linux-kernel - Re: [PATCH] fs: binfmt_elf: Add two ELF header consistency checks

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Date:	Wed, 20 Nov 2013 22:40:19 -0200
From:	Geyslan Gregório Bem <geyslan@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	kernel-br <kernel-br@...glegroups.com>,
	"Geyslan G. Bem" <geyslan@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"open list:FILESYSTEMS (VFS...)" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] fs: binfmt_elf: Add two ELF header consistency checks

2013/11/20 Geyslan G. Bem <geyslan@...il.com>:
> The member 'e_ehsize' that holds the ELF header size is compared
> with the elfhdr struct size. If not equal, goes out.
> If 'e_phoff' holds 0 the object has no program header table, so
> goes out.
>
> Increasing the binary consistency reduces the use of malformed ones.
>
> Both checks are in accordance with the ELF Specifications.
>
> Signed-off-by: Geyslan G. Bem <geyslan@...il.com>
> ---
>  fs/binfmt_elf.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 571a423..3c08f96 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -603,6 +603,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
>         if (memcmp(loc->elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
>                 goto out;
>
> +       if (loc->elf_ex.e_ehsize != sizeof(struct elfhdr))
> +               goto out;
>         if (loc->elf_ex.e_type != ET_EXEC && loc->elf_ex.e_type != ET_DYN)
>                 goto out;
>         if (!elf_check_arch(&loc->elf_ex))
> @@ -611,6 +613,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
>                 goto out;
>
>         /* Now read in all of the header information */
> +       if (loc->elf_ex.e_phoff == 0)
> +               goto out;
>         if (loc->elf_ex.e_phentsize != sizeof(struct elf_phdr))
>                 goto out;
>         if (loc->elf_ex.e_phnum < 1 ||
> --
> 1.8.4.2
>

PATCH v2 Sent:
[PATCH v2] fs: binfmt_elf: Add ELF header consistency checks

-- 
Regards,

Geyslan G. Bem
hackingbits.com
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