6.6-stable review patch. If anyone has any objections, please let me know.
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From: Andrii Nakryiko andrii@kernel.org
[ Upstream commit ab125ed3ec1c10ccc36bc98c7a4256ad114a3dae ]
When register is spilled onto a stack as a 1/2/4-byte register, we set slot_type[BPF_REG_SIZE - 1] (plus potentially few more below it, depending on actual spill size). So to check if some stack slot has spilled register we need to consult slot_type[7], not slot_type[0].
To avoid the need to remember and double-check this in the future, just use is_spilled_reg() helper.
Fixes: 27113c59b6d0 ("bpf: Check the other end of slot_type for STACK_SPILL") Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20231205184248.1502704-4-andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2deae0db03e8..24152ac6a393 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4330,7 +4330,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, * so it's aligned access and [off, off + size) are within stack limits */ if (!env->allow_ptr_leaks && - state->stack[spi].slot_type[0] == STACK_SPILL && + is_spilled_reg(&state->stack[spi]) && size != BPF_REG_SIZE) { verbose(env, "attempt to corrupt spilled pointer on stack\n"); return -EACCES;