uprobes/sdt: Prevent multiple reference counter for same uprobe

We assume to have only one reference counter for one uprobe.
Don't allow user to register multiple uprobes having same
inode+offset but different reference counter.

Link: http://lkml.kernel.org/r/20180820044250.11659-3-ravi.bangoria@linux.ibm.com

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 934feb39f6be..96fb51f3994f 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -679,6 +679,16 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe)
         return u;
 }
 
+static void
+ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe)
+{
+        pr_warn("ref_ctr_offset mismatch. inode: 0x%lx offset: 0x%llx "
+                "ref_ctr_offset(old): 0x%llx ref_ctr_offset(new): 0x%llx\n",
+                uprobe->inode->i_ino, (unsigned long long) uprobe->offset,
+                (unsigned long long) cur_uprobe->ref_ctr_offset,
+                (unsigned long long) uprobe->ref_ctr_offset);
+}
+
 static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
                                    loff_t ref_ctr_offset)
 {
@@ -698,6 +708,12 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
         cur_uprobe = insert_uprobe(uprobe);
         /* a uprobe exists for this inode:offset combination */
         if (cur_uprobe) {
+                if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) {
+                        ref_ctr_mismatch_warn(cur_uprobe, uprobe);
+                        put_uprobe(cur_uprobe);
+                        kfree(uprobe);
+                        return ERR_PTR(-EINVAL);
+                }
                 kfree(uprobe);
                 uprobe = cur_uprobe;
         }
@@ -1112,6 +1128,9 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
         uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
         if (!uprobe)
                 return -ENOMEM;
+        if (IS_ERR(uprobe))
+                return PTR_ERR(uprobe);
+
         /*
          * We can race with uprobe_unregister()->delete_uprobe().
          * Check uprobe_is_active() and retry if it is false.