vppinfra: asan: fix overflow support

In some part of VPP we are accessing memory past what was allocated for
efficiency when we know it is safe to do so. We need to tell ASan about
it so it does not complain.
The initial attempt was too simple and could not manage cases where the
poisoned memory was scattered. This new attempt is more robust as we
save and restore the full shadow state.
Note it will still not work properly if we poison/unpoison memory while
in an overflow context, but this should not be a big issue as overflow
should only be temporary.

Type: fix

Change-Id: I636f44eb59aa8455a4d13929a3791b56619af7b4
Signed-off-by: Benoît Ganne <bganne@cisco.com>

3 files changed, 89 insertions, 14 deletions

diff --git a/src/vppinfra/CMakeLists.txt b/src/vppinfra/CMakeLists.txt
index 6da1fa2a0a1..64420b96676 100644
--- a/src/vppinfra/CMakeLists.txt
+++ b/src/vppinfra/CMakeLists.txt
@@ -77,6 +77,7 @@ set(VPPINFRA_SRCS
   random.c
   random_isaac.c
   rbtree.c
+  sanitizer.c
   serialize.c
   socket.c
   std-formats.c
diff --git a/src/vppinfra/sanitizer.c b/src/vppinfra/sanitizer.c
new file mode 100644
index 00000000000..fab1cdca136
--- /dev/null
+++ b/src/vppinfra/sanitizer.c
@@ -0,0 +1,7 @@
+#ifdef CLIB_SANITIZE_ADDR
+
+#include <vppinfra/sanitizer.h>
+
+__clib_export clib_sanitizer_main_t sanitizer_main = { .shadow_scale = ~0 };
+
+#endif /* CLIB_SANITIZE_ADDR */
diff --git a/src/vppinfra/sanitizer.h b/src/vppinfra/sanitizer.h
index db4daea978d..658d8281230 100644
--- a/src/vppinfra/sanitizer.h
+++ b/src/vppinfra/sanitizer.h
@@ -5,25 +5,92 @@
 
 #include <sanitizer/asan_interface.h>
 #include <vppinfra/clib.h>
+#include <vppinfra/error_bootstrap.h>
+
+typedef struct
+{
+  size_t shadow_scale;
+  size_t shadow_offset;
+} clib_sanitizer_main_t;
+
+extern clib_sanitizer_main_t sanitizer_main;
 
 #define CLIB_NOSANITIZE_ADDR    __attribute__((no_sanitize_address))
 #define CLIB_MEM_POISON(a, s)   ASAN_POISON_MEMORY_REGION((a), (s))
 #define CLIB_MEM_UNPOISON(a, s) ASAN_UNPOISON_MEMORY_REGION((a), (s))
 
-#define CLIB_MEM_OVERFLOW(f, src, n) \
-  ({ \
-   typeof (f) clib_mem_overflow_ret__; \
-   const void *clib_mem_overflow_src__ = (src); \
-   size_t clib_mem_overflow_n__ = (n); \
-   const void *clib_mem_overflow_start__ = __asan_region_is_poisoned((void *)clib_mem_overflow_src__, clib_mem_overflow_n__); \
-   clib_mem_overflow_n__ -= (size_t)(clib_mem_overflow_start__ - clib_mem_overflow_src__); \
-   if (clib_mem_overflow_start__) \
-     CLIB_MEM_UNPOISON(clib_mem_overflow_start__, clib_mem_overflow_n__); \
-   clib_mem_overflow_ret__ = f; \
-   if (clib_mem_overflow_start__) \
-     CLIB_MEM_POISON(clib_mem_overflow_start__, clib_mem_overflow_n__); \
-   clib_mem_overflow_ret__; \
-   })
+#define CLIB_MEM_OVERFLOW_MAX 64
+
+static_always_inline void
+sanitizer_unpoison__ (u64 *restrict *shadow_ptr, size_t *shadow_len,
+		      const void *ptr, size_t len)
+{
+  size_t scale, off;
+
+  if (PREDICT_FALSE (~0 == sanitizer_main.shadow_scale))
+    __asan_get_shadow_mapping (&sanitizer_main.shadow_scale,
+			       &sanitizer_main.shadow_offset);
+
+  scale = sanitizer_main.shadow_scale;
+  off = sanitizer_main.shadow_offset;
+
+  /* compute the shadow address and length */
+  *shadow_len = len >> scale;
+  ASSERT (*shadow_len <= CLIB_MEM_OVERFLOW_MAX);
+  *shadow_ptr = (void *) (((clib_address_t) ptr >> scale) + off);
+}
+
+static_always_inline CLIB_NOSANITIZE_ADDR void
+sanitizer_unpoison_push__ (u64 *restrict shadow, const void *ptr, size_t len)
+{
+  u64 *restrict shadow_ptr;
+  size_t shadow_len;
+  int i;
+
+  sanitizer_unpoison__ (&shadow_ptr, &shadow_len, ptr, len);
+
+  /* save the shadow area */
+  for (i = 0; i < shadow_len; i++)
+    shadow[i] = shadow_ptr[i];
+
+  /* unpoison */
+  for (i = 0; i < shadow_len; i++)
+    shadow_ptr[i] = 0;
+}
+
+static_always_inline CLIB_NOSANITIZE_ADDR void
+sanitizer_unpoison_pop__ (const u64 *restrict shadow, const void *ptr,
+			  size_t len)
+{
+  u64 *restrict shadow_ptr;
+  size_t shadow_len;
+  int i;
+
+  sanitizer_unpoison__ (&shadow_ptr, &shadow_len, ptr, len);
+
+  /* restore the shadow area */
+  for (i = 0; i < shadow_len; i++)
+    {
+      ASSERT (0 == shadow_ptr[i]);
+      shadow_ptr[i] = shadow[i];
+    }
+}
+
+#define CLIB_MEM_OVERFLOW(f, src, n)                                          \
+  ({                                                                          \
+    typeof (f) clib_mem_overflow_ret__;                                       \
+    const void *clib_mem_overflow_src__ = (src);                              \
+    size_t clib_mem_overflow_n__ = (n);                                       \
+    u64 clib_mem_overflow_shadow__[CLIB_MEM_OVERFLOW_MAX];                    \
+    sanitizer_unpoison_push__ (clib_mem_overflow_shadow__,                    \
+			       clib_mem_overflow_src__,                       \
+			       clib_mem_overflow_n__);                        \
+    clib_mem_overflow_ret__ = f;                                              \
+    sanitizer_unpoison_pop__ (clib_mem_overflow_shadow__,                     \
+			      clib_mem_overflow_src__,                        \
+			      clib_mem_overflow_n__);                         \
+    clib_mem_overflow_ret__;                                                  \
+  })
 
 #define CLIB_MEM_OVERFLOW_LOAD(f, src) \
   ({ \