[PATCH net] net: core: sysctl: fix compiler warning when only cBPF is present

[PATCH net] net: core: sysctl: fix compiler warning when only cBPF is present

[Alexander Lobakin]

proc_dointvec_minmax_bpf_restricted() has been firstly introduced
in commit 2e4a30983b0f ("bpf: restrict access to core bpf sysctls")
under CONFIG_HAVE_EBPF_JIT. Then, this ifdef has been removed in
ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv
allocations"), because a new sysctl, bpf_jit_limit, made use of it.
Finally, this parameter has become long instead of integer with
fdadd04931c2 ("bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K")
and thus, a new proc_dolongvec_minmax_bpf_restricted() has been
added.
With this last change, we got back to that
proc_dointvec_minmax_bpf_restricted() is used only under
CONFIG_HAVE_EBPF_JIT, but the corresponding ifdef has not been
brought back.

So, in configurations like CONFIG_BPF_JIT=y && CONFIG_HAVE_EBPF_JIT=n
since v4.20 we have:

  CC      net/core/sysctl_net_core.o
net/core/sysctl_net_core.c:292:1: warning: ‘proc_dointvec_minmax_bpf_restricted’ defined but not used [-Wunused-function]
  292 | proc_dointvec_minmax_bpf_restricted(struct ctl_table *table, int write,
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Suppress this by guarding it with CONFIG_HAVE_EBPF_JIT again.

Fixes: fdadd04931c2 ("bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K")
Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
---
 net/core/sysctl_net_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index eb29e5adc84d..70211c9edb02 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -288,6 +288,7 @@ static int proc_dointvec_minmax_bpf_enable(struct ctl_table *table, int write,
 	return ret;
 }
 
+#ifdef CONFIG_HAVE_EBPF_JIT
 static int
 proc_dointvec_minmax_bpf_restricted(struct ctl_table *table, int write,
 				    void __user *buffer, size_t *lenp,
@@ -298,6 +299,7 @@ proc_dointvec_minmax_bpf_restricted(struct ctl_table *table, int write,
 
 	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 }
+#endif /* CONFIG_HAVE_EBPF_JIT */
 
 static int
 proc_dolongvec_minmax_bpf_restricted(struct ctl_table *table, int write,
-- 
2.24.1

Re: [PATCH net] net: core: sysctl: fix compiler warning when only cBPF is present

[Daniel Borkmann]

On Wed, Dec 18, 2019 at 12:18:21PM +0300, Alexander Lobakin wrote:
> proc_dointvec_minmax_bpf_restricted() has been firstly introduced
> in commit 2e4a30983b0f ("bpf: restrict access to core bpf sysctls")
> under CONFIG_HAVE_EBPF_JIT. Then, this ifdef has been removed in
> ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv
> allocations"), because a new sysctl, bpf_jit_limit, made use of it.
> Finally, this parameter has become long instead of integer with
> fdadd04931c2 ("bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K")
> and thus, a new proc_dolongvec_minmax_bpf_restricted() has been
> added.
> With this last change, we got back to that
> proc_dointvec_minmax_bpf_restricted() is used only under
> CONFIG_HAVE_EBPF_JIT, but the corresponding ifdef has not been
> brought back.
> 
> So, in configurations like CONFIG_BPF_JIT=y && CONFIG_HAVE_EBPF_JIT=n
> since v4.20 we have:
> 
>   CC      net/core/sysctl_net_core.o
> net/core/sysctl_net_core.c:292:1: warning: ‘proc_dointvec_minmax_bpf_restricted’ defined but not used [-Wunused-function]
>   292 | proc_dointvec_minmax_bpf_restricted(struct ctl_table *table, int write,
>       | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Suppress this by guarding it with CONFIG_HAVE_EBPF_JIT again.
> 
> Fixes: fdadd04931c2 ("bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K")
> Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>

Applied, thanks!