[binutils-gdb] ubsan: undefined shift in loongarch_elf_add_sub_reloc_uleb128

[Alan Modra]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=50095e94928f244b8ad0cb93201b05499e25ad6e

commit 50095e94928f244b8ad0cb93201b05499e25ad6e
Author: Alan Modra <amodra@gmail.com>
Date:   Tue May 20 15:22:13 2025 +0930

    ubsan: undefined shift in loongarch_elf_add_sub_reloc_uleb128
    
    An oss-fuzz testcase found:
    runtime error: shift exponent 140 is too large for 32-bit type 'int'
    OK, that's just a completely silly uleb, but we ought to be able to
    handle 64 bits here.
    
            * elfxx-loongarch.c (loongarch_elf_add_sub_reloc_uleb128): Formatting.
            Don't left shift int.  Avoid shifts larger than bits in a bfd_vma.

Diff:
---
 bfd/elfxx-loongarch.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/bfd/elfxx-loongarch.c b/bfd/elfxx-loongarch.c
index 94980229501..182617b38c1 100644
--- a/bfd/elfxx-loongarch.c
+++ b/bfd/elfxx-loongarch.c
@@ -2171,11 +2171,11 @@ loongarch_elf_add_sub_reloc_uleb128 (bfd *abfd,
   if (output_bfd != NULL)
     return bfd_reloc_continue;
 
-  relocation = symbol->value + symbol->section->output_section->vma
-    + symbol->section->output_offset + reloc_entry->addend;
+  relocation = (symbol->value + symbol->section->output_section->vma
+		+ symbol->section->output_offset + reloc_entry->addend);
 
-  bfd_size_type octets = reloc_entry->address
-    * bfd_octets_per_byte (abfd, input_section);
+  bfd_size_type octets = (reloc_entry->address
+			  * bfd_octets_per_byte (abfd, input_section));
   if (!bfd_reloc_offset_in_range (reloc_entry->howto, abfd,
 				  input_section, octets))
     return bfd_reloc_outofrange;
@@ -2195,8 +2195,11 @@ loongarch_elf_add_sub_reloc_uleb128 (bfd *abfd,
       break;
     }
 
-  bfd_vma mask = (1 << (7 * len)) - 1;
-  relocation = relocation & mask;
+  if (7 * len < sizeof (bfd_vma))
+    {
+      bfd_vma mask = ((bfd_vma) 1 << (7 * len)) - 1;
+      relocation = relocation & mask;
+    }
   loongarch_write_unsigned_leb128 (p, len, relocation);
   return bfd_reloc_ok;
 }