From: Aleksei Vetrov <vvv...@google.com>
__libdw_get_uleb128 and __libdw_get_sleb128 should check if addrp has
already reached the end before unrolling the first step. It is done by
moving __libdw_max_len to the beginning of the function, which already
has all the checks.
Signed-off-by: Aleksei Vetrov <vvv...@google.com>
---
libdw/memory-access.h | 10 ++++++----
tests/leb128.c | 29 ++++++++++++++++++++++++++++-
2 files changed, 34 insertions(+), 5 deletions(-)
diff --git a/libdw/memory-access.h b/libdw/memory-access.h
index fca4129a..1cac6af3 100644
--- a/libdw/memory-access.h
+++ b/libdw/memory-access.h
@@ -72,13 +72,14 @@ __libdw_max_len_sleb128 (const unsigned char *addr, const
unsigned char *end)
static inline uint64_t
__libdw_get_uleb128 (const unsigned char **addrp, const unsigned char *end)
{
+ const size_t max = __libdw_max_len_uleb128 (*addrp, end);
uint64_t acc = 0;
/* Unroll the first step to help the compiler optimize
for the common single-byte case. */
- get_uleb128_step (acc, *addrp, 0);
+ if (likely (max > 0))
+ get_uleb128_step (acc, *addrp, 0);
- const size_t max = __libdw_max_len_uleb128 (*addrp - 1, end);
for (size_t i = 1; i < max; ++i)
get_uleb128_step (acc, *addrp, i);
/* Other implementations set VALUE to UINT_MAX in this
@@ -124,6 +125,7 @@ __libdw_get_uleb128_unchecked (const unsigned char **addrp)
static inline int64_t
__libdw_get_sleb128 (const unsigned char **addrp, const unsigned char *end)
{
+ const size_t max = __libdw_max_len_sleb128 (*addrp, end);
/* Do the work in an unsigned type, but use implementation-defined
behavior to cast to signed on return. This avoids some undefined
behavior when shifting. */
@@ -131,9 +133,9 @@ __libdw_get_sleb128 (const unsigned char **addrp, const
unsigned char *end)
/* Unroll the first step to help the compiler optimize
for the common single-byte case. */
- get_sleb128_step (acc, *addrp, 0);
+ if (likely (max > 0))
+ get_sleb128_step (acc, *addrp, 0);
- const size_t max = __libdw_max_len_sleb128 (*addrp - 1, end);
for (size_t i = 1; i < max; ++i)
get_sleb128_step (acc, *addrp, i);
if (*addrp == end)
diff --git a/tests/leb128.c b/tests/leb128.c
index 47b57c0d..03090d80 100644
--- a/tests/leb128.c
+++ b/tests/leb128.c
@@ -117,6 +117,19 @@ test_sleb (void)
return OK;
}
+static int
+test_sleb_safety (void)
+{
+ const int64_t expected_error = INT64_MAX;
+ int64_t value;
+ const unsigned char *test = NULL;
+ get_sleb128 (value, test, test);
+ if (value != expected_error)
+ return FAIL;
+
+ return OK;
+}
+
static int
test_one_uleb (const unsigned char *data, size_t len, uint64_t expect)
{
@@ -166,8 +179,22 @@ test_uleb (void)
return OK;
}
+static int
+test_uleb_safety (void)
+{
+ const uint64_t expected_error = UINT64_MAX;
+ uint64_t value;
+ const unsigned char *test = NULL;
+ get_uleb128 (value, test, test);
+ if (value != expected_error)
+ return FAIL;
+
+ return OK;
+}
+
int
main (void)
{
- return test_sleb () || test_uleb ();
+ return test_sleb () || test_sleb_safety () || test_uleb ()
+ || test_uleb_safety ();
}
--
2.39.1.405.gd4c25cc71f-goog
