From: Kees Cook <keescook@chromium.org>
To: YiFei Zhu <zhuyifei1999@gmail.com>
Cc: containers@lists.linux-foundation.org,
YiFei Zhu <yifeifz2@illinois.edu>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Aleksa Sarai <cyphar@cyphar.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andy Lutomirski <luto@amacapital.net>,
David Laight <David.Laight@aculab.com>,
Dimitrios Skarlatos <dskarlat@cs.cmu.edu>,
Giuseppe Scrivano <gscrivan@redhat.com>,
Hubertus Franke <frankeh@us.ibm.com>,
Jack Chen <jianyan2@illinois.edu>, Jann Horn <jannh@google.com>,
Josep Torrellas <torrella@illinois.edu>,
Tianyin Xu <tyxu@illinois.edu>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
Tycho Andersen <tycho@tycho.pizza>,
Valentin Rothberg <vrothber@redhat.com>,
Will Drewry <wad@chromium.org>
Subject: Re: [PATCH v3 seccomp 3/5] seccomp/cache: Lookup syscall allowlist for fast path
Date: Wed, 30 Sep 2020 14:32:46 -0700 [thread overview]
Message-ID: <202009301422.D9F6E6A@keescook> (raw)
In-Reply-To: <83c72471f9f79fa982508bd4db472686a67b8320.1601478774.git.yifeifz2@illinois.edu>
On Wed, Sep 30, 2020 at 10:19:14AM -0500, YiFei Zhu wrote:
> From: YiFei Zhu <yifeifz2@illinois.edu>
>
> The fast (common) path for seccomp should be that the filter permits
> the syscall to pass through, and failing seccomp is expected to be
> an exceptional case; it is not expected for userspace to call a
> denylisted syscall over and over.
>
> This first finds the current allow bitmask by iterating through
> syscall_arches[] array and comparing it to the one in struct
> seccomp_data; this loop is expected to be unrolled. It then
> does a test_bit against the bitmask. If the bit is set, then
> there is no need to run the full filter; it returns
> SECCOMP_RET_ALLOW immediately.
>
> Co-developed-by: Dimitrios Skarlatos <dskarlat@cs.cmu.edu>
> Signed-off-by: Dimitrios Skarlatos <dskarlat@cs.cmu.edu>
> Signed-off-by: YiFei Zhu <yifeifz2@illinois.edu>
I'd like the content/ordering of this and the emulator patch to be reorganized a bit.
I'd like to see the infrastructure of the cache added first (along with
the "always allow" test logic in this patch), with the emulator missing:
i.e. the patch is a logical no-op: no behavior changes because nothing
ever changes the cache bits, but all the operational logic, structure
changes, etc, is in place. Then the next patch would be replacing the
no-op with the emulator.
> ---
> kernel/seccomp.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 52 insertions(+)
>
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index f09c9e74ae05..bed3b2a7f6c8 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -172,6 +172,12 @@ struct seccomp_cache_filter_data { };
> static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter)
> {
> }
> +
> +static inline bool seccomp_cache_check(const struct seccomp_filter *sfilter,
bikeshedding: "cache check" doesn't tell me anything about what it's
actually checking for. How about calling this seccomp_is_constant_allow() or
something that reflects both the "bool" return ("is") and what that bool
means ("should always be allowed").
> + const struct seccomp_data *sd)
> +{
> + return false;
> +}
> #endif /* CONFIG_SECCOMP_CACHE_NR_ONLY */
>
> /**
> @@ -331,6 +337,49 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
> return 0;
> }
>
> +#ifdef CONFIG_SECCOMP_CACHE_NR_ONLY
> +static bool seccomp_cache_check_bitmap(const void *bitmap, size_t bitmap_size,
Please also mark as "inline".
> + int syscall_nr)
> +{
> + if (unlikely(syscall_nr < 0 || syscall_nr >= bitmap_size))
> + return false;
> + syscall_nr = array_index_nospec(syscall_nr, bitmap_size);
> +
> + return test_bit(syscall_nr, bitmap);
> +}
> +
> +/**
> + * seccomp_cache_check - lookup seccomp cache
> + * @sfilter: The seccomp filter
> + * @sd: The seccomp data to lookup the cache with
> + *
> + * Returns true if the seccomp_data is cached and allowed.
> + */
> +static bool seccomp_cache_check(const struct seccomp_filter *sfilter,
inline too.
> + const struct seccomp_data *sd)
> +{
> + int syscall_nr = sd->nr;
> + const struct seccomp_cache_filter_data *cache = &sfilter->cache;
> +
> +#ifdef SECCOMP_ARCH_DEFAULT
> + if (likely(sd->arch == SECCOMP_ARCH_DEFAULT))
> + return seccomp_cache_check_bitmap(cache->syscall_allow_default,
> + SECCOMP_ARCH_DEFAULT_NR,
> + syscall_nr);
> +#endif /* SECCOMP_ARCH_DEFAULT */
> +
> +#ifdef SECCOMP_ARCH_COMPAT
> + if (likely(sd->arch == SECCOMP_ARCH_COMPAT))
> + return seccomp_cache_check_bitmap(cache->syscall_allow_compat,
> + SECCOMP_ARCH_COMPAT_NR,
> + syscall_nr);
> +#endif /* SECCOMP_ARCH_COMPAT */
> +
> + WARN_ON_ONCE(true);
> + return false;
> +}
> +#endif /* CONFIG_SECCOMP_CACHE_NR_ONLY */
> +
> /**
> * seccomp_run_filters - evaluates all seccomp filters against @sd
> * @sd: optional seccomp data to be passed to filters
> @@ -353,6 +402,9 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd,
> if (WARN_ON(f == NULL))
> return SECCOMP_RET_KILL_PROCESS;
>
> + if (seccomp_cache_check(f, sd))
> + return SECCOMP_RET_ALLOW;
> +
> /*
> * All filters in the list are evaluated and the lowest BPF return
> * value always takes priority (ignoring the DATA).
> --
> 2.28.0
>
Otherwise, yup, looks good.
--
Kees Cook
next prev parent reply other threads:[~2020-09-30 21:33 UTC|newest]
Thread overview: 149+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 5:35 [RFC PATCH seccomp 0/2] seccomp: Add bitmap cache of arg-independent filter results that allow syscalls YiFei Zhu
2020-09-21 5:35 ` [RFC PATCH seccomp 1/2] seccomp/cache: Add "emulator" to check if filter is arg-dependent YiFei Zhu
2020-09-21 17:47 ` Jann Horn
2020-09-21 18:38 ` Jann Horn
2020-09-21 23:44 ` YiFei Zhu
2020-09-22 0:25 ` Jann Horn
2020-09-22 0:47 ` YiFei Zhu
2020-09-21 5:35 ` [RFC PATCH seccomp 2/2] seccomp/cache: Cache filter results that allow syscalls YiFei Zhu
2020-09-21 18:08 ` Jann Horn
2020-09-21 22:50 ` YiFei Zhu
2020-09-21 22:57 ` Jann Horn
2020-09-21 23:08 ` YiFei Zhu
2020-09-25 0:01 ` [PATCH v2 seccomp 2/6] asm/syscall.h: Add syscall_arches[] array Kees Cook
2020-09-25 0:15 ` Jann Horn
2020-09-25 0:18 ` Al Viro
2020-09-25 0:24 ` Jann Horn
2020-09-25 1:27 ` YiFei Zhu
2020-09-25 3:09 ` Kees Cook
2020-09-25 3:28 ` YiFei Zhu
2020-09-25 16:39 ` YiFei Zhu
2020-09-21 5:48 ` [RFC PATCH seccomp 0/2] seccomp: Add bitmap cache of arg-independent filter results that allow syscalls Sargun Dhillon
2020-09-21 7:13 ` YiFei Zhu
2020-09-21 8:30 ` Christian Brauner
2020-09-21 8:44 ` YiFei Zhu
2020-09-21 13:51 ` Tycho Andersen
2020-09-21 15:27 ` YiFei Zhu
2020-09-21 16:39 ` Tycho Andersen
2020-09-21 22:57 ` YiFei Zhu
2020-09-21 19:16 ` Jann Horn
[not found] ` <OF8837FC1A.5C0D4D64-ON852585EA.006B677F-852585EA.006BA663@notes.na.collabserv.com>
2020-09-21 19:45 ` Jann Horn
2020-09-23 19:26 ` Kees Cook
2020-09-23 22:54 ` YiFei Zhu
2020-09-24 6:52 ` Kees Cook
2020-09-24 12:06 ` [PATCH seccomp 0/6] " YiFei Zhu
2020-09-24 12:06 ` [PATCH seccomp 1/6] seccomp: Move config option SECCOMP to arch/Kconfig YiFei Zhu
2020-09-24 12:06 ` YiFei Zhu
2020-09-24 12:06 ` [PATCH seccomp 2/6] asm/syscall.h: Add syscall_arches[] array YiFei Zhu
2020-09-24 12:06 ` [PATCH seccomp 3/6] seccomp/cache: Add "emulator" to check if filter is arg-dependent YiFei Zhu
2020-09-24 12:06 ` [PATCH seccomp 4/6] seccomp/cache: Lookup syscall allowlist for fast path YiFei Zhu
2020-09-24 12:06 ` [PATCH seccomp 5/6] selftests/seccomp: Compare bitmap vs filter overhead YiFei Zhu
2020-09-24 12:06 ` [PATCH seccomp 6/6] seccomp/cache: Report cache data through /proc/pid/seccomp_cache YiFei Zhu
2020-09-24 12:44 ` [PATCH v2 seccomp 0/6] seccomp: Add bitmap cache of arg-independent filter results that allow syscalls YiFei Zhu
2020-09-24 12:44 ` [PATCH v2 seccomp 1/6] seccomp: Move config option SECCOMP to arch/Kconfig YiFei Zhu
2020-09-24 19:11 ` Kees Cook
2020-10-27 9:52 ` Geert Uytterhoeven
2020-10-27 19:08 ` YiFei Zhu
2020-10-28 0:06 ` Kees Cook
2020-10-28 8:18 ` Geert Uytterhoeven
2020-10-28 9:34 ` Jann Horn
2020-09-24 12:44 ` [PATCH v2 seccomp 2/6] asm/syscall.h: Add syscall_arches[] array YiFei Zhu
2020-09-24 13:47 ` David Laight
2020-09-24 14:16 ` YiFei Zhu
2020-09-24 14:20 ` David Laight
2020-09-24 14:37 ` YiFei Zhu
2020-09-24 16:02 ` YiFei Zhu
2020-09-24 12:44 ` [PATCH v2 seccomp 3/6] seccomp/cache: Add "emulator" to check if filter is arg-dependent YiFei Zhu
2020-09-24 23:25 ` Kees Cook
2020-09-25 3:04 ` YiFei Zhu
2020-09-25 16:45 ` YiFei Zhu
2020-09-25 19:42 ` Kees Cook
2020-09-25 19:51 ` Andy Lutomirski
2020-09-25 20:37 ` Kees Cook
2020-09-25 21:07 ` Andy Lutomirski
2020-09-25 23:49 ` Kees Cook
2020-09-26 0:34 ` Andy Lutomirski
2020-09-26 1:23 ` YiFei Zhu
2020-09-26 2:47 ` Andy Lutomirski
2020-09-26 4:35 ` Kees Cook
2020-09-24 12:44 ` [PATCH v2 seccomp 4/6] seccomp/cache: Lookup syscall allowlist for fast path YiFei Zhu
2020-09-24 23:46 ` Kees Cook
2020-09-25 1:55 ` YiFei Zhu
2020-09-24 12:44 ` [PATCH v2 seccomp 5/6] selftests/seccomp: Compare bitmap vs filter overhead YiFei Zhu
2020-09-24 23:47 ` Kees Cook
2020-09-25 1:35 ` YiFei Zhu
2020-09-24 12:44 ` [PATCH v2 seccomp 6/6] seccomp/cache: Report cache data through /proc/pid/seccomp_cache YiFei Zhu
2020-09-24 23:56 ` Kees Cook
2020-09-25 3:11 ` YiFei Zhu
2020-09-25 3:26 ` Kees Cook
2020-09-30 15:19 ` [PATCH v3 seccomp 0/5] seccomp: Add bitmap cache of constant allow filter results YiFei Zhu
2020-09-30 15:19 ` [PATCH v3 seccomp 1/5] x86: Enable seccomp architecture tracking YiFei Zhu
2020-09-30 21:21 ` Kees Cook
2020-09-30 21:33 ` Jann Horn
2020-09-30 22:53 ` Kees Cook
2020-09-30 23:15 ` Jann Horn
2020-09-30 15:19 ` [PATCH v3 seccomp 2/5] seccomp/cache: Add "emulator" to check if filter is constant allow YiFei Zhu
2020-09-30 22:24 ` Jann Horn
2020-09-30 22:49 ` Kees Cook
2020-10-01 11:28 ` YiFei Zhu
2020-10-01 21:08 ` Jann Horn
2020-09-30 22:40 ` Kees Cook
2020-10-01 11:52 ` YiFei Zhu
2020-10-01 21:05 ` Kees Cook
2020-10-02 11:08 ` YiFei Zhu
2020-10-09 4:47 ` YiFei Zhu
2020-10-09 5:41 ` Kees Cook
2020-09-30 15:19 ` [PATCH v3 seccomp 3/5] seccomp/cache: Lookup syscall allowlist for fast path YiFei Zhu
2020-09-30 21:32 ` Kees Cook [this message]
2020-10-09 0:17 ` YiFei Zhu
2020-10-09 5:35 ` Kees Cook
2020-09-30 15:19 ` [PATCH v3 seccomp 4/5] selftests/seccomp: Compare bitmap vs filter overhead YiFei Zhu
2020-09-30 15:19 ` [PATCH v3 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp_cache YiFei Zhu
2020-09-30 22:00 ` Jann Horn
2020-09-30 23:12 ` Kees Cook
2020-10-01 12:06 ` YiFei Zhu
2020-10-01 16:05 ` Jann Horn
2020-10-01 16:18 ` YiFei Zhu
2020-09-30 22:59 ` Kees Cook
2020-09-30 23:08 ` Jann Horn
2020-09-30 23:21 ` Kees Cook
2020-10-09 17:14 ` [PATCH v4 seccomp 0/5] seccomp: Add bitmap cache of constant allow filter results YiFei Zhu
2020-10-09 17:14 ` [PATCH v4 seccomp 1/5] seccomp/cache: Lookup syscall allowlist bitmap for fast path YiFei Zhu
2020-10-09 21:30 ` Jann Horn
2020-10-09 23:18 ` Kees Cook
2020-10-09 17:14 ` [PATCH v4 seccomp 2/5] seccomp/cache: Add "emulator" to check if filter is constant allow YiFei Zhu
2020-10-09 21:30 ` Jann Horn
2020-10-09 22:47 ` Kees Cook
2020-10-09 17:14 ` [PATCH v4 seccomp 3/5] x86: Enable seccomp architecture tracking YiFei Zhu
2020-10-09 17:25 ` Andy Lutomirski
2020-10-09 18:32 ` YiFei Zhu
2020-10-09 20:59 ` Andy Lutomirski
2020-10-09 17:14 ` [PATCH v4 seccomp 4/5] selftests/seccomp: Compare bitmap vs filter overhead YiFei Zhu
2020-10-09 17:14 ` [PATCH v4 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp_cache YiFei Zhu
2020-10-09 21:45 ` Jann Horn
2020-10-09 23:14 ` Kees Cook
2020-10-10 13:26 ` YiFei Zhu
2020-10-12 22:57 ` Kees Cook
2020-10-13 0:31 ` YiFei Zhu
2020-10-22 20:52 ` YiFei Zhu
2020-10-22 22:32 ` Kees Cook
2020-10-22 23:40 ` YiFei Zhu
2020-10-24 2:51 ` Kees Cook
2020-10-30 12:18 ` YiFei Zhu
2020-11-03 13:00 ` YiFei Zhu
2020-11-04 0:29 ` Kees Cook
2020-11-04 11:40 ` YiFei Zhu
2020-11-04 18:57 ` Kees Cook
2020-10-11 15:47 ` [PATCH v5 seccomp 0/5]seccomp: Add bitmap cache of constant allow filter results YiFei Zhu
2020-10-11 15:47 ` [PATCH v5 seccomp 1/5] seccomp/cache: Lookup syscall allowlist bitmap for fast path YiFei Zhu
2020-10-12 6:42 ` Jann Horn
2020-10-11 15:47 ` [PATCH v5 seccomp 2/5] seccomp/cache: Add "emulator" to check if filter is constant allow YiFei Zhu
2020-10-12 6:46 ` Jann Horn
2020-10-11 15:47 ` [PATCH v5 seccomp 3/5] x86: Enable seccomp architecture tracking YiFei Zhu
2020-10-11 15:47 ` [PATCH v5 seccomp 4/5] selftests/seccomp: Compare bitmap vs filter overhead YiFei Zhu
2020-10-11 15:47 ` [PATCH v5 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp_cache YiFei Zhu
2020-10-12 6:49 ` Jann Horn
2020-12-17 12:14 ` Geert Uytterhoeven
2020-12-17 18:34 ` YiFei Zhu
2020-12-18 12:35 ` Geert Uytterhoeven
2020-10-27 19:14 ` [PATCH v5 seccomp 0/5]seccomp: Add bitmap cache of constant allow filter results Kees Cook
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