2022-10-09 13:03:34

by Xu Kuohai

Subject: [PATCH bpf-next 2/5] libbpf: Fix memory leak in parse_usdt_arg()

From: Xu Kuohai <[email protected]>

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

Signed-off-by: Xu Kuohai <[email protected]>
---
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;
--
2.25.1