uprobes: Do not delete uprobe if uprobe_unregister() fails

delete_uprobe() must not be called if register_for_each_vma(false)
fails to remove all breakpoints, __uprobe_unregister() is correct.
The problem is that register_for_each_vma(false) always returns 0
and thus this logic does not work.

1. Change verify_opcode() to return 0 rather than -EINVAL when
   unregister detects the !is_swbp insn, we can treat this case
   as success and currently unregister paths ignore the error
   code anyway.

2. Change remove_breakpoint() to propagate the error code from
   write_opcode().

3. Change register_for_each_vma(is_register => false) to remove
   as much breakpoints as possible but return non-zero if
   remove_breakpoint() fails at least once.

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

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 588a5575d64ce1e649b44a90f34f5d5d5869b8da..a1b466d17c1786e33aab081d7305c2d615dc2007 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -203,7 +203,7 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
                        return 0;
        } else {
                if (!is_swbp)           /* unregister: was it changed by us? */
-                       return -EINVAL;
+                       return 0;
        }
 
        return 1;
@@ -616,15 +616,15 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
        return ret;
 }
 
-static void
+static int
 remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
 {
        /* can happen if uprobe_register() fails */
        if (!test_bit(MMF_HAS_UPROBES, &mm->flags))
-               return;
+               return 0;
 
        set_bit(MMF_RECALC_UPROBES, &mm->flags);
-       set_orig_insn(&uprobe->arch, mm, vaddr);
+       return set_orig_insn(&uprobe->arch, mm, vaddr);
 }
 
 /*
@@ -740,7 +740,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
                struct mm_struct *mm = info->mm;
                struct vm_area_struct *vma;
 
-               if (err)
+               if (err && is_register)
                        goto free;
 
                down_write(&mm->mmap_sem);
@@ -756,7 +756,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
                if (is_register)
                        err = install_breakpoint(uprobe, mm, vma, info->vaddr);
                else
-                       remove_breakpoint(uprobe, mm, info->vaddr);
+                       err |= remove_breakpoint(uprobe, mm, info->vaddr);
 
  unlock:
                up_write(&mm->mmap_sem);