Re: [PATCH v2] iptables: open eBPF programs in read only mode
From: Jakub Kicinski <kuba@kernel.org>
Date: 2020-03-26 18:30:51
Also in:
netfilter-devel
On Thu, 26 Mar 2020 07:28:03 -0700 Maciej Żenczykowski wrote:
quoted hunk ↗ jump to hunk
diff --git a/extensions/libxt_bpf.c b/extensions/libxt_bpf.c index 92958247..44cdd5cb 100644 --- a/extensions/libxt_bpf.c +++ b/extensions/libxt_bpf.c@@ -61,11 +61,22 @@ static const struct xt_option_entry bpf_opts_v1[] = { XTOPT_TABLEEND, }; -static int bpf_obj_get(const char *filepath) +static int bpf_obj_get_readonly(const char *filepath) { #if defined HAVE_LINUX_BPF_H && defined __NR_bpf && defined BPF_FS_MAGIC union bpf_attr attr; + // file_flags && BPF_F_RDONLY requires Linux 4.15+ uapi kernel headers +#ifdef BPF_F_RDONLY
FWIW the BPF subsystem is about to break uAPI backward-compat and
replace the defines with enums. See commit 1aae4bdd7879 ("bpf: Switch
BPF UAPI #define constants used from BPF program side to enums").
+ int fd; + memset(&attr, 0, sizeof(attr)); + attr.pathname = (__u64) filepath; + attr.file_flags = BPF_F_RDONLY; + fd = syscall(__NR_bpf, BPF_OBJ_GET, &attr, sizeof(attr)); + if (fd >= 0) return fd; + + // on any error fallback to default R/W access for pre-4.15-rc1 kernels +#endif