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bpf: restrict access to core bpf sysctls

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Given BPF reaches far beyond just networking these days, it was
never intended to allow setting and in some cases reading those
knobs out of a user namespace root running without CAP_SYS_ADMIN,
thus tighten such access.

Also the bpf_jit_enable = 2 debugging mode should only be allowed
if kptr_restrict is not set since it otherwise can leak addresses
to the kernel log. Dump a note to the kernel log that this is for
debugging JITs only when enabled.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2018-01-20 01:24:34 +01:00 committed by Alexei Starovoitov
parent fa9dd599b4
commit 2e4a30983b
1 changed files with 43 additions and 3 deletions
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46
net/core/sysctl_net_core.c
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@ -251,6 +251,46 @@ static int proc_do_rss_key(struct ctl_table *table, int write,
return proc_dostring(&fake_table, write, buffer, lenp, ppos);
}
#ifdef CONFIG_BPF_JIT
static int proc_dointvec_minmax_bpf_enable(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
int ret, jit_enable = *(int *)table->data;
struct ctl_table tmp = *table;
if (write && !capable(CAP_SYS_ADMIN))
return -EPERM;
tmp.data = &jit_enable;
ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
if (write && !ret) {
if (jit_enable < 2 ||
(jit_enable == 2 && bpf_dump_raw_ok())) {
*(int *)table->data = jit_enable;
if (jit_enable == 2)
pr_warn("bpf_jit_enable = 2 was set! NEVER use this in production, only for JIT debugging!\n");
} else {
ret = -EPERM;
}
}
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,
loff_t *ppos)
{
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
}
# endif
#endif
static struct ctl_table net_core_table[] = {
#ifdef CONFIG_NET
{
@ -326,7 +366,7 @@ static struct ctl_table net_core_table[] = {
.data = &bpf_jit_enable,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.proc_handler = proc_dointvec_minmax_bpf_enable,
# ifdef CONFIG_BPF_JIT_ALWAYS_ON
.extra1 = &one,
.extra2 = &one,
@ -341,7 +381,7 @@ static struct ctl_table net_core_table[] = {
.data = &bpf_jit_harden,
.maxlen = sizeof(int),
.mode = 0600,
.proc_handler = proc_dointvec_minmax,
.proc_handler = proc_dointvec_minmax_bpf_restricted,
.extra1 = &zero,
.extra2 = &two,
},
@ -350,7 +390,7 @@ static struct ctl_table net_core_table[] = {
.data = &bpf_jit_kallsyms,
.maxlen = sizeof(int),
.mode = 0600,
.proc_handler = proc_dointvec_minmax,
.proc_handler = proc_dointvec_minmax_bpf_restricted,
.extra1 = &zero,
.extra2 = &one,
},