From: matoro <matoro_mailinglist_kernel@matoro.tk>
To: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Eric Biederman <ebiederm@xmission.com>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
stable@vger.kernel.org,
Thorsten Leemhuis <regressions@leemhuis.info>,
Anthony Yznaga <anthony.yznaga@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
regressions@lists.linux.dev, linux-ia64@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] binfmt_elf: Avoid total_mapping_size for ET_EXEC
Date: Mon, 28 Feb 2022 15:31:00 -0500 [thread overview]
Message-ID: <5d44f028b2d739395c92e4b3036e2bbf@matoro.tk> (raw)
In-Reply-To: <20220228194613.1149432-1-keescook@chromium.org>
On 2022-02-28 14:46, 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@zeniv.linux.org.uk>
> Cc: Eric Biederman <ebiederm@xmission.com>
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-mm@kvack.org
> Reported-by: matoro <matoro_mailinglist_kernel@matoro.tk>
> Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
> Fixes: 5f501d555653 ("binfmt_elf: reintroduce using
> MAP_FIXED_NOREPLACE")
> Link:
> https://lore.kernel.org/r/a3edd529-c42d-3b09-135c-7e98a15b150f@leemhuis.info
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> matoro (or anyone else) can you please test this?
> ---
> 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 9bea703ed1c2..474b44032c65 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1136,14 +1136,25 @@ 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 first_pt_load is set to false later once the
> - * initial mapping is performed.)
> - */
> - if (first_pt_load) {
> + /*
> + * 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) {
This does not apply for me, I'm looking around and can't find any
reference to the first_pt_load variable you're removing there? What
commit/tag are you applying this on top of?
next prev parent reply other threads:[~2022-02-28 20:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-28 19:46 [PATCH] binfmt_elf: Avoid total_mapping_size for ET_EXEC Kees Cook
2022-02-28 20:31 ` matoro [this message]
2022-02-28 20:46 ` Kees Cook
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