Commit 6899b32b authored Apr 23, 2018 by Roman Gushchin Committed by Daniel Borkmann Apr 23, 2018

bpf: disable and restore preemption in __BPF_PROG_RUN_ARRAY



Running bpf programs requires disabled preemption,
however at least some* of the BPF_PROG_RUN_ARRAY users
do not follow this rule.

To fix this bug, and also to make it not happen in the future,
let's add explicit preemption disabling/re-enabling
to the __BPF_PROG_RUN_ARRAY code.

* for example:
 [   17.624472] RIP: 0010:__cgroup_bpf_run_filter_sk+0x1c4/0x1d0
 ...
 [   17.640890]  inet6_create+0x3eb/0x520
 [   17.641405]  __sock_create+0x242/0x340
 [   17.641939]  __sys_socket+0x57/0xe0
 [   17.642370]  ? trace_hardirqs_off_thunk+0x1a/0x1c
 [   17.642944]  SyS_socket+0xa/0x10
 [   17.643357]  do_syscall_64+0x79/0x220
 [   17.643879]  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 77621f02

include/linux/bpf.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -351,6 +351,7 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
		struct bpf_prog *_prog, __prog; \
		struct bpf_prog_array *_array; \
		u32 _ret = 1; \
		preempt_disable(); \
		rcu_read_lock(); \
		_array = rcu_dereference(array); \
		if (unlikely(check_non_null && !_array))\
		@@ -362,6 +363,7 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
		} \
		_out: \
		rcu_read_unlock(); \
		preempt_enable_no_resched(); \
		_ret; \
		})

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