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Date: Mon, 10 Oct 2022 18:34:33 -0700 From: Andrii Nakryiko <andrii.nakryiko@...il.com> To: Xu Kuohai <xukuohai@...wei.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 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? > arg->arg_signed = arg_sz < 0; > -- > 2.30.2 >
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