[PATCH bpf v3 2/6] libbpf: Fix memory leak in parse_usdt_arg()

From: Xu Kuohai <xukuohai@huawei.com>
To: <bpf@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-kselftest@vger.kernel.org>, <netdev@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>, Mykola Lysenko <mykolal@fb.com>,
	Shuah Khan <shuah@kernel.org>,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Kumar Kartikeya Dwivedi <memxor@gmail.com>,
	Alan Maguire <alan.maguire@oracle.com>,
	Delyan Kratunov <delyank@fb.com>,
	Lorenzo Bianconi <lorenzo@kernel.org>
Subject: [PATCH bpf v3 2/6] libbpf: Fix memory leak in parse_usdt_arg()
Date: Mon, 10 Oct 2022 10:25:49 -0400	[thread overview]
Message-ID: <20221010142553.776550-3-xukuohai@huawei.com> (raw)
In-Reply-To: <20221010142553.776550-1-xukuohai@huawei.com>

In the arm64 version of parse_usdt_arg(), when sscanf returns 2, reg_name
is allocated but not freed. Fix it.

Fixes: 0f8619929c57 ("libbpf: Usdt aarch64 arg parsing support")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
---
 tools/lib/bpf/usdt.c | 59 +++++++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 26 deletions(-)

diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index e83b497c2245..f3b5be7415b5 100644
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -1351,8 +1351,10 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec
 	char *reg_name = NULL;
 	int arg_sz, len, reg_off;
 	long off;
+	int ret;
 
-	if (sscanf(arg_str, " %d @ \[ %m[a-z0-9], %ld ] %n", &arg_sz, &reg_name, &off, &len) == 3) {
+	ret = sscanf(arg_str, " %d @ \[ %m[a-z0-9], %ld ] %n", &arg_sz, &reg_name, &off, &len);
+	if (ret == 3) {
 		/* Memory dereference case, e.g., -4@[sp, 96] */
 		arg->arg_type = USDT_ARG_REG_DEREF;
 		arg->val_off = off;
@@ -1361,32 +1363,37 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec
 		if (reg_off < 0)
 			return reg_off;
 		arg->reg_off = reg_off;
-	} else if (sscanf(arg_str, " %d @ \[ %m[a-z0-9] ] %n", &arg_sz, &reg_name, &len) == 2) {
-		/* Memory dereference case, e.g., -4@[sp] */
-		arg->arg_type = USDT_ARG_REG_DEREF;
-		arg->val_off = 0;
-		reg_off = calc_pt_regs_off(reg_name);
-		free(reg_name);
-		if (reg_off < 0)
-			return reg_off;
-		arg->reg_off = reg_off;
-	} else if (sscanf(arg_str, " %d @ %ld %n", &arg_sz, &off, &len) == 2) {
-		/* Constant value case, e.g., 4@5 */
-		arg->arg_type = USDT_ARG_CONST;
-		arg->val_off = off;
-		arg->reg_off = 0;
-	} else if (sscanf(arg_str, " %d @ %m[a-z0-9] %n", &arg_sz, &reg_name, &len) == 2) {
-		/* Register read case, e.g., -8@x4 */
-		arg->arg_type = USDT_ARG_REG;
-		arg->val_off = 0;
-		reg_off = calc_pt_regs_off(reg_name);
-		free(reg_name);
-		if (reg_off < 0)
-			return reg_off;
-		arg->reg_off = reg_off;
 	} else {
-		pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
-		return -EINVAL;
+		if (ret == 2)
+			free(reg_name);
+
+		if (sscanf(arg_str, " %d @ \[ %m[a-z0-9] ] %n", &arg_sz, &reg_name, &len) == 2) {
+			/* Memory dereference case, e.g., -4@[sp] */
+			arg->arg_type = USDT_ARG_REG_DEREF;
+			arg->val_off = 0;
+			reg_off = calc_pt_regs_off(reg_name);
+			free(reg_name);
+			if (reg_off < 0)
+				return reg_off;
+			arg->reg_off = reg_off;
+		} else if (sscanf(arg_str, " %d @ %ld %n", &arg_sz, &off, &len) == 2) {
+			/* Constant value case, e.g., 4@5 */
+			arg->arg_type = USDT_ARG_CONST;
+			arg->val_off = off;
+			arg->reg_off = 0;
+		} else if (sscanf(arg_str, " %d @ %m[a-z0-9] %n", &arg_sz, &reg_name, &len) == 2) {
+			/* Register read case, e.g., -8@x4 */
+			arg->arg_type = USDT_ARG_REG;
+			arg->val_off = 0;
+			reg_off = calc_pt_regs_off(reg_name);
+			free(reg_name);
+			if (reg_off < 0)
+				return reg_off;
+			arg->reg_off = reg_off;
+		} else {
+			pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
+			return -EINVAL;
+		}
 	}
 
 	arg->arg_signed = arg_sz < 0;
-- 
2.30.2

