[COMMITTED] readelf: Sanity check verneed and verdef offsets in handle_symtab.

[Mark Wielaard]

We are going through vna_next, vn_next and vd_next in a while loop.
Make sure that all offsets are sane. We don't want things to wrap
around so we go in cycles.

https://sourceware.org/bugzilla/show_bug.cgi?id=27501

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 src/ChangeLog |  5 +++++
 src/readelf.c | 10 +++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/ChangeLog b/src/ChangeLog
index 791015bb..14cd6cac 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2021-03-03  Mark Wielaard  <mark@klomp.org>
+
+	* readelf.c (handle_symtab): Sanity check verneed vna_next,
+	vn_next and verdef vd_next offsets.
+
 2021-03-02  Timm Bäder  <tbaeder@redhat.com>
 
 	* elfcompress.c (process_file): Remove cleanup() function and
diff --git a/src/readelf.c b/src/readelf.c
index 715af3b3..b9740455 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -2554,7 +2554,9 @@ handle_symtab (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
 						 &vernaux_mem);
 		      while (vernaux != NULL
 			     && vernaux->vna_other != *versym
-			     && vernaux->vna_next != 0)
+			     && vernaux->vna_next != 0
+			     && (verneed_data->d_size - vna_offset
+				 >= vernaux->vna_next))
 			{
 			  /* Update the offset.  */
 			  vna_offset += vernaux->vna_next;
@@ -2571,6 +2573,9 @@ handle_symtab (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
 			/* Found it.  */
 			break;
 
+		      if (verneed_data->d_size - vn_offset < verneed->vn_next)
+			break;
+
 		      vn_offset += verneed->vn_next;
 		      verneed = (verneed->vn_next == 0
 				 ? NULL
@@ -2606,6 +2611,9 @@ handle_symtab (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
 			/* Found the definition.  */
 			break;
 
+		      if (verdef_data->d_size - vd_offset < verdef->vd_next)
+			break;
+
 		      vd_offset += verdef->vd_next;
 		      verdef = (verdef->vd_next == 0
 				? NULL
-- 
2.20.1