uprobes: Kill dup_mmap()->uprobe_mmap(), simplify uprobe_mmap/munmap

1. Kill dup_mmap()->uprobe_mmap(), it was only needed to calculate
   new_mm->uprobes_state.count removed by the previous patch.

   If the forking process has a pending uprobe (int3) in vma, it will
   be copied by copy_page_range(), note that it checks vma->anon_vma
   so "Don't copy ptes" is not possible after install_breakpoint()
   which does anon_vma_prepare().

2. Remove is_swbp_at_addr() and "int count" in uprobe_mmap(). Again,
   this was needed for uprobes_state.count.

   As a side effect this fixes the bug pointed out by Srikar,
   this code lacked the necessary put_uprobe().

3. uprobe_munmap() becomes a nop after the previous patch. Remove the
   meaningless code but do not remove the helper, we will need it.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

2 files changed, 3 insertions, 30 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 6f1664d217dc..ce59c100d65f 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1010,7 +1010,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
         struct list_head tmp_list;
         struct uprobe *uprobe, *u;
         struct inode *inode;
-        int ret, count;
+        int ret;
 
         if (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
                 return 0;
@@ -1023,8 +1023,6 @@ int uprobe_mmap(struct vm_area_struct *vma)
         build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
 
         ret = 0;
-        count = 0;
-
         list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
                 if (!ret) {
                         unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
@@ -1034,19 +1032,11 @@ int uprobe_mmap(struct vm_area_struct *vma)
                          * We can race against uprobe_register(), see the
                          * comment near uprobe_hash().
                          */
-                        if (ret == -EEXIST) {
+                        if (ret == -EEXIST)
                                 ret = 0;
-
-                                if (!is_swbp_at_addr(vma->vm_mm, vaddr))
-                                        continue;
-                        }
-
-                        if (!ret)
-                                count++;
                 }
                 put_uprobe(uprobe);
         }
-
         mutex_unlock(uprobes_mmap_hash(inode));
 
         return ret;
@@ -1057,27 +1047,13 @@ int uprobe_mmap(struct vm_area_struct *vma)
  */
 void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
 {
-        struct list_head tmp_list;
-        struct uprobe *uprobe, *u;
-        struct inode *inode;
-
         if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
                 return;
 
         if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
                 return;
 
-        inode = vma->vm_file->f_mapping->host;
-        if (!inode)
-                return;
-
-        mutex_lock(uprobes_mmap_hash(inode));
-        build_probe_list(inode, vma, start, end, &tmp_list);
-
-        list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
-                put_uprobe(uprobe);
-        }
-        mutex_unlock(uprobes_mmap_hash(inode));
+        /* TODO: unmapping uprobe(s) will need more work */
 }
 
 /* Slot allocation for XOL */
diff --git a/kernel/fork.c b/kernel/fork.c
index 2c8857e12855..912b6f6fe5b8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -454,9 +454,6 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 
                 if (retval)
                         goto out;
-
-                if (file)
-                        uprobe_mmap(tmp);
         }
         /* a new mm has just been created */
         arch_dup_mmap(oldmm, mm);