diff mbox

[net-next,PATCHv2] bpf: Output error message to logbuf when loading failure

Message ID 1445843588-143137-1-git-send-email-wangnan0@huawei.com
State New
Headers show

Commit Message

Wang Nan Oct. 26, 2015, 7:13 a.m. UTC 
Many reasons can make bpf_prog_load() return EINVAL. This patch utilizes
logbuf to deliver the actual reason of the failure.

Without this patch, it is very easy for user to pass an object with
"version" section not match the kernel version code, and the problem
is hard to determine from return code (EINVAL).

Signed-off-by: Wang Nan <wangnan0@huawei.com>

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Wu Fengguang <fengguang.wu@intel.com>
---
 kernel/bpf/syscall.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 3 deletions(-)

-- 
1.8.3.4

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Comments

Wang Nan Oct. 27, 2015, 3:42 a.m. UTC | #1 
On 2015/10/27 11:26, Alexei Starovoitov wrote:
> On Mon, Oct 26, 2015 at 07:13:08AM +0000, Wang Nan wrote:

>> Many reasons can make bpf_prog_load() return EINVAL. This patch utilizes

>> logbuf to deliver the actual reason of the failure.

>>

>> Without this patch, it is very easy for user to pass an object with

>> "version" section not match the kernel version code, and the problem

>> is hard to determine from return code (EINVAL).

>>

>> Signed-off-by: Wang Nan <wangnan0@huawei.com>

>> Cc: Alexei Starovoitov <ast@kernel.org>

>> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>

>> Cc: David S. Miller <davem@davemloft.net>

>> Cc: Wu Fengguang <fengguang.wu@intel.com>

> NACK

> for both implementation and design.

OK. Let perf to report error message.

Thank you.

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diff mbox

Patch

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 687dd6c..719d0cb 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -17,6 +17,7 @@ 
 #include <linux/license.h>
 #include <linux/filter.h>
 #include <linux/version.h>
+#include <linux/bug.h>
 
 int sysctl_unprivileged_bpf_disabled __read_mostly;
 
@@ -574,6 +575,35 @@  struct bpf_prog *bpf_prog_get(u32 ufd)
 }
 EXPORT_SYMBOL_GPL(bpf_prog_get);
 
+static void
+bpf_prog_load_note(union bpf_attr *attr, const char *fmt, ...)
+{
+	u32 log_level, log_size;
+	char __user *log_ubuf = NULL;
+	/* 64 chars should be long enough for a one line note. */
+	char log_buf[64];
+	va_list args;
+
+	log_ubuf = (char __user *) (unsigned long) attr->log_buf;
+	log_level = attr->log_level;
+	log_size = sizeof(log_buf);
+	if (attr->log_size < log_size)
+		log_size = attr->log_size;
+
+	if (log_level == 0 || !log_size || !log_ubuf)
+		return;
+
+	va_start(args, fmt);
+	vscnprintf(log_buf, log_size, fmt, args);
+	va_end(args);
+	log_buf[sizeof(log_buf) - 1] = '\0';
+
+	/* Don't need care the copying result too much */
+	WARN(copy_to_user(log_ubuf, log_buf, log_size),
+	     KERN_WARNING "Failed to copy BPF error note '%s' to log buffer\n",
+	     log_buf);
+}
+
 /* last field in 'union bpf_attr' used by this command */
 #define	BPF_PROG_LOAD_LAST_FIELD kern_version
 
@@ -597,12 +627,19 @@  static int bpf_prog_load(union bpf_attr *attr)
 	/* eBPF programs must be GPL compatible to use GPL-ed functions */
 	is_gpl = license_is_gpl_compatible(license);
 
-	if (attr->insn_cnt >= BPF_MAXINSNS)
+	if (attr->insn_cnt >= BPF_MAXINSNS) {
+		bpf_prog_load_note(attr, "Too many instructions: %d > %d\n",
+				   attr->insn_cnt, BPF_MAXINSNS);
 		return -EINVAL;
+	}
 
 	if (type == BPF_PROG_TYPE_KPROBE &&
-	    attr->kern_version != LINUX_VERSION_CODE)
+	    attr->kern_version != LINUX_VERSION_CODE) {
+		bpf_prog_load_note(attr,
+				   "Kernel version mismatch: 0x%x != 0x%x\n",
+				   attr->kern_version, LINUX_VERSION_CODE);
 		return -EINVAL;
+	}
 
 	if (type != BPF_PROG_TYPE_SOCKET_FILTER && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -631,8 +668,10 @@  static int bpf_prog_load(union bpf_attr *attr)
 
 	/* find program type: socket_filter vs tracing_filter */
 	err = find_prog_type(type, prog);
-	if (err < 0)
+	if (err < 0) {
+		bpf_prog_load_note(attr, "Invalid program type: %d\n", type);
 		goto free_prog;
+	}
 
 	/* run eBPF verifier */
 	err = bpf_check(&prog, attr);