bpf: convert relevant helper args to ARG_PTR_TO_RAW_STACK

This patch converts all helpers that can use ARG_PTR_TO_RAW_STACK as argument
type. For tc programs this is bpf_skb_load_bytes(), bpf_skb_get_tunnel_key(),
bpf_skb_get_tunnel_opt(). For tracing, this optimizes bpf_get_current_comm()
and bpf_probe_read(). The check in bpf_skb_load_bytes() for MAX_BPF_STACK can
also be removed since the verifier already makes sure we stay within bounds
on stack buffers.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 4 deletions

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 50da680c479f..ad7a0573f71b 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -163,17 +163,26 @@ static u64 bpf_get_current_comm(u64 r1, u64 size, u64 r3, u64 r4, u64 r5)
         struct task_struct *task = current;
         char *buf = (char *) (long) r1;
 
-        if (!task)
-                return -EINVAL;
+        if (unlikely(!task))
+                goto err_clear;
 
-        strlcpy(buf, task->comm, min_t(size_t, size, sizeof(task->comm)));
+        strncpy(buf, task->comm, size);
+
+        /* Verifier guarantees that size > 0. For task->comm exceeding
+         * size, guarantee that buf is %NUL-terminated. Unconditionally
+         * done here to save the size test.
+         */
+        buf[size - 1] = 0;
         return 0;
+err_clear:
+        memset(buf, 0, size);
+        return -EINVAL;
 }
 
 const struct bpf_func_proto bpf_get_current_comm_proto = {
         .func           = bpf_get_current_comm,
         .gpl_only       = false,
         .ret_type       = RET_INTEGER,
-        .arg1_type      = ARG_PTR_TO_STACK,
+        .arg1_type      = ARG_PTR_TO_RAW_STACK,
         .arg2_type      = ARG_CONST_STACK_SIZE,
 };