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authorShmulik Ladkani <shmulik.ladkani@gmail.com>2017-10-09 15:27:15 +0300
committerPablo Neira Ayuso <pablo@netfilter.org>2017-10-09 15:18:04 +0200
commit98589a0998b8b13c4a8fa1ccb0e62751a019faa5 (patch)
treef9f02a6b9343f4024291966a5eee20090ae318c5 /include
parent49f817d793d1bcc11d721881aac037b996feef5c (diff)
download96b-common-98589a0998b8b13c4a8fa1ccb0e62751a019faa5.tar.gz
netfilter: xt_bpf: Fix XT_BPF_MODE_FD_PINNED mode of 'xt_bpf_info_v1'
Commit 2c16d6033264 ("netfilter: xt_bpf: support ebpf") introduced support for attaching an eBPF object by an fd, with the 'bpf_mt_check_v1' ABI expecting the '.fd' to be specified upon each IPT_SO_SET_REPLACE call. However this breaks subsequent iptables calls: # iptables -A INPUT -m bpf --object-pinned /sys/fs/bpf/xxx -j ACCEPT # iptables -A INPUT -s 5.6.7.8 -j ACCEPT iptables: Invalid argument. Run `dmesg' for more information. That's because iptables works by loading existing rules using IPT_SO_GET_ENTRIES to userspace, then issuing IPT_SO_SET_REPLACE with the replacement set. However, the loaded 'xt_bpf_info_v1' has an arbitrary '.fd' number (from the initial "iptables -m bpf" invocation) - so when 2nd invocation occurs, userspace passes a bogus fd number, which leads to 'bpf_mt_check_v1' to fail. One suggested solution [1] was to hack iptables userspace, to perform a "entries fixup" immediatley after IPT_SO_GET_ENTRIES, by opening a new, process-local fd per every 'xt_bpf_info_v1' entry seen. However, in [2] both Pablo Neira Ayuso and Willem de Bruijn suggested to depricate the xt_bpf_info_v1 ABI dealing with pinned ebpf objects. This fix changes the XT_BPF_MODE_FD_PINNED behavior to ignore the given '.fd' and instead perform an in-kernel lookup for the bpf object given the provided '.path'. It also defines an alias for the XT_BPF_MODE_FD_PINNED mode, named XT_BPF_MODE_PATH_PINNED, to better reflect the fact that the user is expected to provide the path of the pinned object. Existing XT_BPF_MODE_FD_ELF behavior (non-pinned fd mode) is preserved. References: [1] https://marc.info/?l=netfilter-devel&m=150564724607440&w=2 [2] https://marc.info/?l=netfilter-devel&m=150575727129880&w=2 Reported-by: Rafael Buchbinder <rafi@rbk.ms> Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com> Acked-by: Willem de Bruijn <willemb@google.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/bpf.h5
-rw-r--r--include/uapi/linux/netfilter/xt_bpf.h1
2 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8390859e79e7..f1af7d63d678 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -368,6 +368,11 @@ static inline void __bpf_prog_uncharge(struct user_struct *user, u32 pages)
{
}
+static inline int bpf_obj_get_user(const char __user *pathname)
+{
+ return -EOPNOTSUPP;
+}
+
static inline struct net_device *__dev_map_lookup_elem(struct bpf_map *map,
u32 key)
{
diff --git a/include/uapi/linux/netfilter/xt_bpf.h b/include/uapi/linux/netfilter/xt_bpf.h
index b97725af2ac0..da161b56c79e 100644
--- a/include/uapi/linux/netfilter/xt_bpf.h
+++ b/include/uapi/linux/netfilter/xt_bpf.h
@@ -23,6 +23,7 @@ enum xt_bpf_modes {
XT_BPF_MODE_FD_PINNED,
XT_BPF_MODE_FD_ELF,
};
+#define XT_BPF_MODE_PATH_PINNED XT_BPF_MODE_FD_PINNED
struct xt_bpf_info_v1 {
__u16 mode;