libdwfl: Make sure dyn_filesz has a sane size

In dwfl_segment_report_module dyn_filesz should be able to hold at
least one Elf_Dyn element, and not be larger than possible.

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

2 files changed, 9 insertions, 0 deletions

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 38e2bdaa..1f83576d 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,6 +1,12 @@
 2021-12-08  Mark Wielaard  <mark@klomp.org>
 
         * dwfl_segment_report_module.c (dwfl_segment_report_module): Make sure
+        that dyn_filesz can contain at least one Elf_Dyn and isn't larger than
+        possible.
+
+2021-12-08  Mark Wielaard  <mark@klomp.org>
+
+        * dwfl_segment_report_module.c (dwfl_segment_report_module): Make sure
         that ph_buffer_size has room for at least one phdr.
 
 2021-12-08  Mark Wielaard  <mark@klomp.org>
diff --git a/libdwfl/dwfl_segment_report_module.c b/libdwfl/dwfl_segment_report_module.c
index 840d6f44..78c70795 100644
--- a/libdwfl/dwfl_segment_report_module.c
+++ b/libdwfl/dwfl_segment_report_module.c
@@ -787,6 +787,9 @@ dwfl_segment_report_module (Dwfl *dwfl, int ndx, const char *name,
       if (dyn_data_size != 0)
         dyn_filesz = dyn_data_size;
 
+      if ((dyn_filesz / dyn_entsize) == 0
+          || dyn_filesz > (SIZE_MAX / dyn_entsize))
+        goto out;
       void *dyns = malloc (dyn_filesz);
       Elf32_Dyn *d32 = dyns;
       Elf64_Dyn *d64 = dyns;