Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932173Ab2BYDWm (ORCPT ); Fri, 24 Feb 2012 22:22:42 -0500 Received: from mail-gx0-f174.google.com ([209.85.161.174]:55760 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753888Ab2BYDWk (ORCPT ); Fri, 24 Feb 2012 22:22:40 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of wad@chromium.org designates 10.236.200.165 as permitted sender) smtp.mail=wad@chromium.org; dkim=pass header.i=wad@chromium.org MIME-Version: 1.0 From: Will Drewry To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, kernel-hardening@lists.openwall.com, netdev@vger.kernel.org, x86@kernel.org, arnd@arndb.de, davem@davemloft.net, hpa@zytor.com, mingo@redhat.com, oleg@redhat.com, peterz@infradead.org, rdunlap@xenotime.net, mcgrathr@chromium.org, tglx@linutronix.de, luto@mit.edu, eparis@redhat.com, serge.hallyn@canonical.com, djm@mindrot.org, scarybeasts@gmail.com, indan@nul.nu, pmoore@redhat.com, akpm@linux-foundation.org, corbet@lwn.net, eric.dumazet@gmail.com, markus@chromium.org, coreyb@linux.vnet.ibm.com, keescook@chromium.org, Will Drewry Subject: [PATCH v11 01/12] sk_run_filter: add support for custom load_pointer Date: Fri, 24 Feb 2012 21:21:40 -0600 Message-Id: <1330140111-17201-1-git-send-email-wad@chromium.org> X-Mailer: git-send-email 1.7.5.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10974 Lines: 342 This change allows CONFIG_SECCOMP to make use of BPF programs for user-controlled system call filtering (as shown in this patch series). To minimize the impact on existing BPF evaluation, function pointer use must be declared at sk_chk_filter-time. This allows ancillary load instructions to be generated that use the function pointer rather than adding _any_ code to the existing LD_* instruction paths. Crude performance numbers using udpflood -l 10000000 against dummy0. 3 trials just udpflooding, 3 with tcpdump. Averaged then differenced. [v11 #s] * x86 32-bit (Atom N570 @ 1.66 GHz 2 core HT) [stackprot]: (tcpdump) (no bpf) - Without: 88.19s - 70.98s = 17.21s - With: 90.97s - 74.96s = 15.98s - Slowdown per packet: -123 nanoseconds * x86 64-bit (Atom N570 @ 1.66 GHz 2 core HT) [stackprot]: (tcpdump) (no bpf) - Without: 117.80s - 103.99s = 13.80s - With: 116.81s - 101.85s = 14.96s - Slowdown per packet: 116 nanoseconds In this round of benchmarking, the gap seems narrower and I've attempted to take extra steps to ensure a quiescent system (especially given the wild variability I was seeing on 64-bit last time). It's not clear to me if this overhead (on an Atom-class system) is acceptable or not. Irrespective, I had planned to follow on to this patch set updating every in-kernel callsite of sk_run/chk_filter to use bpf_*_filter directly and alleviate the bounce through. I was hoping that could be done independently, however. If it would make sense to do that first or just duplicate the sk_run_filter code in seccomp.c initially, please let me know. v11: - un-inline sk_*_filter to adhere to the existing export symbol use and not break bpf_jit_free (markus@chromium.org) - updated benchmarks v10: - converted length to a u32 on the struct because it is passed in at bpf_run_filter time anyway. (indan@nul.nu) - added a comment about the LD_*_ falling through (joe@perches.com) - more clean up (pointer->load, drop SKB macro, comments) (indan@nul.nu) v9: - n/a v8: - fixed variable positioning and bad cast (eric.dumazet@gmail.com) - no longer passes A as a pointer (inspection of x86 asm shows A is %ebx again; thanks eric.dumazet@gmail.com) - cleaned up switch macros and expanded use (joe@perches.com, indan@nul.nu) - added length fn pointer and handled LD_W_LEN/LDX_W_LEN - moved from a wrapping struct to a typedef for the function pointer. (matches existing function pointer style) - added comprehensive comment above the typedef. - benchmarks v7: - first cut Signed-off-by: Will Drewry --- include/linux/filter.h | 46 +++++++++++++++++++ net/core/filter.c | 117 +++++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 157 insertions(+), 6 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 8eeb205..bdd02f9 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -110,6 +110,9 @@ struct sock_fprog { /* Required for SO_ATTACH_FILTER. */ */ #define BPF_MEMWORDS 16 +/* BPF program (checking) flags */ +#define BPF_CHK_FLAGS_NO_SKB 1 + /* RATIONALE. Negative offsets are invalid in BPF. We use them to reference ancillary data. Unlike introduction new instructions, it does not break @@ -145,6 +148,33 @@ struct sk_filter struct sock_filter insns[0]; }; +/** + * struct bpf_load_fn - callback and data for bpf_run_filter + * This structure is used by bpf_run_filter if bpf_chk_filter + * was invoked with BPF_CHK_FLAGS_NO_SKB. + * + * @load: + * @data: const pointer to the data passed into bpf_run_filter + * @k: offset into @skb's data + * @size: the size of the requested data in bytes: 1, 2, or 4. + * @buffer: If non-NULL, a 32-bit buffer for staging data. + * + * Returns a pointer to the requested data. + * + * This function operates similarly to load_pointer in net/core/filter.c + * except that the pointer to the returned data must already be + * byteswapped as appropriate to the source data and endianness. + * @buffer may be used if the data needs to be staged. + * + * @length: the length of the supplied data for use by the LD*_LEN + * instructions. + */ +struct bpf_load_fn { + void *(*load)(const void *data, int k, unsigned int size, + void *buffer); + u32 length; +}; + static inline unsigned int sk_filter_len(const struct sk_filter *fp) { return fp->len * sizeof(struct sock_filter) + sizeof(*fp); @@ -153,9 +183,15 @@ static inline unsigned int sk_filter_len(const struct sk_filter *fp) extern int sk_filter(struct sock *sk, struct sk_buff *skb); extern unsigned int sk_run_filter(const struct sk_buff *skb, const struct sock_filter *filter); +extern unsigned int bpf_run_filter(const void *data, + const struct sock_filter *filter, + const struct bpf_load_fn *load_fn); extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk); extern int sk_detach_filter(struct sock *sk); + extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen); +extern int bpf_chk_filter(struct sock_filter *filter, unsigned int flen, u32 flags); + #ifdef CONFIG_BPF_JIT extern void bpf_jit_compile(struct sk_filter *fp); @@ -228,6 +264,16 @@ enum { BPF_S_ANC_HATYPE, BPF_S_ANC_RXHASH, BPF_S_ANC_CPU, + /* Used to differentiate SKB data and generic data */ + BPF_S_ANC_LD_W_ABS, + BPF_S_ANC_LD_H_ABS, + BPF_S_ANC_LD_B_ABS, + BPF_S_ANC_LD_W_LEN, + BPF_S_ANC_LD_W_IND, + BPF_S_ANC_LD_H_IND, + BPF_S_ANC_LD_B_IND, + BPF_S_ANC_LDX_W_LEN, + BPF_S_ANC_LDX_B_MSH, }; #endif /* __KERNEL__ */ diff --git a/net/core/filter.c b/net/core/filter.c index 5dea452..fe8d396 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -98,9 +98,10 @@ int sk_filter(struct sock *sk, struct sk_buff *skb) EXPORT_SYMBOL(sk_filter); /** - * sk_run_filter - run a filter on a socket - * @skb: buffer to run the filter on + * bpf_run_filter - run a BPF filter program on @data + * @data: buffer to run the filter on * @fentry: filter to apply + * @load_fn: custom data accessor * * Decode and apply filter instructions to the skb->data. * Return length to keep, 0 for none. @skb is the data we are @@ -109,8 +110,9 @@ EXPORT_SYMBOL(sk_filter); * and last instruction guaranteed to be a RET, we dont need to check * flen. (We used to pass to this function the length of filter) */ -unsigned int sk_run_filter(const struct sk_buff *skb, - const struct sock_filter *fentry) +unsigned int bpf_run_filter(const void *data, + const struct sock_filter *fentry, + const struct bpf_load_fn *load_fn) { void *ptr; u32 A = 0; /* Accumulator */ @@ -118,6 +120,7 @@ unsigned int sk_run_filter(const struct sk_buff *skb, u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */ u32 tmp; int k; + const struct sk_buff *skb = data; /* * Process array of filter instructions. @@ -350,6 +353,55 @@ load_b: A = 0; continue; } + case BPF_S_ANC_LD_W_ABS: + k = K; +load_fn_w: + ptr = load_fn->load(data, k, 4, &tmp); + if (ptr) { + A = *(u32 *)ptr; + continue; + } + return 0; + case BPF_S_ANC_LD_H_ABS: + k = K; +load_fn_h: + ptr = load_fn->load(data, k, 2, &tmp); + if (ptr) { + A = *(u16 *)ptr; + continue; + } + return 0; + case BPF_S_ANC_LD_B_ABS: + k = K; +load_fn_b: + ptr = load_fn->load(data, k, 1, &tmp); + if (ptr) { + A = *(u8 *)ptr; + continue; + } + return 0; + case BPF_S_ANC_LDX_B_MSH: + ptr = load_fn->load(data, K, 1, &tmp); + if (ptr) { + X = (*(u8 *)ptr & 0xf) << 2; + continue; + } + return 0; + case BPF_S_ANC_LD_W_IND: + k = X + K; + goto load_fn_w; + case BPF_S_ANC_LD_H_IND: + k = X + K; + goto load_fn_h; + case BPF_S_ANC_LD_B_IND: + k = X + K; + goto load_fn_b; + case BPF_S_ANC_LD_W_LEN: + A = load_fn->length; + continue; + case BPF_S_ANC_LDX_W_LEN: + X = load_fn->length; + continue; default: WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n", fentry->code, fentry->jt, @@ -360,6 +412,21 @@ load_b: return 0; } +EXPORT_SYMBOL(bpf_run_filter); + +/** + * sk_run_filter - run a filter on a socket + * @skb: buffer to run the filter on + * @fentry: filter to apply + * + * Runs bpf_run_filter with the struct sk_buff-specific data + * accessor behavior. + */ +unsigned int sk_run_filter(const struct sk_buff *skb, + const struct sock_filter *filter) +{ + return bpf_run_filter(skb, filter, NULL); +} EXPORT_SYMBOL(sk_run_filter); /* @@ -423,9 +490,10 @@ error: } /** - * sk_chk_filter - verify socket filter code + * bpf_chk_filter - verify socket filter BPF code * @filter: filter to verify * @flen: length of filter + * @flags: May be BPF_CHK_FLAGS_NO_SKB or 0 * * Check the user's filter code. If we let some ugly * filter code slip through kaboom! The filter must contain @@ -434,9 +502,13 @@ error: * * All jumps are forward as they are not signed. * + * If BPF_CHK_FLAGS_NO_SKB is set in flags, any SKB-specific + * rules become illegal and a bpf_load_fn will be expected by + * bpf_run_filter. + * * Returns 0 if the rule set is legal or -EINVAL if not. */ -int sk_chk_filter(struct sock_filter *filter, unsigned int flen) +int bpf_chk_filter(struct sock_filter *filter, unsigned int flen, u32 flags) { /* * Valid instructions are initialized to non-0. @@ -542,9 +614,36 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen) pc + ftest->jf + 1 >= flen) return -EINVAL; break; +#define MAYBE_USE_LOAD_FN(CODE) \ + if (flags & BPF_CHK_FLAGS_NO_SKB) { \ + code = BPF_S_ANC_##CODE; \ + break; \ + } + case BPF_S_LD_W_LEN: + MAYBE_USE_LOAD_FN(LD_W_LEN); + break; + case BPF_S_LDX_W_LEN: + MAYBE_USE_LOAD_FN(LDX_W_LEN); + break; + case BPF_S_LD_W_IND: + MAYBE_USE_LOAD_FN(LD_W_IND); + break; + case BPF_S_LD_H_IND: + MAYBE_USE_LOAD_FN(LD_H_IND); + break; + case BPF_S_LD_B_IND: + MAYBE_USE_LOAD_FN(LD_B_IND); + break; + case BPF_S_LDX_B_MSH: + MAYBE_USE_LOAD_FN(LDX_B_MSH); + break; case BPF_S_LD_W_ABS: + MAYBE_USE_LOAD_FN(LD_W_ABS); + /* Falls through to BPF_S_LD_B_ABS. */ case BPF_S_LD_H_ABS: + MAYBE_USE_LOAD_FN(LD_H_ABS); case BPF_S_LD_B_ABS: + MAYBE_USE_LOAD_FN(LD_B_ABS); #define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE: \ code = BPF_S_ANC_##CODE; \ break @@ -572,6 +671,12 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen) } return -EINVAL; } +EXPORT_SYMBOL(bpf_chk_filter); + +int sk_chk_filter(struct sock_filter *filter, unsigned int flen) +{ + return bpf_chk_filter(filter, flen, 0); +} EXPORT_SYMBOL(sk_chk_filter); /** -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/