bpf: Clear percpu pointers in bpf_prog_clone_free()
Similar to bpf_prog_realloc(), bpf_prog_clone_create() also copies
the percpu pointers, but the clone still shares them with the original
prog, so we have to clear these two percpu pointers in
bpf_prog_clone_free(). Otherwise we would get a double free:
BUG: kernel NULL pointer dereference, address:
0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 13 PID: 8140 Comm: kworker/13:247 Kdump: loaded Tainted: G W OE
5.11.0-rc4.bm.1-amd64+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
test_bpf: #1 TXA
Workqueue: events bpf_prog_free_deferred
RIP: 0010:percpu_ref_get_many.constprop.97+0x42/0xf0
Code: [...]
RSP: 0018:
ffffa6bce1f9bda0 EFLAGS:
00010002
RAX:
0000000000000001 RBX:
0000000000000000 RCX:
00000000021dfc7b
RDX:
ffffffffae2eeb90 RSI:
867f92637e338da5 RDI:
0000000000000046
RBP:
ffffa6bce1f9bda8 R08:
0000000000000000 R09:
0000000000000001
R10:
0000000000000046 R11:
0000000000000000 R12:
0000000000000280
R13:
0000000000000000 R14:
0000000000000000 R15:
ffff9b5f3ffdedc0
FS:
0000000000000000(0000) GS:
ffff9b5f2fb40000(0000) knlGS:
0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
CR2:
0000000000000000 CR3:
000000027c36c002 CR4:
00000000003706e0
DR0:
0000000000000000 DR1:
0000000000000000 DR2:
0000000000000000
DR3:
0000000000000000 DR6:
00000000fffe0ff0 DR7:
0000000000000400
Call Trace:
refill_obj_stock+0x5e/0xd0
free_percpu+0xee/0x550
__bpf_prog_free+0x4d/0x60
process_one_work+0x26a/0x590
worker_thread+0x3c/0x390
? process_one_work+0x590/0x590
kthread+0x130/0x150
? kthread_park+0x80/0x80
ret_from_fork+0x1f/0x30
This bug is 100% reproducible with test_kmod.sh.
Fixes: 700d4796ef59 ("bpf: Optimize program stats")
Fixes: ca06f55b9002 ("bpf: Add per-program recursion prevention mechanism")
Reported-by: Jiang Wang <jiang.wang@bytedance.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210218001647.71631-1-xiyou.wangcong@gmail.com