verifier is using the following structure to track the state of registers:
struct reg_state {
enum bpf_reg_type type;
union {
int imm;
struct bpf_map *map_ptr;
};
};
and later on in states_equal() does memcmp(&old->regs[i], &cur->regs[i],..)
to find equivalent states.
Throughout the code of verifier there are assignements to 'imm' and 'map_ptr'
fields and it's not obvious that most of the assignments into 'imm' don't
need to clear extra 4 bytes (like mark_reg_unknown_value() does) to make sure
that memcmp doesn't go over junk left from 'map_ptr' assignment.
Simplify the code by converting 'int' into 'long'
Suggested-by: Daniel Borkmann <dan...@iogearbox.net>
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
---
kernel/bpf/verifier.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2e08f8e9b771..f4ffb2ce034a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -142,7 +142,7 @@ struct reg_state {
enum bpf_reg_type type;
union {
/* valid when type == CONST_IMM | PTR_TO_STACK */
- int imm;
+ long imm;
/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
* PTR_TO_MAP_VALUE_OR_NULL
@@ -260,7 +260,7 @@ static void print_verifier_state(struct verifier_env *env)
continue;
verbose(" R%d=%s", i, reg_type_str[t]);
if (t == CONST_IMM || t == PTR_TO_STACK)
- verbose("%d", env->cur_state.regs[i].imm);
+ verbose("%ld", env->cur_state.regs[i].imm);
else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
t == PTR_TO_MAP_VALUE_OR_NULL)
verbose("(ks=%d,vs=%d)",
@@ -477,7 +477,6 @@ static void init_reg_state(struct reg_state *regs)
for (i = 0; i < MAX_BPF_REG; i++) {
regs[i].type = NOT_INIT;
regs[i].imm = 0;
- regs[i].map_ptr = NULL;
}
/* frame pointer */
@@ -492,7 +491,6 @@ static void mark_reg_unknown_value(struct reg_state *regs,
u32 regno)
BUG_ON(regno >= MAX_BPF_REG);
regs[regno].type = UNKNOWN_VALUE;
regs[regno].imm = 0;
- regs[regno].map_ptr = NULL;
}
enum reg_arg_type {
--
2.8.0
