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Date: Mon, 2 Nov 2020 03:41:00 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>
Cc: "David S . Miller" <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
bpf <bpf@...r.kernel.org>, syzbot <syzkaller@...glegroups.com>,
Song Liu <songliubraving@...com>
Subject: [PATCH bpf-net] bpf: fix error path in htab_map_alloc()
From: Eric Dumazet <edumazet@...gle.com>
syzbot was able to trigger a use-after-free in htab_map_alloc() [1]
htab_map_alloc() lacks a call to lockdep_unregister_key() in its error path.
lockdep_register_key() and lockdep_unregister_key() can not fail,
it seems better to use them right after htab allocation and before
htab freeing, avoiding more goto/labels in htab_map_alloc()
[1]
BUG: KASAN: use-after-free in lockdep_register_key+0x356/0x3e0 kernel/locking/lockdep.c:1182
Read of size 8 at addr ffff88805fa67ad8 by task syz-executor.3/2356
CPU: 1 PID: 2356 Comm: syz-executor.3 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x4c8 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
lockdep_register_key+0x356/0x3e0 kernel/locking/lockdep.c:1182
htab_init_buckets kernel/bpf/hashtab.c:144 [inline]
htab_map_alloc+0x6c5/0x14a0 kernel/bpf/hashtab.c:521
find_and_alloc_map kernel/bpf/syscall.c:122 [inline]
map_create kernel/bpf/syscall.c:825 [inline]
__do_sys_bpf+0xa80/0x5180 kernel/bpf/syscall.c:4381
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45deb9
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0eafee1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000001a00 RCX: 000000000045deb9
RDX: 0000000000000040 RSI: 0000000020000040 RDI: 405a020000000000
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffd3cf9eabf R14: 00007f0eafee29c0 R15: 000000000118bf2c
Allocated by task 2053:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:461
kmalloc include/linux/slab.h:554 [inline]
kzalloc include/linux/slab.h:666 [inline]
htab_map_alloc+0xdf/0x14a0 kernel/bpf/hashtab.c:454
find_and_alloc_map kernel/bpf/syscall.c:122 [inline]
map_create kernel/bpf/syscall.c:825 [inline]
__do_sys_bpf+0xa80/0x5180 kernel/bpf/syscall.c:4381
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 2053:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0x102/0x140 mm/kasan/common.c:422
slab_free_hook mm/slub.c:1544 [inline]
slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1577
slab_free mm/slub.c:3142 [inline]
kfree+0xdb/0x360 mm/slub.c:4124
htab_map_alloc+0x3f9/0x14a0 kernel/bpf/hashtab.c:549
find_and_alloc_map kernel/bpf/syscall.c:122 [inline]
map_create kernel/bpf/syscall.c:825 [inline]
__do_sys_bpf+0xa80/0x5180 kernel/bpf/syscall.c:4381
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff88805fa67800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 728 bytes inside of
1024-byte region [ffff88805fa67800, ffff88805fa67c00)
The buggy address belongs to the page:
page:000000003c5582c4 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5fa60
head:000000003c5582c4 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 ffffea0000bc1200 0000000200000002 ffff888010041140
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88805fa67980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805fa67a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805fa67a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805fa67b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805fa67b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Fixes: c50eb518e262 ("bpf: Use separate lockdep class for each hashtab")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
Cc: Song Liu <songliubraving@...com>
---
kernel/bpf/hashtab.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index da59ba978d17230684276001dce1de8e7816cb12..23f73d4649c9c9eaf6246f1088ddfee2d3875ea9 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -141,7 +141,6 @@ static void htab_init_buckets(struct bpf_htab *htab)
{
unsigned i;
- lockdep_register_key(&htab->lockdep_key);
for (i = 0; i < htab->n_buckets; i++) {
INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
if (htab_use_raw_lock(htab)) {
@@ -455,6 +454,8 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
if (!htab)
return ERR_PTR(-ENOMEM);
+ lockdep_register_key(&htab->lockdep_key);
+
bpf_map_init_from_attr(&htab->map, attr);
if (percpu_lru) {
@@ -546,6 +547,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
free_charge:
bpf_map_charge_finish(&htab->map.memory);
free_htab:
+ lockdep_unregister_key(&htab->lockdep_key);
kfree(htab);
return ERR_PTR(err);
}
@@ -1364,9 +1366,9 @@ static void htab_map_free(struct bpf_map *map)
free_percpu(htab->extra_elems);
bpf_map_area_free(htab->buckets);
- lockdep_unregister_key(&htab->lockdep_key);
for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
free_percpu(htab->map_locked[i]);
+ lockdep_unregister_key(&htab->lockdep_key);
kfree(htab);
}
--
2.29.1.341.ge80a0c044ae-goog
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