Messages in this thread | | | Subject | Re: [PATCH] bpf: whitelist syscalls for error injection | From | Yonghong Song <> | Date | Tue, 13 Mar 2018 16:49:29 -0700 |
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On 3/13/18 4:45 PM, Omar Sandoval wrote: > 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 <hmclauchlan@fb.com> >> --- >> 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)
duplication of asmlinkage in the above?
>> >> #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 >
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