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Date: Fri, 6 Jan 2017 13:34:10 -0800
From: Kees Cook <keescook@...omium.org>
To: James Morris <james.l.morris@...cle.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
linux-security-module <linux-security-module@...r.kernel.org>,
Mathias Svensson <idolf@...gle.com>,
Stephen Röttger <sroettger@...gle.com>,
Will Drewry <drewry@...gle.com>
Subject: Re: [PATCH] samples/seccomp: fix 64-bit comparison macros
On Fri, Jan 6, 2017 at 1:32 PM, Kees Cook <keescook@...omium.org> wrote:
> There were some bugs in the JNE64 and JLT64 comparision macros. This fixes
> them, improves comments, and cleans up the file while we are at it.
>
> Reported-by: Stephen Röttger <sroettger@...gle.com>
> Signed-off-by: Mathias Svensson <idolf@...gle.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Cc: stable@...r.kernel.org
Oops, the in-body "From:" got stripped. This patch is authored by Mathias:
From: Mathias Svensson <idolf@...gle.com>
-Kees
> ---
> James, can you apply this to your -next tree please?
> ---
> samples/seccomp/bpf-helper.h | 125 +++++++++++++++++++++++++------------------
> 1 file changed, 72 insertions(+), 53 deletions(-)
>
> diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h
> index 38ee70f3cd5b..1d8de9edd858 100644
> --- a/samples/seccomp/bpf-helper.h
> +++ b/samples/seccomp/bpf-helper.h
> @@ -138,7 +138,7 @@ union arg64 {
> #define ARG_32(idx) \
> BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx))
>
> -/* Loads hi into A and lo in X */
> +/* Loads lo into M[0] and hi into M[1] and A */
> #define ARG_64(idx) \
> BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \
> BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \
> @@ -153,88 +153,107 @@ union arg64 {
> BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \
> jt
>
> -/* Checks the lo, then swaps to check the hi. A=lo,X=hi */
> +#define JA32(value, jt) \
> + BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
> + jt
> +
> +#define JGE32(value, jt) \
> + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
> + jt
> +
> +#define JGT32(value, jt) \
> + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
> + jt
> +
> +#define JLE32(value, jt) \
> + BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
> + jt
> +
> +#define JLT32(value, jt) \
> + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
> + jt
> +
> +/*
> + * All the JXX64 checks assume lo is saved in M[0] and hi is saved in both
> + * A and M[1]. This invariant is kept by restoring A if necessary.
> + */
> #define JEQ64(lo, hi, jt) \
> + /* if (hi != arg.hi) goto NOMATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
> BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
> + /* if (lo != arg.lo) goto NOMATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \
> - BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 1), \
> jt, \
> - BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
> + BPF_STMT(BPF_LD+BPF_MEM, 1)
>
> #define JNE64(lo, hi, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \
> - BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
> + /* if (hi != arg.hi) goto MATCH; */ \
> + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
> + BPF_STMT(BPF_LD+BPF_MEM, 0), \
> + /* if (lo != arg.lo) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \
> - BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 1), \
> jt, \
> - BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
> -
> -#define JA32(value, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
> - jt
> + BPF_STMT(BPF_LD+BPF_MEM, 1)
>
> #define JA64(lo, hi, jt) \
> + /* if (hi & arg.hi) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \
> - BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 0), \
> + /* if (lo & arg.lo) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \
> - BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 1), \
> jt, \
> - BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
> + BPF_STMT(BPF_LD+BPF_MEM, 1)
>
> -#define JGE32(value, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
> - jt
> -
> -#define JLT32(value, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
> - jt
> -
> -/* Shortcut checking if hi > arg.hi. */
> #define JGE64(lo, hi, jt) \
> + /* if (hi > arg.hi) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
> + /* if (hi != arg.hi) goto NOMATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
> - BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 0), \
> + /* if (lo >= arg.lo) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \
> - BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
> - jt, \
> - BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
> -
> -#define JLT64(lo, hi, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
> - BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
> - BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
> - BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
> - BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 1), \
> jt, \
> - BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
> + BPF_STMT(BPF_LD+BPF_MEM, 1)
>
> -#define JGT32(value, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
> - jt
> -
> -#define JLE32(value, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
> - jt
> -
> -/* Check hi > args.hi first, then do the GE checking */
> #define JGT64(lo, hi, jt) \
> + /* if (hi > arg.hi) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
> + /* if (hi != arg.hi) goto NOMATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
> - BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 0), \
> + /* if (lo > arg.lo) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \
> - BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 1), \
> jt, \
> - BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
> + BPF_STMT(BPF_LD+BPF_MEM, 1)
>
> #define JLE64(lo, hi, jt) \
> - BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \
> - BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
> - BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
> + /* if (hi < arg.hi) goto MATCH; */ \
> + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
> + /* if (hi != arg.hi) goto NOMATCH; */ \
> + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
> + BPF_STMT(BPF_LD+BPF_MEM, 0), \
> + /* if (lo <= arg.lo) goto MATCH; */ \
> BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
> - BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
> + BPF_STMT(BPF_LD+BPF_MEM, 1), \
> + jt, \
> + BPF_STMT(BPF_LD+BPF_MEM, 1)
> +
> +#define JLT64(lo, hi, jt) \
> + /* if (hi < arg.hi) goto MATCH; */ \
> + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
> + /* if (hi != arg.hi) goto NOMATCH; */ \
> + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
> + BPF_STMT(BPF_LD+BPF_MEM, 0), \
> + /* if (lo < arg.lo) goto MATCH; */ \
> + BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 2, 0), \
> + BPF_STMT(BPF_LD+BPF_MEM, 1), \
> jt, \
> - BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
> + BPF_STMT(BPF_LD+BPF_MEM, 1)
>
> #define LOAD_SYSCALL_NR \
> BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
> --
> 2.7.4
>
>
> --
> Kees Cook
> Nexus Security
--
Kees Cook
Nexus Security
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