diff mbox series

[bpf-next,v3,1/2] bpf: Fix ref_obj_id for dynptr data slices in verifier

Message ID 20220809175208.2224443-1-joannelkoong@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series [bpf-next,v3,1/2] bpf: Fix ref_obj_id for dynptr data slices in verifier | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next
netdev/apply fail Patch does not apply to bpf-next
bpf/vmtest-bpf-next-PR fail merge-conflict

Commit Message

Joanne Koong Aug. 9, 2022, 5:52 p.m. UTC 
When a data slice is obtained from a dynptr (through the bpf_dynptr_data API),
the ref obj id of the dynptr must be found and then associated with the data
slice.

The ref obj id of the dynptr must be found *before* the caller saved regs are
reset. Without this fix, the ref obj id tracking is not correct for
dynptrs that are at an offset from the frame pointer.

Please also note that the data slice's ref obj id must be assigned after the
ret types are parsed, since RET_PTR_TO_ALLOC_MEM-type return regs get
zero-marked.

Fixes: 34d4ef5775f776ec4b0d53a02d588bf3195cada6 ("bpf: Add dynptr data slices");
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 kernel/bpf/verifier.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

Comments

Alexei Starovoitov Aug. 9, 2022, 6:36 p.m. UTC | #1 
On Tue, Aug 9, 2022 at 10:52 AM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> When a data slice is obtained from a dynptr (through the bpf_dynptr_data API),
> the ref obj id of the dynptr must be found and then associated with the data
> slice.
>
> The ref obj id of the dynptr must be found *before* the caller saved regs are
> reset. Without this fix, the ref obj id tracking is not correct for
> dynptrs that are at an offset from the frame pointer.
>
> Please also note that the data slice's ref obj id must be assigned after the
> ret types are parsed, since RET_PTR_TO_ALLOC_MEM-type return regs get
> zero-marked.
>
> Fixes: 34d4ef5775f776ec4b0d53a02d588bf3195cada6 ("bpf: Add dynptr data slices");
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>

merge conflict. pls respin.
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 843a966cd02b..671786a56bb6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7342,6 +7342,23 @@  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 			}
 		}
 		break;
+	case BPF_FUNC_dynptr_data:
+		for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
+			if (arg_type_is_dynptr(fn->arg_type[i])) {
+				if (meta.ref_obj_id) {
+					verbose(env, "verifier internal error: meta.ref_obj_id already set\n");
+					return -EFAULT;
+				}
+				/* Find the id of the dynptr we're tracking the reference of */
+				meta.ref_obj_id = stack_slot_get_id(env, &regs[BPF_REG_1 + i]);
+				break;
+			}
+		}
+		if (i == MAX_BPF_FUNC_REG_ARGS) {
+			verbose(env, "verifier internal error: no dynptr in bpf_dynptr_data()\n");
+			return -EFAULT;
+		}
+		break;
 	}
 
 	if (err)
@@ -7473,7 +7490,7 @@  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	if (type_may_be_null(regs[BPF_REG_0].type))
 		regs[BPF_REG_0].id = ++env->id_gen;
 
-	if (is_ptr_cast_function(func_id)) {
+	if (is_ptr_cast_function(func_id) || func_id == BPF_FUNC_dynptr_data) {
 		/* For release_reference() */
 		regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id;
 	} else if (is_acquire_function(func_id, meta.map_ptr)) {
@@ -7485,21 +7502,6 @@  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		regs[BPF_REG_0].id = id;
 		/* For release_reference() */
 		regs[BPF_REG_0].ref_obj_id = id;
-	} else if (func_id == BPF_FUNC_dynptr_data) {
-		int dynptr_id = 0, i;
-
-		/* Find the id of the dynptr we're acquiring a reference to */
-		for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
-			if (arg_type_is_dynptr(fn->arg_type[i])) {
-				if (dynptr_id) {
-					verbose(env, "verifier internal error: multiple dynptr args in func\n");
-					return -EFAULT;
-				}
-				dynptr_id = stack_slot_get_id(env, &regs[BPF_REG_1 + i]);
-			}
-		}
-		/* For release_reference() */
-		regs[BPF_REG_0].ref_obj_id = dynptr_id;
 	}
 
 	do_refine_retval_range(regs, fn->ret_type, func_id, &meta);