fork.c
index 8b20ab7d3aa2..c497e57aa654 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -352,6 +352,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
         unsigned long charge;
         struct mempolicy *pol;
 
+        uprobe_start_dup_mmap();
         down_write(&oldmm->mmap_sem);
         flush_cache_dup_mm(oldmm);
         uprobe_dup_mmap(oldmm, mm);
@@ -469,6 +470,7 @@ out:
         up_write(&mm->mmap_sem);
         flush_tlb_mm(oldmm);
         up_write(&oldmm->mmap_sem);
+        uprobe_end_dup_mmap();
         return retval;
 fail_nomem_anon_vma_fork:
         mpol_put(pol);