Messages in this thread | | | Subject | Re: [PATCH -next] libbpf: Add additional null-pointer checking in make_parent_dir | From | cuigaosheng <> | Date | Fri, 22 Apr 2022 10:55:00 +0800 |
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This email adjusts the code format.
I don't understand why we don't check path for NULL, bpf_link__pin is an external interface, It will be called by external functions and provide input parameters, for example in samples/bpf/hbm.c:
> 201 link = bpf_program__attach_cgroup(bpf_prog, cg1); > 202 if (libbpf_get_error(link)) { > 203 fprintf(stderr, "ERROR: bpf_program__attach_cgroup > failed\n"); > 204 goto err; > 205 } > 206 > 207 sprintf(cg_pin_path, "/sys/fs/bpf/hbm%d", cg_id); > 208 rc = bpf_link__pin(link, cg_pin_path); > 209 if (rc < 0) { > 210 printf("ERROR: bpf_link__pin failed: %d\n", rc); > 211 goto err; > 212 }
if cg_pin_path is NULL, strdup(NULL) will trigger a segmentation fault in make_parent_dir, I think we should avoid this and add null-pointer checking for path, just like check_path: > 7673 static int check_path(const char *path) > 7674 { > 7675 char *cp, errmsg[STRERR_BUFSIZE]; > 7676 struct statfs st_fs; > 7677 char *dname, *dir; > 7678 int err = 0; > 7679 > 7680 if (path == NULL) > 7681 return -EINVAL; > 7682 > 7683 dname = strdup(path); > 7684 if (dname == NULL) > 7685 return -ENOMEM; > 7686 > 7687 dir = dirname(dname); > 7688 if (statfs(dir, &st_fs)) { > 7689 cp = libbpf_strerror_r(errno, errmsg, > sizeof(errmsg)); > 7690 pr_warn("failed to statfs %s: %s\n", dir, cp); > 7691 err = -errno; > 7692 } > 7693 free(dname); > 7694 > 7695 if (!err && st_fs.f_type != BPF_FS_MAGIC) { > 7696 pr_warn("specified path %s is not on BPF FS\n", > path); > 7697 err = -EINVAL; > 7698 } > 7699 > 7700 return err; > 7701 }
Thanks.
在 2022/4/22 0:55, Andrii Nakryiko 写道: > On Thu, Apr 21, 2022 at 6:01 AM Gaosheng Cui <cuigaosheng1@huawei.com> wrote: >> The make_parent_dir is called without null-pointer checking for path, >> such as bpf_link__pin. To ensure there is no null-pointer dereference >> in make_parent_dir, so make_parent_dir requires additional null-pointer >> checking for path. >> >> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com> >> --- >> tools/lib/bpf/libbpf.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c >> index b53e51884f9e..5786e6184bf5 100644 >> --- a/tools/lib/bpf/libbpf.c >> +++ b/tools/lib/bpf/libbpf.c >> @@ -7634,6 +7634,9 @@ static int make_parent_dir(const char *path) >> char *dname, *dir; >> int err = 0; >> >> + if (path == NULL) >> + return -EINVAL; >> + > API contract is that path shouldn't be NULL. Just like we don't check > link, obj, prog for NULL in every single API, I don't think we need to > do it here, unless I'm missing something? > >> dname = strdup(path); >> if (dname == NULL) >> return -ENOMEM; >> -- >> 2.25.1 >> > .
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