[COMMITTED][Bug libdw/30980] dwfl_offline_section_address: replace asserts with early return

[COMMITTED][Bug libdw/30980] dwfl_offline_section_address: replace asserts with early return

[Aaron Merey]

dwfl_offline_section_address asserts that the current module is ET_REL.

A possibly corrupt .gnu_debuglink can cause an abort by calling
dwfl_offline_section_address on an ET_DYN module.

Prevent this abort and similar ones by replacing
dwfl_offline_section_address initial asserts with an early return.

https://sourceware.org/bugzilla/show_bug.cgi?id=30980

Signed-off-by: Aaron Merey <amerey@redhat.com>

---
 libdwfl/offline.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/libdwfl/offline.c b/libdwfl/offline.c
index e090b42b..52539fe3 100644
--- a/libdwfl/offline.c
+++ b/libdwfl/offline.c
@@ -50,10 +50,11 @@ dwfl_offline_section_address (Dwfl_Module *mod,
 			      const GElf_Shdr *shdr __attribute__ ((unused)),
 			      Dwarf_Addr *addr)
 {
-  assert (mod->e_type == ET_REL);
-  assert (shdr->sh_addr == 0);
-  assert (shdr->sh_flags & SHF_ALLOC);
-  assert (shndx != 0);
+  if (mod->e_type != ET_REL
+      || shdr->sh_addr != 0
+      || !(shdr->sh_flags & SHF_ALLOC)
+      || shndx == 0)
+    return -1;
 
   if (mod->debug.elf == NULL)
     /* We are only here because sh_addr is zero even though layout is complete.
-- 
2.41.0