Yonghong Song b9aff38de2 bpf: Fix a potential deadlock with bpf_map_do_batch ... Commit 057996380a ("bpf: Add batch ops to all htab bpf map") added lookup_and_delete batch operation for hash table. The current implementation has bpf_lru_push_free() inside the bucket lock, which may cause a deadlock. syzbot reports: -> #2 (&htab->buckets[i].lock#2){....}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:159 htab_lru_map_delete_node+0xce/0x2f0 kernel/bpf/hashtab.c:593 __bpf_lru_list_shrink_inactive kernel/bpf/bpf_lru_list.c:220 [inline] __bpf_lru_list_shrink+0xf9/0x470 kernel/bpf/bpf_lru_list.c:266 bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:340 [inline] bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline] bpf_lru_pop_free+0x87c/0x1670 kernel/bpf/bpf_lru_list.c:499 prealloc_lru_pop+0x2c/0xa0 kernel/bpf/hashtab.c:132 __htab_lru_percpu_map_update_elem+0x67e/0xa90 kernel/bpf/hashtab.c:1069 bpf_percpu_hash_update+0x16e/0x210 kernel/bpf/hashtab.c:1585 bpf_map_update_value.isra.0+0x2d7/0x8e0 kernel/bpf/syscall.c:181 generic_map_update_batch+0x41f/0x610 kernel/bpf/syscall.c:1319 bpf_map_do_batch+0x3f5/0x510 kernel/bpf/syscall.c:3348 __do_sys_bpf+0x9b7/0x41e0 kernel/bpf/syscall.c:3460 __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:3355 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&loc_l->lock){....}: check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain kernel/locking/lockdep.c:2970 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3954 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4484 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:159 bpf_common_lru_push_free kernel/bpf/bpf_lru_list.c:516 [inline] bpf_lru_push_free+0x250/0x5b0 kernel/bpf/bpf_lru_list.c:555 __htab_map_lookup_and_delete_batch+0x8d4/0x1540 kernel/bpf/hashtab.c:1374 htab_lru_map_lookup_and_delete_batch+0x34/0x40 kernel/bpf/hashtab.c:1491 bpf_map_do_batch+0x3f5/0x510 kernel/bpf/syscall.c:3348 __do_sys_bpf+0x1f7d/0x41e0 kernel/bpf/syscall.c:3456 __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:3355 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe Possible unsafe locking scenario: CPU0 CPU2 ---- ---- lock(&htab->buckets[i].lock#2); lock(&l->lock); lock(&htab->buckets[i].lock#2); lock(&loc_l->lock); *** DEADLOCK *** To fix the issue, for htab_lru_map_lookup_and_delete_batch() in CPU0, let us do bpf_lru_push_free() out of the htab bucket lock. This can avoid the above deadlock scenario. Fixes: 057996380a ("bpf: Add batch ops to all htab bpf map") Reported-by: syzbot+a38ff3d9356388f2fb83@syzkaller.appspotmail.com Reported-by: syzbot+122b5421d14e68f29cd1@syzkaller.appspotmail.com Suggested-by: Hillf Danton <hdanton@sina.com> Suggested-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com> Acked-by: Brian Vazquez <brianvv@google.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20200219234757.3544014-1-yhs@fb.com		2020-02-19 16:01:25 -08:00
..
arraymap.c	bpf: Add lookup and update batch ops to arraymap	2020-01-15 14:00:35 -08:00
bpf_lru_list.c
bpf_lru_list.h
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: Reuse log from btf_prase_vmlinux() in btf_struct_ops_init()	2020-01-29 16:40:54 +01:00
btf.c	bpf: Make btf_check_func_type_match() static	2020-02-11 00:22:47 +01:00
cgroup.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net	2020-01-09 12:13:43 -08:00
core.c	bpf: Add BPF_FUNC_jiffies64	2020-01-22 16:30:10 -08:00
cpumap.c	xdp: Make cpumap flush_list common for all map instances	2019-12-19 21:09:43 -08:00
devmap.c	bpf, xdp: Remove no longer required rcu_read_{un}lock()	2020-01-27 11:16:25 +01:00
disasm.c
disasm.h
dispatcher.c	bpf: Allow to resolve bpf trampoline and dispatcher in unwind	2020-01-25 07:12:40 -08:00
hashtab.c	bpf: Fix a potential deadlock with bpf_map_do_batch	2020-02-19 16:01:25 -08:00
helpers.c	bpf: Add BPF_FUNC_jiffies64	2020-01-22 16:30:10 -08:00
inode.c	Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2020-02-08 13:26:41 -08:00
local_storage.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net	2019-12-22 09:54:33 -08:00
lpm_trie.c
Makefile	bpf: Introduce BPF_PROG_TYPE_STRUCT_OPS	2020-01-09 08:46:18 -08:00
map_in_map.c	bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS	2020-01-09 08:46:18 -08:00
map_in_map.h
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
percpu_freelist.h
queue_stack_maps.c
reuseport_array.c
stackmap.c	Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-12-03 09:29:50 -08:00
syscall.c	bpf: Introduce dynamic program extensions	2020-01-22 23:04:52 +01:00
sysfs_btf.c
tnum.c	bpf: Fix incorrect verifier simulation of ARSH under ALU32	2020-01-15 13:39:59 -08:00
trampoline.c	bpf: Allow to resolve bpf trampoline and dispatcher in unwind	2020-01-25 07:12:40 -08:00
verifier.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next	2020-01-23 08:10:16 +01:00
xskmap.c	xsk: Make xskmap flush_list common for all map instances	2019-12-19 21:09:43 -08:00