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>

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 50da680..ad7a057 100644 (file)
--- 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,
 };

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 413ec56..6855878 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -62,17 +62,21 @@ EXPORT_SYMBOL_GPL(trace_call_bpf);
 static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 {
        void *dst = (void *) (long) r1;
-       int size = (int) r2;
+       int ret, size = (int) r2;
        void *unsafe_ptr = (void *) (long) r3;
 
-       return probe_kernel_read(dst, unsafe_ptr, size);
+       ret = probe_kernel_read(dst, unsafe_ptr, size);
+       if (unlikely(ret < 0))
+               memset(dst, 0, size);
+
+       return ret;
 }
 
 static const struct bpf_func_proto bpf_probe_read_proto = {
        .func           = bpf_probe_read,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
-       .arg1_type      = ARG_PTR_TO_STACK,
+       .arg1_type      = ARG_PTR_TO_RAW_STACK,
        .arg2_type      = ARG_CONST_STACK_SIZE,
        .arg3_type      = ARG_ANYTHING,
 };

diff --git a/net/core/filter.c b/net/core/filter.c
index e8486ba..5d2ac2b 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1409,16 +1409,19 @@ static u64 bpf_skb_load_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
        unsigned int len = (unsigned int) r4;
        void *ptr;
 
-       if (unlikely((u32) offset > 0xffff || len > MAX_BPF_STACK))
-               return -EFAULT;
+       if (unlikely((u32) offset > 0xffff))
+               goto err_clear;
 
        ptr = skb_header_pointer(skb, offset, len, to);
        if (unlikely(!ptr))
-               return -EFAULT;
+               goto err_clear;
        if (ptr != to)
                memcpy(to, ptr, len);
 
        return 0;
+err_clear:
+       memset(to, 0, len);
+       return -EFAULT;
 }
 
 static const struct bpf_func_proto bpf_skb_load_bytes_proto = {
@@ -1427,7 +1430,7 @@ static const struct bpf_func_proto bpf_skb_load_bytes_proto = {
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
-       .arg3_type      = ARG_PTR_TO_STACK,
+       .arg3_type      = ARG_PTR_TO_RAW_STACK,
        .arg4_type      = ARG_CONST_STACK_SIZE,
 };
 
@@ -1756,12 +1759,19 @@ static u64 bpf_skb_get_tunnel_key(u64 r1, u64 r2, u64 size, u64 flags, u64 r5)
        struct bpf_tunnel_key *to = (struct bpf_tunnel_key *) (long) r2;
        const struct ip_tunnel_info *info = skb_tunnel_info(skb);
        u8 compat[sizeof(struct bpf_tunnel_key)];
+       void *to_orig = to;
+       int err;
 
-       if (unlikely(!info || (flags & ~(BPF_F_TUNINFO_IPV6))))
-               return -EINVAL;
-       if (ip_tunnel_info_af(info) != bpf_tunnel_key_af(flags))
-               return -EPROTO;
+       if (unlikely(!info || (flags & ~(BPF_F_TUNINFO_IPV6)))) {
+               err = -EINVAL;
+               goto err_clear;
+       }
+       if (ip_tunnel_info_af(info) != bpf_tunnel_key_af(flags)) {
+               err = -EPROTO;
+               goto err_clear;
+       }
        if (unlikely(size != sizeof(struct bpf_tunnel_key))) {
+               err = -EINVAL;
                switch (size) {
                case offsetof(struct bpf_tunnel_key, tunnel_label):
                case offsetof(struct bpf_tunnel_key, tunnel_ext):
@@ -1771,12 +1781,12 @@ static u64 bpf_skb_get_tunnel_key(u64 r1, u64 r2, u64 size, u64 flags, u64 r5)
                         * a common path later on.
                         */
                        if (ip_tunnel_info_af(info) != AF_INET)
-                               return -EINVAL;
+                               goto err_clear;
 set_compat:
                        to = (struct bpf_tunnel_key *)compat;
                        break;
                default:
-                       return -EINVAL;
+                       goto err_clear;
                }
        }
 
@@ -1793,9 +1803,12 @@ set_compat:
        }
 
        if (unlikely(size != sizeof(struct bpf_tunnel_key)))
-               memcpy((void *)(long) r2, to, size);
+               memcpy(to_orig, to, size);
 
        return 0;
+err_clear:
+       memset(to_orig, 0, size);
+       return err;
 }
 
 static const struct bpf_func_proto bpf_skb_get_tunnel_key_proto = {
@@ -1803,7 +1816,7 @@ static const struct bpf_func_proto bpf_skb_get_tunnel_key_proto = {
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
-       .arg2_type      = ARG_PTR_TO_STACK,
+       .arg2_type      = ARG_PTR_TO_RAW_STACK,
        .arg3_type      = ARG_CONST_STACK_SIZE,
        .arg4_type      = ARG_ANYTHING,
 };
@@ -1813,16 +1826,26 @@ static u64 bpf_skb_get_tunnel_opt(u64 r1, u64 r2, u64 size, u64 r4, u64 r5)
        struct sk_buff *skb = (struct sk_buff *) (long) r1;
        u8 *to = (u8 *) (long) r2;
        const struct ip_tunnel_info *info = skb_tunnel_info(skb);
+       int err;
 
        if (unlikely(!info ||
-                    !(info->key.tun_flags & TUNNEL_OPTIONS_PRESENT)))
-               return -ENOENT;
-       if (unlikely(size < info->options_len))
-               return -ENOMEM;
+                    !(info->key.tun_flags & TUNNEL_OPTIONS_PRESENT))) {
+               err = -ENOENT;
+               goto err_clear;
+       }
+       if (unlikely(size < info->options_len)) {
+               err = -ENOMEM;
+               goto err_clear;
+       }
 
        ip_tunnel_info_opts_get(to, info);
+       if (size > info->options_len)
+               memset(to + info->options_len, 0, size - info->options_len);
 
        return info->options_len;
+err_clear:
+       memset(to, 0, size);
+       return err;
 }
 
 static const struct bpf_func_proto bpf_skb_get_tunnel_opt_proto = {
@@ -1830,7 +1853,7 @@ static const struct bpf_func_proto bpf_skb_get_tunnel_opt_proto = {
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
-       .arg2_type      = ARG_PTR_TO_STACK,
+       .arg2_type      = ARG_PTR_TO_RAW_STACK,
        .arg3_type      = ARG_CONST_STACK_SIZE,
 };