linux/kernel
YiFei Zhu b44123b4a3 bpf: Add cgroup helpers bpf_{get,set}_retval to get/set syscall return value
The helpers continue to use int for retval because all the hooks
are int-returning rather than long-returning. The return value of
bpf_set_retval is int for future-proofing, in case in the future
there may be errors trying to set the retval.

After the previous patch, if a program rejects a syscall by
returning 0, an -EPERM will be generated no matter if the retval
is already set to -err. This patch change it being forced only if
retval is not -err. This is because we want to support, for
example, invoking bpf_set_retval(-EINVAL) and return 0, and have
the syscall return value be -EINVAL not -EPERM.

For BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY, the prior behavior is
that, if the return value is NET_XMIT_DROP, the packet is silently
dropped. We preserve this behavior for backward compatibility
reasons, so even if an errno is set, the errno does not return to
caller. However, setting a non-err to retval cannot propagate so
this is not allowed and we return a -EFAULT in that case.

Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/b4013fd5d16bed0b01977c1fafdeae12e1de61fb.1639619851.git.zhuyifei@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-01-19 12:51:30 -08:00
..
bpf bpf: Add cgroup helpers bpf_{get,set}_retval to get/set syscall return value 2022-01-19 12:51:30 -08:00
cgroup Networking changes for 5.17. 2022-01-10 19:06:09 -08:00
configs
debug
dma
entry
events
futex
gcov
irq irq: remove unused flags argument from __handle_irq_event_percpu() 2022-01-07 00:25:25 +01:00
kcsan
livepatch
locking locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner() 2021-12-18 10:55:51 +01:00
power
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sched - Add a set of thread_info.flags accessors which snapshot it before 2022-01-10 11:34:10 -08:00
time timekeeping: Really make sure wall_to_monotonic isn't positive 2021-12-17 23:06:22 +01:00
trace Networking changes for 5.17. 2022-01-10 19:06:09 -08:00
.gitignore
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workqueue_internal.h