Hello!
On 2/28/22 21:55, Kees Cook wrote:
> Partially revert commit 5f501d555653 ("binfmt_elf: reintroduce using
> MAP_FIXED_NOREPLACE").
>
> At least ia64 has ET_EXEC PT_LOAD segments that are not virtual-address
> contiguous (but _are_ file-offset contiguous). This would result in
> giant mapping attempts to cover the entire span, including the virtual
> address range hole. Disable total_mapping_size for ET_EXEC, which
> reduces the MAP_FIXED_NOREPLACE coverage to only the first PT_LOAD:
>
> $ readelf -lW /usr/bin/gcc
> ...
> Program Headers:
> Type Offset VirtAddr PhysAddr FileSiz MemSiz ...
> ...
> LOAD 0x000000 0x4000000000000000 0x4000000000000000 0x00b5a0 0x00b5a0 ...
> LOAD 0x00b5a0 0x600000000000b5a0 0x600000000000b5a0 0x0005ac 0x000710 ...
> ...
> ^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^^^^^^^ ^^^^^^^^
>
> File offset range : 0x000000-0x00bb4c
> 0x00bb4c bytes
>
> Virtual address range : 0x4000000000000000-0x600000000000bcb0
> 0x200000000000bcb0 bytes
>
> Ironically, this is the reverse of the problem that originally caused
> problems with ET_EXEC and MAP_FIXED_NOREPLACE: overlaps. This problem is
> with holes. Future work could restore full coverage if load_elf_binary()
> were to perform mappings in a separate phase from the loading (where
> it could resolve both overlaps and holes).
>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Reported-by: matoro <matoro_mailinglist_kernel@xxxxxxxxx>
> Reported-by: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
> Fixes: 5f501d555653 ("binfmt_elf: reintroduce using MAP_FIXED_NOREPLACE")
> Link: https://lore.kernel.org/r/a3edd529-c42d-3b09-135c-7e98a15b150f@xxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> Here's the v5.16 backport.
> ---
> fs/binfmt_elf.c | 25 ++++++++++++++++++-------
> 1 file changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index f8c7f26f1fbb..911a9e7044f4 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1135,14 +1135,25 @@ static int load_elf_binary(struct linux_binprm *bprm)
> * is then page aligned.
> */
> load_bias = ELF_PAGESTART(load_bias - vaddr);
> - }
>
> - /*
> - * Calculate the entire size of the ELF mapping (total_size).
> - * (Note that load_addr_set is set to true later once the
> - * initial mapping is performed.)
> - */
> - if (!load_addr_set) {
> + /*
> + * Calculate the entire size of the ELF mapping
> + * (total_size), used for the initial mapping,
> + * due to first_pt_load which is set to false later
> + * once the initial mapping is performed.
> + *
> + * Note that this is only sensible when the LOAD
> + * segments are contiguous (or overlapping). If
> + * used for LOADs that are far apart, this would
> + * cause the holes between LOADs to be mapped,
> + * running the risk of having the mapping fail,
> + * as it would be larger than the ELF file itself.
> + *
> + * As a result, only ET_DYN does this, since
> + * some ET_EXEC (e.g. ia64) may have virtual
> + * memory holes between LOADs.
> + *
> + */
> total_size = total_mapping_size(elf_phdata,
> elf_ex->e_phnum);
> if (!total_size) {
I can confirm that this patch fixes the issue for me.
Tested-By: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
Thanks,
Adrian
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer - glaubitz@xxxxxxxxxx
`. `' Freie Universitaet Berlin - glaubitz@xxxxxxxxxxxxxxxxxxx
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
