[PATCH 5.15 269/279] bpf: Forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing progs

Greg Kroah-Hartman
2021-11-24T14:09:24Z

From: Dmitrii Banshchikov <me@ubique.spb.ru>

commit 5e0bc3082e2e403ac0753e099c2b01446bb35578 upstream.

Use of bpf_ktime_get_coarse_ns() and bpf_timer_* helpers in tracing
progs may result in locking issues.

bpf_ktime_get_coarse_ns() uses ktime_get_coarse_ns() time accessor that
isn't safe for any context:
======================================================
WARNING: possible circular locking dependency detected
5.15.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/14877 is trying to acquire lock:
ffffffff8cb30008 (tk_core.seq.seqcount){----}-{0:0}, at: ktime_get_coarse_ts64+0x25/0x110 kernel/time/timekeeping.c:2255

but task is already holding lock:
ffffffff90dbf200 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_deactivate+0x61/0x400 lib/debugobjects.c:735

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&obj_hash[i].lock){-.-.}-{2:2}:
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
__debug_object_init+0xd9/0x1860 lib/debugobjects.c:569
debug_hrtimer_init kernel/time/hrtimer.c:414 [inline]
debug_init kernel/time/hrtimer.c:468 [inline]
hrtimer_init+0x20/0x40 kernel/time/hrtimer.c:1592
ntp_init_cmos_sync kernel/time/ntp.c:676 [inline]
ntp_init+0xa1/0xad kernel/time/ntp.c:1095
timekeeping_init+0x512/0x6bf kernel/time/timekeeping.c:1639
start_kernel+0x267/0x56e init/main.c:1030
secondary_startup_64_no_verify+0xb1/0xbb

-> #0 (tk_core.seq.seqcount){----}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3051 [inline]
check_prevs_add kernel/locking/lockdep.c:3174 [inline]
validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3789
__lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5015
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
seqcount_lockdep_reader_access+0xfe/0x230 include/linux/seqlock.h:103
ktime_get_coarse_ts64+0x25/0x110 kernel/time/timekeeping.c:2255
ktime_get_coarse include/linux/timekeeping.h:120 [inline]
ktime_get_coarse_ns include/linux/timekeeping.h:126 [inline]
____bpf_ktime_get_coarse_ns kernel/bpf/helpers.c:173 [inline]
bpf_ktime_get_coarse_ns+0x7e/0x130 kernel/bpf/helpers.c:171
bpf_prog_a99735ebafdda2f1+0x10/0xb50
bpf_dispatcher_nop_func include/linux/bpf.h:721 [inline]
__bpf_prog_run include/linux/filter.h:626 [inline]
bpf_prog_run include/linux/filter.h:633 [inline]
BPF_PROG_RUN_ARRAY include/linux/bpf.h:1294 [inline]
trace_call_bpf+0x2cf/0x5d0 kernel/trace/bpf_trace.c:127
perf_trace_run_bpf_submit+0x7b/0x1d0 kernel/events/core.c:9708
perf_trace_lock+0x37c/0x440 include/trace/events/lock.h:39
trace_lock_release+0x128/0x150 include/trace/events/lock.h:58
lock_release+0x82/0x810 kernel/locking/lockdep.c:5636
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
_raw_spin_unlock_irqrestore+0x75/0x130 kernel/locking/spinlock.c:194
debug_hrtimer_deactivate kernel/time/hrtimer.c:425 [inline]
debug_deactivate kernel/time/hrtimer.c:481 [inline]
__run_hrtimer kernel/time/hrtimer.c:1653 [inline]
__hrtimer_run_queues+0x2f9/0xa60 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x3b3/0x1040 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline]
__sysvec_apic_timer_interrupt+0xf9/0x270 arch/x86/kernel/apic/apic.c:1103
sysvec_apic_timer_interrupt+0x8c/0xb0 arch/x86/kernel/apic/apic.c:1097
asm_sysvec_apic_timer_interrupt+0x12/0x20
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock_irqrestore+0xd4/0x130 kernel/locking/spinlock.c:194
try_to_wake_up+0x702/0xd20 kernel/sched/core.c:4118
wake_up_process kernel/sched/core.c:4200 [inline]
wake_up_q+0x9a/0xf0 kernel/sched/core.c:953
futex_wake+0x50f/0x5b0 kernel/futex/waitwake.c:184
do_futex+0x367/0x560 kernel/futex/syscalls.c:127
__do_sys_futex kernel/futex/syscalls.c:199 [inline]
__se_sys_futex+0x401/0x4b0 kernel/futex/syscalls.c:180
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

There is a possible deadlock with bpf_timer_* set of helpers:
hrtimer_start()
lock_base();
trace_hrtimer...()
perf_event()
bpf_run()
bpf_timer_start()
hrtimer_start()
lock_base() <- DEADLOCK

Forbid use of bpf_ktime_get_coarse_ns() and bpf_timer_* helpers in
BPF_PROG_TYPE_KPROBE, BPF_PROG_TYPE_TRACEPOINT, BPF_PROG_TYPE_PERF_EVENT
and BPF_PROG_TYPE_RAW_TRACEPOINT prog types.

Fixes: d05512618056 ("bpf: Add bpf_ktime_get_coarse_ns helper")
Fixes: b00628b1c7d5 ("bpf: Introduce bpf timers.")
Reported-by: syzbot+43fd005b5a1b4d10781e@syzkaller.appspotmail.com
Signed-off-by: Dmitrii Banshchikov <me@ubique.spb.ru>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211113142227.566439-2-me@ubique.spb.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/cgroup.c | 2 ++
kernel/bpf/helpers.c | 2 --
kernel/bpf/verifier.c | 7 +++++++
kernel/trace/bpf_trace.c | 2 --
net/core/filter.c | 6 ++++++
net/ipv4/bpf_tcp_ca.c | 2 ++
6 files changed, 17 insertions(+), 4 deletions(-)

--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1773,6 +1773,8 @@ sysctl_func_proto(enum bpf_func_id func_
return &bpf_sysctl_get_new_value_proto;
case BPF_FUNC_sysctl_set_new_value:
return &bpf_sysctl_set_new_value_proto;
+ case BPF_FUNC_ktime_get_coarse_ns:
+ return &bpf_ktime_get_coarse_ns_proto;
default:
return cgroup_base_func_proto(func_id, prog);
}
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1367,8 +1367,6 @@ bpf_base_func_proto(enum bpf_func_id fun
return &bpf_ktime_get_ns_proto;
case BPF_FUNC_ktime_get_boot_ns:
return &bpf_ktime_get_boot_ns_proto;
- case BPF_FUNC_ktime_get_coarse_ns:
- return &bpf_ktime_get_coarse_ns_proto;
case BPF_FUNC_ringbuf_output:
return &bpf_ringbuf_output_proto;
case BPF_FUNC_ringbuf_reserve:
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11451,6 +11451,13 @@ static int check_map_prog_compatibility(
}
}

+ if (map_value_has_timer(map)) {
+ if (is_tracing_prog_type(prog_type)) {
+ verbose(env, "tracing progs cannot use bpf_timer yet\n");
+ return -EINVAL;
+ }
+ }
+
if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) &&
!bpf_offload_prog_map_match(prog, map)) {
verbose(env, "offload device mismatch between prog and map\n");
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1037,8 +1037,6 @@ bpf_tracing_func_proto(enum bpf_func_id
return &bpf_ktime_get_ns_proto;
case BPF_FUNC_ktime_get_boot_ns:
return &bpf_ktime_get_boot_ns_proto;
- case BPF_FUNC_ktime_get_coarse_ns:
- return &bpf_ktime_get_coarse_ns_proto;
case BPF_FUNC_tail_call:
return &bpf_tail_call_proto;
case BPF_FUNC_get_current_pid_tgid:
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7162,6 +7162,8 @@ sock_filter_func_proto(enum bpf_func_id
#endif
case BPF_FUNC_sk_storage_get:
return &bpf_sk_storage_get_cg_sock_proto;
+ case BPF_FUNC_ktime_get_coarse_ns:
+ return &bpf_ktime_get_coarse_ns_proto;
default:
return bpf_base_func_proto(func_id);
}
@@ -10306,6 +10308,8 @@ sk_reuseport_func_proto(enum bpf_func_id
return &sk_reuseport_load_bytes_relative_proto;
case BPF_FUNC_get_socket_cookie:
return &bpf_get_socket_ptr_cookie_proto;
+ case BPF_FUNC_ktime_get_coarse_ns:
+ return &bpf_ktime_get_coarse_ns_proto;
default:
return bpf_base_func_proto(func_id);
}
@@ -10787,6 +10791,8 @@ bpf_sk_base_func_proto(enum bpf_func_id
case BPF_FUNC_skc_to_udp6_sock:
func = &bpf_skc_to_udp6_sock_proto;
break;
+ case BPF_FUNC_ktime_get_coarse_ns:
+ return &bpf_ktime_get_coarse_ns_proto;
default:
return bpf_base_func_proto(func_id);
}
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -212,6 +212,8 @@ bpf_tcp_ca_get_func_proto(enum bpf_func_
offsetof(struct tcp_congestion_ops, release))
return &bpf_sk_getsockopt_proto;
return NULL;
+ case BPF_FUNC_ktime_get_coarse_ns:
+ return &bpf_ktime_get_coarse_ns_proto;
default:
return bpf_base_func_proto(func_id);
}