[PATCH] libdw: Add sanity check to store_implicit_value

[Mark Wielaard]

Don't just skip the block length, but check it is equal to the
op->number that we are going to use as length.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdw/ChangeLog           | 4 ++++
 libdw/dwarf_getlocation.c | 5 ++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 631f2f2a..b254d9cd 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,7 @@
+2022-05-09  Mark Wielaard  <mark@klomp.org>
+
+	* dwarf_getlocation.c (store_implicit_value): Check block length.
+
 2022-04-16  Mark Wielaard  <mark@klomp.org>
 
 	* libdwP.h: Remove atomics.h include.
diff --git a/libdw/dwarf_getlocation.c b/libdw/dwarf_getlocation.c
index 5db3cf97..d0d78163 100644
--- a/libdw/dwarf_getlocation.c
+++ b/libdw/dwarf_getlocation.c
@@ -147,7 +147,10 @@ store_implicit_value (Dwarf *dbg, void **cache, Dwarf_Op *op)
 					   sizeof (struct loc_block_s), 1);
   const unsigned char *data = (const unsigned char *) (uintptr_t) op->number2;
   /* Skip the block length.  */
-  __libdw_get_uleb128_unchecked (&data);
+  Dwarf_Word length;
+  get_uleb128_unchecked (length, data);
+  if (length != op->number)
+    return -1;
   block->addr = op;
   block->data = (unsigned char *) data;
   block->length = op->number;
-- 
2.18.4