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Miller" , Thomas Garnier , kernel-team@fb.com, Steven Rostedt , Ingo Molnar , Josef Bacik , Alexei Starovoitov , netdev@vger.kernel.org Subject: Re: [PATCH] bpf: whitelist syscalls for error injection Message-ID: <20180313234509.GA4981@vader> References: <20180313231627.1247-1-hmclauchlan@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180313231627.1247-1-hmclauchlan@fb.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Tue, Mar 13, 2018 at 04:16:27PM -0700, Howard McLauchlan wrote: > Error injection is a useful mechanism to fail arbitrary kernel > functions. 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, -ENOENT); > return 0; > } > """ % pid > > b = BPF(text = prog) > while 1: > b.perf_buffer_poll() > > This patch whitelists all syscalls defined with SYSCALL_DEFINE for error > injection. > > Signed-off-by: Howard McLauchlan > --- > based on 4.16-rc5 > include/linux/syscalls.h | 3 +++ > 1 file changed, 3 insertions(+) > > 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 > Adding a few more people to Cc