nm: First call elf_getdata, then allocate memory.

This catches bogus data early before we might try to allocate giant
amounts of memory.

Reported-by: Hanno Böck <[email protected]>
Signed-off-by: Mark Wielaard <[email protected]>

2 files changed, 10 insertions, 6 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 7d5e001b..50223a4f 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2015-06-27  Mark Wielaard  <[email protected]>
+
+	* nm.c (show_symbols): First call elf_getdata, then allocate memory.
+
 2015-06-18  Mark Wielaard  <[email protected]>
 
 	* findtextrel.c (process_file): Free segments after use.
diff --git a/src/nm.c b/src/nm.c
index 73395069..15d9da4a 100644
--- a/src/nm.c
+++ b/src/nm.c
@@ -1200,6 +1200,12 @@ show_symbols (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn, Elf_Scn *xndxscn,
 	}
     }
 
+  /* Get the data of the section.  */
+  Elf_Data *data = elf_getdata (scn, NULL);
+  Elf_Data *xndxdata = elf_getdata (xndxscn, NULL);
+  if (data == NULL || (xndxscn != NULL && xndxdata == NULL))
+    INTERNAL_ERROR (fullname);
+
   /* Allocate the memory.
 
      XXX We can use a dirty trick here.  Since GElf_Sym == Elf64_Sym we
@@ -1211,12 +1217,6 @@ show_symbols (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn, Elf_Scn *xndxscn,
   else
     sym_mem = (GElf_SymX *) xmalloc (nentries * sizeof (GElf_SymX));
 
-  /* Get the data of the section.  */
-  Elf_Data *data = elf_getdata (scn, NULL);
-  Elf_Data *xndxdata = elf_getdata (xndxscn, NULL);
-  if (data == NULL || (xndxscn != NULL && xndxdata == NULL))
-    INTERNAL_ERROR (fullname);
-
   /* Iterate over all symbols.  */
 #ifdef USE_DEMANGLE
   size_t demangle_buffer_len = 0;