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Date: Tue, 11 Oct 2022 14:26:33 +0800 From: Xu Kuohai <xukuohai@...wei.com> To: Andrii Nakryiko <andrii.nakryiko@...il.com> CC: <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>, <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>, "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, Kumar Kartikeya Dwivedi <memxor@...il.com>, Alan Maguire <alan.maguire@...cle.com>, Delyan Kratunov <delyank@...com>, Lorenzo Bianconi <lorenzo@...nel.org> Subject: Re: [PATCH bpf v3 2/6] libbpf: Fix memory leak in parse_usdt_arg() On 10/11/2022 9:34 AM, Andrii Nakryiko wrote: > On Mon, Oct 10, 2022 at 7:08 AM Xu Kuohai <xukuohai@...wei.com> wrote: >> >> 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@...wei.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, ®_name, &off, &len) == 3) { >> + ret = sscanf(arg_str, " %d @ \[ %m[a-z0-9], %ld ] %n", &arg_sz, ®_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, ®_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, ®_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, ®_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, ®_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; >> + } >> } >> > > I think all this is more complicated than it has to be. How big can > register names be? Few characters? Let's get rid of %m[a-z0-9] and > instead use fixed-max-length strings, e.g., %5s. And read register > names into such local char buffers. It will simplify everything > tremendously. Let's use 16-byte buffers and use %15s to match it? > Would that be enough? > The valid register names accepted by calc_pt_regs_off() are x0~x31 and sp, so 16-byte buffer is enough. Since %15s matches all non-space characters, will use %15[a-z0-9] to match it. >> arg->arg_signed = arg_sz < 0; >> -- >> 2.30.2 >> > .
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