libdwfl: Make sure there is at least one dynamic entry

The buffer read in needs to contain room for at least one Elf32_Dyn or
Elf64_Dyn entry.

Signed-off-by: Mark Wielaard <mark@klomp.org>

2 files changed, 10 insertions, 0 deletions

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index f849b816..d4eee639 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2021-12-16  Mark Wielaard  <mark@klomp.org>
+
+        * link_map.c (dwfl_link_map_report): Make sure dyn_filesz / entsize is
+        non-zero.
+
 2021-12-08  Mark Wielaard  <mark@klomp.org>
 
         * dwfl_segment_report_module.c (dwfl_segment_report_module): Add
diff --git a/libdwfl/link_map.c b/libdwfl/link_map.c
index 82df7b69..177ad9a5 100644
--- a/libdwfl/link_map.c
+++ b/libdwfl/link_map.c
@@ -1017,6 +1017,11 @@ dwfl_link_map_report (Dwfl *dwfl, const void *auxv, size_t auxv_size,
                  in.d_size. The data might have been truncated.  */
               if (dyn_filesz > in.d_size)
                 dyn_filesz = in.d_size;
+              if (dyn_filesz / entsize == 0)
+                {
+                  __libdwfl_seterrno (DWFL_E_BADELF);
+                  return false;
+                }
               void *buf = malloc (dyn_filesz);
               Elf32_Dyn (*d32)[dyn_filesz / sizeof (Elf32_Dyn)] = buf;
               Elf64_Dyn (*d64)[dyn_filesz / sizeof (Elf64_Dyn)] = buf;