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SubjectRe: ppc elf_map breakage with MAP_FIXED_NOREPLACE
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On 02/01/2018 07:18 PM, Michal Hocko wrote:
> On Thu 01-02-18 08:43:34, Anshuman Khandual wrote:
> [...]
>> $dmesg | grep elf_brk
>> [ 9.571192] elf_brk 10030328 elf_bss 10030000
>>
>> static int load_elf_binary(struct linux_binprm *bprm)
>> ---------------------
>>
>> if (unlikely (elf_brk > elf_bss)) {
>> unsigned long nbyte;
>>
>> /* There was a PT_LOAD segment with p_memsz > p_filesz
>> before this one. Map anonymous pages, if needed,
>> and clear the area. */
>> retval = set_brk(elf_bss + load_bias,
>> elf_brk + load_bias,
>> bss_prot);
>>
>>
>> ---------------------
>
> Just a blind shot... Does the following make any difference?
> ---
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 021fe78998ea..04b24d00c911 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -895,7 +895,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> the correct location in memory. */
> for(i = 0, elf_ppnt = elf_phdata;
> i < loc->elf_ex.e_phnum; i++, elf_ppnt++) {
> - int elf_prot = 0, elf_flags;
> + int elf_prot = 0, elf_flags, elf_fixed = MAP_FIXED_NOREPLACE;
> unsigned long k, vaddr;
> unsigned long total_size = 0;
>
> @@ -927,6 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> */
> }
> }
> + elf_fixed = MAP_FIXED;
> }
>
> if (elf_ppnt->p_flags & PF_R)
> @@ -944,7 +945,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> * the ET_DYN load_addr calculations, proceed normally.
> */
> if (loc->elf_ex.e_type == ET_EXEC || load_addr_set) {
> - elf_flags |= MAP_FIXED_NOREPLACE;
> + elf_flags |= elf_fixed;
> } else if (loc->elf_ex.e_type == ET_DYN) {
> /*
> * This logic is run once for the first LOAD Program
> @@ -980,7 +981,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> load_bias = ELF_ET_DYN_BASE;
> if (current->flags & PF_RANDOMIZE)
> load_bias += arch_mmap_rnd();
> - elf_flags |= MAP_FIXED_NOREPLACE;
> + elf_flags |= elf_fixed;
> } else
> load_bias = 0;
>
>

Yeah, it does solve the problem on mmotm-2018-01-25-16-20.

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