1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
|
# First, write to an entry of /proc/sys. It should work fine.
r0 = openat$tcp_congestion(AUTO, &AUTO='/proc/sys/net/ipv4/tcp_congestion_control', AUTO, AUTO)
r1 = write$tcp_congestion(r0, &AUTO='reno\x00', AUTO)
# Now, load a BPF_PROG_TYPE_CGROUP_SYSCTL that simply returns 0, which will block all writes to /proc/sys
r2 = bpf$PROG_LOAD(AUTO, &AUTO={0x17, AUTO, &AUTO=@framed={{AUTO, AUTO, AUTO, AUTO, 0x0, AUTO, AUTO, AUTO, 0x0}, [], AUTO}, &AUTO='GPL\x00', 0x0, 0x0, 0x0, 0x0, 0x0, "00000000000000000000000000000000", 0x0, @cgroup_sysctl=0x12, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @void, @value=AUTO}, 0xa0)
r3 = openat(0xffffffffffffff9c, &AUTO='./cgroup\x00', 0x0, 0x0)
r4 = bpf$BPF_PROG_ATTACH(AUTO, &AUTO={@cgroup=r3, r2, 0x12, 0x0, 0x0, @void, @value=0x0, @void, @void, 0x0}, AUTO)
# It should fail now.
r5 = write$tcp_congestion(r0, &AUTO='reno\x00', AUTO) # EPERM
# Detach the BPF program.
r6 = bpf$BPF_PROG_DETACH(AUTO, &AUTO={@cgroup=r3, r2, 0x12, 0x0, 0x0, @void, @value=0x0, @void, @void, 0x0}, AUTO)
# It should work again.
r7 = write$tcp_congestion(r0, &AUTO='reno\x00', AUTO)
|
