[PATCH 5.4 048/355] bpf: Prevent increasing bpf_jit_limit above max

From: Greg Kroah-Hartman
Date: Mon Nov 15 2021 - 12:17:20 EST


From: Lorenz Bauer <lmb@xxxxxxxxxxxxxx>

[ Upstream commit fadb7ff1a6c2c565af56b4aacdd086b067eed440 ]

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

Signed-off-by: Lorenz Bauer <lmb@xxxxxxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20211014142554.53120-4-lmb@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/linux/filter.h | 1 +
kernel/bpf/core.c | 4 +++-
net/core/sysctl_net_core.c | 2 +-
3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index c4f89340f4986..440014875acf4 100644
--- 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 d9a3d995bd966..1238ef9c569df 100644
--- 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 669cbe1609d9e..48041f50ecfb4 100644
--- 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
{
--
2.33.0