bpf: Prevent increasing bpf_jit_limit above max

Restrict bpf_jit_limit to the maximum supported by the arch's JIT.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211014142554.53120-4-lmb@cloudflare.com

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 4a93c12..ef03ff3 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1051,6 +1051,7 @@ extern int bpf_jit_enable;
 extern int bpf_jit_harden;
 extern int bpf_jit_kallsyms;
 extern long bpf_jit_limit;
+extern long bpf_jit_limit_max;
 
 typedef void (*bpf_jit_fill_hole_t)(void *area, unsigned int size);
 

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index d6b7dfd..c1e7eb3 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -524,6 +524,7 @@ int bpf_jit_enable   __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON);
 int bpf_jit_kallsyms __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON);
 int bpf_jit_harden   __read_mostly;
 long bpf_jit_limit   __read_mostly;
+long bpf_jit_limit_max __read_mostly;
 
 static void
 bpf_prog_ksym_set_addr(struct bpf_prog *prog)
@@ -817,7 +818,8 @@ u64 __weak bpf_jit_alloc_exec_limit(void)
 static int __init bpf_jit_charge_init(void)
 {
        /* Only used as heuristic here to derive limit. */
-       bpf_jit_limit = min_t(u64, round_up(bpf_jit_alloc_exec_limit() >> 2,
+       bpf_jit_limit_max = bpf_jit_alloc_exec_limit();
+       bpf_jit_limit = min_t(u64, round_up(bpf_jit_limit_max >> 2,
                                            PAGE_SIZE), LONG_MAX);
        return 0;
 }

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index c8496c1..5f88526 100644 (file)
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -419,7 +419,7 @@ static struct ctl_table net_core_table[] = {
                .mode           = 0600,
                .proc_handler   = proc_dolongvec_minmax_bpf_restricted,
                .extra1         = &long_one,
-               .extra2         = &long_max,
+               .extra2         = &bpf_jit_limit_max,
        },
 #endif
        {