diff mbox series

[bpf-next,v2,08/15] bpf: Assign ID to scalars on spill

Message ID 20240108205209.838365-9-maxtram95@gmail.com (mailing list archive)
State Accepted
Commit 26b560765e674c51db2cea88dc1882fce081443c
Delegated to: BPF
Headers show
Series Improvements for tracking scalars in the BPF verifier | expand

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Commit Message

Maxim Mikityanskiy Jan. 8, 2024, 8:52 p.m. UTC 
From: Maxim Mikityanskiy <maxim@isovalent.com>

Currently, when a scalar bounded register is spilled to the stack, its
ID is preserved, but only if was already assigned, i.e. if this register
was MOVed before.

Assign an ID on spill if none is set, so that equal scalars could be
tracked if a register is spilled to the stack and filled into another
register.

One test is adjusted to reflect the change in register IDs.

Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/verifier.c                                     | 8 +++++++-
 .../selftests/bpf/progs/verifier_direct_packet_access.c   | 2 +-
 2 files changed, 8 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4cd82a7c1318..055fa8096a08 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4505,9 +4505,15 @@  static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 
 	mark_stack_slot_scratched(env, spi);
 	if (reg && !(off % BPF_REG_SIZE) && register_is_bounded(reg) && env->bpf_capable) {
+		bool reg_value_fits;
+
+		reg_value_fits = get_reg_width(reg) <= BITS_PER_BYTE * size;
+		/* Make sure that reg had an ID to build a relation on spill. */
+		if (reg_value_fits)
+			assign_scalar_id_before_mov(env, reg);
 		save_register_state(env, state, spi, reg, size);
 		/* Break the relation on a narrowing spill. */
-		if (get_reg_width(reg) > BITS_PER_BYTE * size)
+		if (!reg_value_fits)
 			state->stack[spi].spilled_ptr.id = 0;
 	} else if (!reg && !(off % BPF_REG_SIZE) && is_bpf_st_mem(insn) &&
 		   insn->imm != 0 && env->bpf_capable) {
diff --git a/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c b/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c
index be95570ab382..28b602ac9cbe 100644
--- a/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c
+++ b/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c
@@ -568,7 +568,7 @@  l0_%=:	r0 = 0;						\
 
 SEC("tc")
 __description("direct packet access: test23 (x += pkt_ptr, 4)")
-__failure __msg("invalid access to packet, off=0 size=8, R5(id=2,off=0,r=0)")
+__failure __msg("invalid access to packet, off=0 size=8, R5(id=3,off=0,r=0)")
 __flag(BPF_F_ANY_ALIGNMENT)
 __naked void test23_x_pkt_ptr_4(void)
 {