From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754474AbeCVB7i (ORCPT ); Wed, 21 Mar 2018 21:59:38 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:56152 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753789AbeCVB7g (ORCPT ); Wed, 21 Mar 2018 21:59:36 -0400 From: Howard McLauchlan To: Dominik Brodowski CC: , Andy Lutomirski , Ingo Molnar , , Howard McLauchlan Subject: [PATCH v2] bpf: whitelist all syscalls for error injection Date: Wed, 21 Mar 2018 18:59:08 -0700 Message-ID: <20180322015908.30433-1-hmclauchlan@fb.com> X-Mailer: git-send-email 2.14.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [2620:10d:c090:200::6:1eb7] X-ClientProxiedBy: SN4PR0201CA0050.namprd02.prod.outlook.com (2603:10b6:803:20::12) To CY1PR15MB0534.namprd15.prod.outlook.com (2a01:111:e400:59d8::24) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 8105768b-734f-4ef7-0000-08d58f988a95 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(5600026)(4604075)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7153060)(7193020);SRVR:CY1PR15MB0534; 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However, it is often hard to guarantee an error propagates appropriately to user space programs. By injecting into syscalls, we can return arbitrary values to user space directly; this increases flexibility and robustness in testing, allowing us to test user space error paths effectively. The following script, for example, fails calls to sys_open() from a given pid: from bcc import BPF from sys import argv pid = argv[1] prog = r""" int kprobe__SyS_open(struct pt_regs *ctx, const char *pathname, int flags) { u32 pid = bpf_get_current_pid_tgid(); if (pid == %s) bpf_override_return(ctx, -ENOMEM); return 0; } """ % pid b = BPF(text=prog) while 1: b.perf_buffer_poll() This patch whitelists all syscalls defined with SYSCALL_DEFINE and COMPAT_SYSCALL_DEFINE for error injection. These changes are not intended to be considered stable, and would normally be configured off. Signed-off-by: Howard McLauchlan --- Dominik, I've updated the patch to support compat syscalls. Please let me know if there are additional changes to be made. Cheers, V1->V2: added similar mechanism in compat.h, clarify commit Based on 4.16-rc6 include/linux/compat.h | 3 +++ include/linux/syscalls.h | 3 +++ 2 files changed, 6 insertions(+) diff --git a/include/linux/compat.h b/include/linux/compat.h index 16c3027074a2..857ddb1cfedf 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -33,6 +33,8 @@ #endif #define COMPAT_SYSCALL_DEFINE0(name) \ + asmlinkage long compat_sys_##name(void); \ + ALLOW_ERROR_INJECTION(compat_sys_##name, ERRNO); \ asmlinkage long compat_sys_##name(void) #define COMPAT_SYSCALL_DEFINE1(name, ...) \ @@ -51,6 +53,7 @@ #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \ asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\ __attribute__((alias(__stringify(compat_SyS##name)))); \ + ALLOW_ERROR_INJECTION(compat_sys##name, ERRNO); \ static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\ asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__));\ asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\ diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index a78186d826d7..e8c6d63ace78 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -191,6 +191,8 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event) #define SYSCALL_DEFINE0(sname) \ SYSCALL_METADATA(_##sname, 0); \ + asmlinkage long sys_##sname(void); \ + ALLOW_ERROR_INJECTION(sys_##sname, ERRNO); \ asmlinkage long sys_##sname(void) #define SYSCALL_DEFINE1(name, ...) SYSCALL_DEFINEx(1, _##name, __VA_ARGS__) @@ -210,6 +212,7 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event) #define __SYSCALL_DEFINEx(x, name, ...) \ asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \ __attribute__((alias(__stringify(SyS##name)))); \ + ALLOW_ERROR_INJECTION(sys##name, ERRNO); \ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \ asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ -- 2.14.1