Re: [PATCH] bpf: whitelist syscalls for error injection

On 03/13/2018 04:56 PM, Andy Lutomirski wrote:

On Tue, Mar 13, 2018 at 11:16 PM, Howard McLauchlan [off-list ref] wrote:

quoted

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.

Temporary NAK IMO.  Specifically:

quoted

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);              \

sys_xyz() is not just the syscall itself; it's also a helper that's
used for entirely silly reasons by various bits of kernel code for
quite a few syscalls.  Fortunately, Dominik has patches to fix that,
and Linus is even considering pulling them for 4.16.  This patch will
most likely conflict with the final result of Dominik's series.

Can you and Dominik coordinate a bit to get this patch or its
equivalent landed on top of Dominik's work?  It might make sense for
Dominik to just add this patch to his series so it can land with the
rest of it.  Dominik, Ingo, what do you think?

--Andy

Dominik, 

This patch applies cleanly on top of your patch series. Is there anything you'd need from me to get this in on top of your work? 

Howard