bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K

[mirror_ubuntu-bionic-kernel.git] / kernel / bpf / core.c

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 72ca4040daa33e0c4a939065bb150b8f65c3b68e..4a843430d44c49549ade3d63d5deb11c10872fc3 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -290,13 +290,11 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 }
 
 #ifdef CONFIG_BPF_JIT
-# define BPF_JIT_LIMIT_DEFAULT (PAGE_SIZE * 40000)
-
 /* All BPF JIT sysctl knobs here. */
 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;
-int bpf_jit_limit    __read_mostly = BPF_JIT_LIMIT_DEFAULT;
+long bpf_jit_limit   __read_mostly;
 
 static __always_inline void
 bpf_get_prog_addr_region(const struct bpf_prog *prog,
@@ -507,16 +505,27 @@ int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 
 static atomic_long_t bpf_jit_current;
 
+/* Can be overridden by an arch's JIT compiler if it has a custom,
+ * dedicated BPF backend memory area, or if neither of the two
+ * below apply.
+ */
+u64 __weak bpf_jit_alloc_exec_limit(void)
+{
 #if defined(MODULES_VADDR)
+       return MODULES_END - MODULES_VADDR;
+#else
+       return VMALLOC_END - VMALLOC_START;
+#endif
+}
+
 static int __init bpf_jit_charge_init(void)
 {
        /* Only used as heuristic here to derive limit. */
-       bpf_jit_limit = min_t(u64, round_up((MODULES_END - MODULES_VADDR) >> 2,
-                                           PAGE_SIZE), INT_MAX);
+       bpf_jit_limit = min_t(u64, round_up(bpf_jit_alloc_exec_limit() >> 2,
+                                           PAGE_SIZE), LONG_MAX);
        return 0;
 }
 pure_initcall(bpf_jit_charge_init);
-#endif
 
 static int bpf_jit_charge_modmem(u32 pages)
 {