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    SubjectRe: [PATCH] bpf: whitelist syscalls for error injection
    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)
    >
    > #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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