[PATCH] PR32870: ld: arm32: fix segfault when linking with LLVMgold.so plugin under LTO

[dongjianqiang (A)]

Hi Alan and Richard,
Thank you for reviewing this, can you please help install this patch ? I am not a binutils committer.

> -----Original Message-----
> From: Alan Modra [mailto:amodra@gmail.com]
> Sent: Wednesday, June 4, 2025 8:34 AM
> To: Richard Earnshaw <Richard.Earnshaw@arm.com>
> Cc: dongjianqiang (A) <dongjianqiang2@huawei.com>;
> binutils@sourceware.org; Zhangwen(Esan)
> <zwzhangwen.zhang@huawei.com>; Yangjian (Compiler)
> <yangjian86@huawei.com>; sam@gentoo.org
> Subject: Re: [PATCH] PR32870: ld: arm32: fix segfault when linking with
> LLVMgold.so plugin under LTO
> 
> On Tue, Jun 03, 2025 at 04:58:36PM +0100, Richard Earnshaw wrote:
> > On 15/04/2025 10:14, dongjianqiang (A) wrote:
> > > Hi,
> > >
> > > Proposed patch to PR32870.
> > > When handling the iplt in ARM32, the ld must check whether the
> input_bfd
> > > is in ELF format. If the input is an LLVM Bitcode file, an error will be raised.
> > >
> > > Any suggestions? Thanks.
> > >
> > > ---
> > > 	PR 32870
> > > 	* elf32-arm.c (elf32_arm_output_arch_local_syms): Check input_bfd
> > >
> > > diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
> > > index 3b7cee3de1c..3af964ce034 100644
> > > --- a/bfd/elf32-arm.c
> > > +++ b/bfd/elf32-arm.c
> > > @@ -18345,6 +18345,9 @@ elf32_arm_output_arch_local_syms (bfd
> *output_bfd,
> > >   	  struct arm_local_iplt_info **local_iplt;
> > >   	  unsigned int i, num_syms;
> > > +	  if (!is_arm_elf (input_bfd))
> > > +	    continue;
> > > +
> > >   	  local_iplt = elf32_arm_local_iplt (input_bfd);
> > >   	  if (local_iplt != NULL)
> > >   	    {
> >
> > I'd like Alan's opinion on this one.  To me it's strange that something that
> > is not remotely like a object file is still in the list of input BFDs at
> > this point.  This feels like it might be yet another rich source of fuzzing
> > bugs.
> 
> The patch is OK.
> 
> GNU ld can link foreign object files, if they have no relocations or
> the relocs are simple enough and the target support for that object
> properly describes them in reloc howtos.
> 
> > If keeping this in the bfd list is correct, then I think a better fix would
> > be to refuse to create a local iplt for this bfd; then we'll simply skip the
> > following code because elf32_arm_local_iplt will simply return NULL.
> 
> Well, as things stand you need to check the input bfd is the correct
> type and thus has elf_arm_obj_tdata before even accessing
> elf32_arm_local_iplt.
> 
> --
> Alan Modra