From 1955351da41caa1dbf4139191358fed84909d64b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Sat, 24 Sep 2016 20:01:50 +0200 Subject: bpf: Set register type according to is_valid_access() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This prevent future potential pointer leaks when an unprivileged eBPF program will read a pointer value from its context. Even if is_valid_access() returns a pointer type, the eBPF verifier replace it with UNKNOWN_VALUE. The register value that contains a kernel address is then allowed to leak. Moreover, this fix allows unprivileged eBPF programs to use functions with (legitimate) pointer arguments. Not an issue currently since reg_type is only set for PTR_TO_PACKET or PTR_TO_PACKET_END in XDP and TC programs that can only be loaded as privileged. For now, the only unprivileged eBPF program allowed is for socket filtering and all the types from its context are UNKNOWN_VALUE. However, this fix is important for future unprivileged eBPF programs which could use pointers in their context. Signed-off-by: Mickaël Salaün Cc: Alexei Starovoitov Cc: Daniel Borkmann Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/verifier.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8c3f794c7028..7ada3152a556 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -749,9 +749,8 @@ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, err = check_ctx_access(env, off, size, t, ®_type); if (!err && t == BPF_READ && value_regno >= 0) { mark_reg_unknown_value(state->regs, value_regno); - if (env->allow_ptr_leaks) - /* note that reg.[id|off|range] == 0 */ - state->regs[value_regno].type = reg_type; + /* note that reg.[id|off|range] == 0 */ + state->regs[value_regno].type = reg_type; } } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { -- cgit v1.2.3