Yonghong Song ce880cb825 bpf: Fix a rcu warning for bpffs map pretty-print ...

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: a26ca7c982cb ("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

2020-09-15 18:17:39 -07:00

..

arraymap.c

bpf: Implement bpf iterator for array maps

2020-07-25 20:16:33 -07:00

bpf_iter.c

bpf: Fix a rcu_sched stall issue with bpf task/task_file iterator

2020-08-18 17:36:23 -07:00

bpf_lru_list.c

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206

2019-05-30 11:29:53 -07:00

bpf_lru_list.h

bpf: Fix a typo "inacitve" -> "inactive"

2020-04-06 21:54:10 +02:00

bpf_lsm.c

bpf: Use tracing helpers for lsm programs

2020-06-01 15:08:04 -07:00

bpf_struct_ops_types.h

bpf: tcp: Support tcp_congestion_ops in bpf

2020-01-09 08:46:18 -08:00

bpf_struct_ops.c

bpf: Set map_btf_{name, id} for all map types

2020-06-22 22:22:58 +02:00

btf.c

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2020-08-03 18:27:40 -07:00

cgroup.c

bpf: Add support for forced LINK_DETACH command

2020-08-01 20:38:28 -07:00

core.c

bpf: Delete repeated words in comments

2020-08-07 18:57:24 +02:00

cpumap.c

bpf: cpumap: Fix possible rcpu kthread hung

2020-07-21 09:15:28 -07:00

devmap.c

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2020-07-04 17:48:34 -07:00

disasm.c

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 295

2019-06-05 17:36:38 +02:00

disasm.h

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 295

2019-06-05 17:36:38 +02:00

dispatcher.c

bpf: Remove bpf_image tree

2020-03-13 12:49:52 -07:00

hashtab.c

bpf: Do not use bucket_lock for hashmap iterator

2020-09-03 17:36:41 -07:00

helpers.c

bpf: Implement BPF ring buffer and verifier support for it

2020-06-01 14:38:22 -07:00

inode.c

bpf: Fix a rcu warning for bpffs map pretty-print

2020-09-15 18:17:39 -07:00

local_storage.c

bpf/local_storage: Fix build without CONFIG_CGROUP

2020-07-25 20:16:36 -07:00

lpm_trie.c

bpf: Remove redundant synchronize_rcu.

2020-07-01 08:07:13 -07:00

Makefile

bpf: Add bpf_prog iterator

2020-07-25 20:16:32 -07:00

map_in_map.c

bpf: Implement CAP_BPF

2020-05-15 17:29:41 +02:00

map_in_map.h

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206

2019-05-30 11:29:53 -07:00

map_iter.c

bpf: Change uapi for bpf iterator map elements

2020-08-06 16:39:14 -07:00

net_namespace.c

bpf: Add support for forced LINK_DETACH command

2020-08-01 20:38:28 -07:00

offload.c

bpf, offload: Replace bitwise AND by logical AND in bpf_prog_offload_info_fill

2020-02-17 16:53:49 +01:00

percpu_freelist.c

bpf: Dont iterate over possible CPUs with interrupts disabled

2020-02-24 16:18:20 -08:00

percpu_freelist.h

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206

2019-05-30 11:29:53 -07:00

prog_iter.c

bpf: Refactor bpf_iter_reg to have separate seq_info member

2020-07-25 20:16:32 -07:00

queue_stack_maps.c

bpf: Remove redundant synchronize_rcu.

2020-07-01 08:07:13 -07:00

reuseport_array.c

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2020-07-11 00:46:00 -07:00

ringbuf.c

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2020-07-11 00:46:00 -07:00

stackmap.c

bpf: Iterate through all PT_NOTE sections when looking for build id

2020-08-12 18:14:49 -07:00

syscall.c

bpf: Fix a buffer out-of-bound access when filling raw_tp link_info

2020-08-24 21:03:07 -07:00

sysfs_btf.c

bpf: Support llvm-objcopy for vmlinux BTF

2020-03-19 12:32:38 +01:00

task_iter.c

bpf: Avoid visit same object multiple times

2020-08-18 17:36:23 -07:00

tnum.c

bpf: Verifier, do explicit ALU32 bounds tracking

2020-03-30 14:59:53 -07:00

trampoline.c

bpf: lsm: Implement attach, detach and execution

2020-03-30 01:34:00 +02:00

verifier.c

bpf: Delete repeated words in comments

2020-08-07 18:57:24 +02:00