| Message ID | 1459996761-2926623-1-git-send-email-ast@fb.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On 04/07/2016 04:39 AM, Alexei Starovoitov wrote: > 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 <daniel@iogearbox.net> > Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net>
From: Alexei Starovoitov <ast@fb.com> Date: Wed, 6 Apr 2016 19:39:21 -0700 > 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 <daniel@iogearbox.net> > Signed-off-by: Alexei Starovoitov <ast@kernel.org> Applied, thanks Daniel.
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 {
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 <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> --- kernel/bpf/verifier.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)