bpf: Prevent increasing bpf_jit_limit above max

BugLink: https://bugs.launchpad.net/bugs/1953387
[ Upstream commit fadb7ff1a6c2c565af56b4aacdd086b067eed440 ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index c4f89340f49867ec21f52993c467cc871ee2bf78..440014875acf47cd7578100751b5d34b85fc6eac 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -952,6 +952,7 @@ 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 d9a3d995bd96639b76a49cc6cc2a09b51b01ef65..1238ef9c569df55ad8030671b09e5651cfa2b25d 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -523,6 +523,7 @@ int bpf_jit_enable   __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_ALWAYS_ON);
 int bpf_jit_harden   __read_mostly;
 int bpf_jit_kallsyms __read_mostly;
 long bpf_jit_limit   __read_mostly;
+long bpf_jit_limit_max __read_mostly;
 
 static __always_inline void
 bpf_get_prog_addr_region(const struct bpf_prog *prog,
@@ -759,7 +760,8 @@ 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 669cbe1609d9eff38c8bfea79aadd8654c7dbcd4..48041f50ecfb4f4235aef389a83c146e21451e48 100644 (file)
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -424,7 +424,7 @@ 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
        {