Yonghong Song e1a75e94a3 bpf: Fix a rcu warning for bpffs map pretty-print ... [ Upstream commit ce880cb825 ] Running selftest ./btf_btf -p the kernel had the following warning: [ 51.528185] WARNING: CPU: 3 PID: 1756 at kernel/bpf/hashtab.c:717 htab_map_get_next_key+0x2eb/0x300 [ 51.529217] Modules linked in: [ 51.529583] CPU: 3 PID: 1756 Comm: test_btf Not tainted 5.9.0-rc1+ #878 [ 51.530346] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.el7.centos 04/01/2014 [ 51.531410] RIP: 0010:htab_map_get_next_key+0x2eb/0x300 ... [ 51.542826] Call Trace: [ 51.543119] map_seq_next+0x53/0x80 [ 51.543528] seq_read+0x263/0x400 [ 51.543932] vfs_read+0xad/0x1c0 [ 51.544311] ksys_read+0x5f/0xe0 [ 51.544689] do_syscall_64+0x33/0x40 [ 51.545116] entry_SYSCALL_64_after_hwframe+0x44/0xa9 The related source code in kernel/bpf/hashtab.c: 709 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key) 710 { 711 struct bpf_htab *htab = container_of(map, struct bpf_htab, map); 712 struct hlist_nulls_head *head; 713 struct htab_elem *l, *next_l; 714 u32 hash, key_size; 715 int i = 0; 716 717 WARN_ON_ONCE(!rcu_read_lock_held()); In kernel/bpf/inode.c, bpffs map pretty print calls map->ops->map_get_next_key() without holding a rcu_read_lock(), hence causing the above warning. To fix the issue, just surrounding map->ops->map_get_next_key() with rcu read lock. Fixes: a26ca7c982 ("bpf: btf: Add pretty print support to the basic arraymap") Reported-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Cc: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20200916004401.146277-1-yhs@fb.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-10-01 13:14:52 +02:00
..
arraymap.c	bpf: decouple btf from seq bpf fs dump and enable more maps	2018-08-13 00:52:45 +02:00
bpf_lru_list.c
bpf_lru_list.h	bpf: Only set node->ref = 1 if it has not been set	2017-09-01 09:57:39 -07:00
btf.c	bpf: Explicitly memset some bpf info structures declared on the stack	2020-04-02 15:28:23 +02:00
cgroup.c	bpf: introduce update_effective_progs()	2018-08-07 14:29:55 +02:00
core.c	bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K	2019-07-10 09:53:47 +02:00
cpumap.c	cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled	2020-05-02 17:25:53 +02:00
devmap.c	bpf: devmap: fix wrong interface selection in notifier_call	2019-12-01 09:17:01 +01:00
disasm.c	bpf: Remove struct bpf_verifier_env argument from print_bpf_insn	2018-03-23 17:38:57 +01:00
disasm.h	bpf: Remove struct bpf_verifier_env argument from print_bpf_insn	2018-03-23 17:38:57 +01:00
hashtab.c	bpf: Remove recursion prevention from rcu free callback	2020-10-01 13:14:34 +02:00
helpers.c	bpf: introduce the bpf_get_local_storage() helper function	2018-08-03 00:47:32 +02:00
inode.c	bpf: Fix a rcu warning for bpffs map pretty-print	2020-10-01 13:14:52 +02:00
local_storage.c	bpf: allocate local storage buffers using GFP_ATOMIC	2018-12-17 09:24:33 +01:00
lpm_trie.c	bpf: lpm_trie: check left child of last leftmost node for NULL	2019-07-03 13:14:48 +02:00
Makefile	bpf: silence warning messages in core	2019-07-26 09:14:06 +02:00
map_in_map.c	bpf: fix inner map masking to prevent oob under speculation	2019-01-31 08:14:41 +01:00
map_in_map.h
offload.c	bpf, offload: Replace bitwise AND by logical AND in bpf_prog_offload_info_fill	2020-02-28 16:38:59 +01:00
percpu_freelist.c	bpf: fix lockdep false positive in percpu_freelist	2019-03-13 14:02:36 -07:00
percpu_freelist.h	bpf: fix lockdep false positive in percpu_freelist	2019-03-13 14:02:36 -07:00
reuseport_array.c	bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY	2018-08-11 01:58:46 +02:00
sockmap.c	bpf: sockmap, fix transition through disconnect without close	2018-09-22 02:46:41 +02:00
stackmap.c	bpf/stackmap: Fix deadlock with rq_lock in bpf_get_stack()	2019-12-31 16:35:20 +01:00
syscall.c	bpf: Check correct cred for CAP_SYSLOG in bpf_dump_raw_ok()	2020-07-16 08:17:27 +02:00
tnum.c	bpf: Fix incorrect verifier simulation of ARSH under ALU32	2020-01-23 08:21:32 +01:00
verifier.c	bpf: fix buggy r0 retval refinement for tracing helpers	2020-04-23 10:30:24 +02:00
xskmap.c	xsk: do not call synchronize_net() under RCU read lock	2018-10-11 10:19:01 +02:00