[PATCH] fs/binfmt_elf: fix PT_LOAD p_align values for loaders

[PATCH] fs/binfmt_elf: fix PT_LOAD p_align values for loaders

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

Rui Salvaterra reported that Aisleroit solitaire crashes with "Wrong
__data_start/_end pair" assertion from libgc after update to v5.17-rc1.

Bisection pointed to commit 9630f0d60fec ("fs/binfmt_elf: use PT_LOAD
p_align values for static PIE") that fixed handling of static PIEs, but
made the condition that guards load_bias calculation to exclude loader
binaries.

Restoring the check for presence of interpreter fixes the problem.

Fixes: 9630f0d60fec ("fs/binfmt_elf: use PT_LOAD p_align values for static PIE")
Reported-by: Rui Salvaterra <rsalvaterra@gmail.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
 fs/binfmt_elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 605017eb9349..9e11e6f13e83 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1117,7 +1117,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 			 * without MAP_FIXED nor MAP_FIXED_NOREPLACE).
 			 */
 			alignment = maximum_alignment(elf_phdata, elf_ex->e_phnum);
-			if (alignment > ELF_MIN_ALIGN) {
+			if (interpreter || alignment > ELF_MIN_ALIGN) {
 				load_bias = ELF_ET_DYN_BASE;
 				if (current->flags & PF_RANDOMIZE)
 					load_bias += arch_mmap_rnd();
-- 
2.34.1

Re: [PATCH] fs/binfmt_elf: fix PT_LOAD p_align values for loaders

[Rui Salvaterra]

Hi, Mike,

On Wed, 2 Feb 2022 at 12:14, Mike Rapoport <rppt@kernel.org> wrote:
>
> From: Mike Rapoport <rppt@linux.ibm.com>
>
> Rui Salvaterra reported that Aisleroit solitaire crashes with "Wrong
> __data_start/_end pair" assertion from libgc after update to v5.17-rc1.
>
> Bisection pointed to commit 9630f0d60fec ("fs/binfmt_elf: use PT_LOAD
> p_align values for static PIE") that fixed handling of static PIEs, but
> made the condition that guards load_bias calculation to exclude loader
> binaries.
>
> Restoring the check for presence of interpreter fixes the problem.
>
> Fixes: 9630f0d60fec ("fs/binfmt_elf: use PT_LOAD p_align values for static PIE")
> Reported-by: Rui Salvaterra <rsalvaterra@gmail.com>
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
>  fs/binfmt_elf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 605017eb9349..9e11e6f13e83 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1117,7 +1117,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
>                          * without MAP_FIXED nor MAP_FIXED_NOREPLACE).
>                          */
>                         alignment = maximum_alignment(elf_phdata, elf_ex->e_phnum);
> -                       if (alignment > ELF_MIN_ALIGN) {
> +                       if (interpreter || alignment > ELF_MIN_ALIGN) {
>                                 load_bias = ELF_ET_DYN_BASE;
>                                 if (current->flags & PF_RANDOMIZE)
>                                         load_bias += arch_mmap_rnd();
> --
> 2.34.1
>

The patch does fix the problem for me, and is thus

Tested-by: Rui Salvaterra <rsalvaterra@gmail.com>

Thanks,
Rui