PR23806, NULL pointer dereference in merge_strings

[Alan Modra]

PR 23806
* merge.c (_bfd_add_merge_section): Don't attempt to merge
sections with ridiculously large alignments.

diff --git a/bfd/merge.c b/bfd/merge.c
index 5e3bba0982..7de0c886df 100644
--- a/bfd/merge.c
+++ b/bfd/merge.c
@@ -24,6 +24,7 @@
as used in ELF SHF_MERGE. */

#include "sysdep.h"
+#include <limits.h>
#include "bfd.h"
#include "elf-bfd.h"
#include "libbfd.h"
@@ -385,12 +386,18 @@ _bfd_add_merge_section (bfd *abfd, void **psinfo, asection *sec,
return TRUE;
}

- align = sec->alignment_power;
- if ((sec->entsize < (unsigned) 1 << align
+#ifndef CHAR_BIT
+#define CHAR_BIT 8
+#endif
+ if (sec->alignment_power >= sizeof (align) * CHAR_BIT)
+ return TRUE;
+
+ align = 1u << sec->alignment_power;
+ if ((sec->entsize < align
&& ((sec->entsize & (sec->entsize - 1))
|| !(sec->flags & SEC_STRINGS)))
- || (sec->entsize > (unsigned) 1 << align
- && (sec->entsize & (((unsigned) 1 << align) - 1))))
+ || (sec->entsize > align
+ && (sec->entsize & (align - 1))))
{
/* Sanity check. If string character size is smaller than
alignment, then we require character size to be a power