bpf/verifier: rework value tracking
Unifies adjusted and unadjusted register value types (e.g. FRAME_POINTER is
now just a PTR_TO_STACK with zero offset).
Tracks value alignment by means of tracking known & unknown bits. This
also replaces the 'reg->imm' (leading zero bits) calculations for (what
were) UNKNOWN_VALUEs.
If pointer leaks are allowed, and adjust_ptr_min_max_vals returns -EACCES,
treat the pointer as an unknown scalar and try again, because we might be
able to conclude something about the result (e.g. pointer & 0x40 is either
0 or 0x40).
Verifier hooks in the netronome/nfp driver were changed to match the new
data structures.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 8e5d31f..85936fa 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -9,6 +9,7 @@
#include <linux/bpf.h> /* for enum bpf_reg_type */
#include <linux/filter.h> /* for MAX_BPF_STACK */
+#include <linux/tnum.h>
/* Just some arbitrary values so we can safely do math without overflowing and
* are obviously wrong for any sort of memory access.
@@ -19,30 +20,37 @@
struct bpf_reg_state {
enum bpf_reg_type type;
union {
- /* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */
- s64 imm;
-
- /* valid when type == PTR_TO_PACKET* */
- struct {
- u16 off;
- u16 range;
- };
+ /* valid when type == PTR_TO_PACKET */
+ u16 range;
/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
* PTR_TO_MAP_VALUE_OR_NULL
*/
struct bpf_map *map_ptr;
};
+ /* Fixed part of pointer offset, pointer types only */
+ s32 off;
+ /* For PTR_TO_PACKET, used to find other pointers with the same variable
+ * offset, so they can share range knowledge.
+ * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
+ * came from, when one is tested for != NULL.
+ */
u32 id;
+ /* These three fields must be last. See states_equal() */
+ /* For scalar types (SCALAR_VALUE), this represents our knowledge of
+ * the actual value.
+ * For pointer types, this represents the variable part of the offset
+ * from the pointed-to object, and is shared with all bpf_reg_states
+ * with the same id as us.
+ */
+ struct tnum var_off;
/* Used to determine if any memory access using this register will
- * result in a bad access. These two fields must be last.
- * See states_equal()
+ * result in a bad access.
+ * These refer to the same value as var_off, not necessarily the actual
+ * contents of the register.
*/
s64 min_value;
u64 max_value;
- u32 min_align;
- u32 aux_off;
- u32 aux_off_align;
bool value_from_signed;
};