[valgrind] [Bug 496571] New: False positive for null key passed to bpf_map_get_next_key syscall.

[Ryan Mack]

https://bugs.kde.org/show_bug.cgi?id=496571

            Bug ID: 496571
           Summary: False positive for null key passed to
                    bpf_map_get_next_key syscall.
    Classification: Developer tools
           Product: valgrind
           Version: 3.22.0
          Platform: Ubuntu
                OS: Linux
            Status: REPORTED
          Severity: minor
          Priority: NOR
         Component: memcheck
          Assignee: jsew...@acm.org
          Reporter: rm...@uptycs.com
  Target Milestone: ---

The BPF function bpf_map_get_next_key takes a null key parameter to get the
first key in a map. Valgrind should not warn of an invalid pointer in this
case.

Locally tested fix:

diff --git a/coregrind/m_syswrap/syswrap-linux.c
b/coregrind/m_syswrap/syswrap-linux.c
index 177712117..9be77992c 100644
--- a/coregrind/m_syswrap/syswrap-linux.c
+++ b/coregrind/m_syswrap/syswrap-linux.c
@@ -12993,7 +12993,10 @@ PRE(sys_bpf)
             }
             /* Get size of key for this map. */
             if (bpf_map_get_sizes(attr->map_fd, &key_size, &value_size)) {
-               PRE_MEM_READ("bpf(attr->key)", attr->key, key_size);
+               /* Key is null when getting first entry in map. */
+               if (attr->key) {
+                  PRE_MEM_READ("bpf(attr->key)", attr->key, key_size);
+               }
                PRE_MEM_WRITE("bpf(attr->next_key)", attr->next_key, key_size);
             }
          }

-- 
You are receiving this mail because:
You are watching all bug changes.