From: "Jose E. Marchesi" <jose.marchesi@oracle.com>
To: Alan Modra via Binutils <binutils@sourceware.org>
Subject: Re: PR28055, segfault in bpf special reloc function
Date: Tue, 06 Jul 2021 09:45:38 +0200 [thread overview]
Message-ID: <87r1gbkhr1.fsf@oracle.com> (raw)
In-Reply-To: <YOL5bvrKQB1L3O7N@squeak.grove.modra.org> (Alan Modra via Binutils's message of "Mon, 5 Jul 2021 21:52:06 +0930")
Hi Alan.
> The testcase in this PR tickled two bugs fixed here. output_bfd is
> NULL when a reloc special_function is called for final linking and
> when called from bfd_generic_get_relocated_section_contents. Clearly
> using output_bfd is wrong as it results in segfaults. Not only that,
> the endianness of the reloc field really should be that of the input.
> The second bug was not checking that the entire reloc field was
> contained in the section contents.
Thanks for fixing this.
> I was going to add the following too, but it looks like this would
> only be dead code since ld -r isn't supported in combination of input
> and output that would see this special_function called.
>
> /* If this is a relocatable link (output_bfd test tells us), just
> call the generic function. */
> if (abfd != output_bfd && output_bfd != NULL)
> return bfd_elf_generic_reloc (abfd, reloc_entry, symbol, data,
> input_section, output_bfd, error_message);
>
>
> PR 28055
> * elf64-bpf.c (bpf_elf_generic_reloc): Use correct bfd for bfd_put
> and bfd_put_32 calls. Correct section limit checks.
>
> diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
> index 28c1543c0b6..243df93ae82 100644
> --- a/bfd/elf64-bpf.c
> +++ b/bfd/elf64-bpf.c
> @@ -589,14 +589,15 @@ elf64_bpf_merge_private_bfd_data (bfd *ibfd, struct bfd_link_info *info)
> }
>
> /* A generic howto special function for installing BPF relocations.
> - This function will be called by the assembler (via bfd_install_relocation).
> + This function will be called by the assembler (via bfd_install_relocation),
> + and by various get_relocated_section_contents functions.
> At link time, bpf_elf_relocate_section will resolve the final relocations.
>
> BPF instructions are always big endian, and this approach avoids problems in
> bfd_install_relocation. */
>
> static bfd_reloc_status_type
> -bpf_elf_generic_reloc (bfd * abfd, arelent *reloc_entry, asymbol *symbol,
> +bpf_elf_generic_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
> void *data, asection *input_section,
> bfd *output_bfd,
> char **error_message ATTRIBUTE_UNUSED)
> @@ -607,7 +608,15 @@ bpf_elf_generic_reloc (bfd * abfd, arelent *reloc_entry, asymbol *symbol,
> bfd_byte *where;
>
> /* Sanity check that the address is in range. */
> - if (reloc_entry->address > bfd_get_section_limit (abfd, input_section))
> + if (reloc_entry->howto->type == R_BPF_INSN_64)
> + {
> + bfd_size_type end = bfd_get_section_limit_octets (abfd, input_section);
> + if (reloc_entry->address > end
> + || end - reloc_entry->address < 16)
> + return bfd_reloc_outofrange;
> + }
> + else if (!bfd_reloc_offset_in_range (reloc_entry->howto, abfd, input_section,
> + reloc_entry->address))
> return bfd_reloc_outofrange;
>
> /* Get the symbol value. */
> @@ -640,15 +649,15 @@ bpf_elf_generic_reloc (bfd * abfd, arelent *reloc_entry, asymbol *symbol,
> instructions, and the upper 32 bits placed at the very end of the
> instruction. that is, there are 32 unused bits between them. */
>
> - bfd_put_32 (output_bfd, (relocation & 0xFFFFFFFF), where + 4);
> - bfd_put_32 (output_bfd, (relocation >> 32), where + 12);
> + bfd_put_32 (abfd, (relocation & 0xFFFFFFFF), where + 4);
> + bfd_put_32 (abfd, (relocation >> 32), where + 12);
> }
> else
> {
> /* For other kinds of relocations, the relocated value simply goes
> BITPOS bits from the start of the entry. This is always a multiple
> of 8, i.e. whole bytes. */
> - bfd_put (reloc_entry->howto->bitsize, output_bfd, relocation,
> + bfd_put (reloc_entry->howto->bitsize, abfd, relocation,
> where + reloc_entry->howto->bitpos / 8);
> }
prev parent reply other threads:[~2021-07-06 7:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-05 12:22 Alan Modra
2021-07-05 14:37 ` Simon Marchi
2021-07-06 1:14 ` Alan Modra
2021-07-06 7:45 ` Jose E. Marchesi [this message]
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