Syzkaller reports the following failure:
BUG: KASAN: use-after-free in kref_put include/linux/kref.h:64 [inline]
BUG: KASAN: use-after-free in j1939_priv_put+0x25/0xa0 net/can/j1939/main.c:172
Write of size 4 at addr ffff888141c15058 by task swapper/3/0
CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.10.144-syzkaller #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x167 lib/dump_stack.c:118
print_address_description.constprop.0+0x1c/0x220 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
check_memory_region_inline mm/kasan/generic.c:186 [inline]
check_memory_region+0x145/0x190 mm/kasan/generic.c:192
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
__refcount_sub_and_test include/linux/refcount.h:272 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
kref_put include/linux/kref.h:64 [inline]
j1939_priv_put+0x25/0xa0 net/can/j1939/main.c:172
j1939_sk_sock_destruct+0x44/0x90 net/can/j1939/socket.c:374
__sk_destruct+0x4e/0x820 net/core/sock.c:1784
rcu_do_batch kernel/rcu/tree.c:2485 [inline]
rcu_core+0xb35/0x1a30 kernel/rcu/tree.c:2726
__do_softirq+0x289/0x9a3 kernel/softirq.c:298
asm_call_irq_on_stack+0x12/0x20
</IRQ>
__run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
do_softirq_own_stack+0xaa/0xe0 arch/x86/kernel/irq_64.c:77
invoke_softirq kernel/softirq.c:393 [inline]
__irq_exit_rcu kernel/softirq.c:423 [inline]
irq_exit_rcu+0x136/0x200 kernel/softirq.c:435
sysvec_apic_timer_interrupt+0x4d/0x100 arch/x86/kernel/apic/apic.c:1095
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635
Allocated by task 1141:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc9/0xd0 mm/kasan/common.c:461
kmalloc include/linux/slab.h:552 [inline]
kzalloc include/linux/slab.h:664 [inline]
j1939_priv_create net/can/j1939/main.c:131 [inline]
j1939_netdev_start+0x111/0x860 net/can/j1939/main.c:268
j1939_sk_bind+0x8ea/0xd30 net/can/j1939/socket.c:485
__sys_bind+0x1f2/0x260 net/socket.c:1645
__do_sys_bind net/socket.c:1656 [inline]
__se_sys_bind net/socket.c:1654 [inline]
__x64_sys_bind+0x6f/0xb0 net/socket.c:1654
do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xc6
Freed by task 1141:
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+0x112/0x170 mm/kasan/common.c:422
slab_free_hook mm/slub.c:1542 [inline]
slab_free_freelist_hook+0xad/0x190 mm/slub.c:1576
slab_free mm/slub.c:3149 [inline]
kfree+0xd9/0x3b0 mm/slub.c:4125
j1939_netdev_start+0x5ee/0x860 net/can/j1939/main.c:300
j1939_sk_bind+0x8ea/0xd30 net/can/j1939/socket.c:485
__sys_bind+0x1f2/0x260 net/socket.c:1645
__do_sys_bind net/socket.c:1656 [inline]
__se_sys_bind net/socket.c:1654 [inline]
__x64_sys_bind+0x6f/0xb0 net/socket.c:1654
do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xc6
It can be caused by this scenario:
CPU0 CPU1
j1939_sk_bind(socket0, ndev0, ...)
j1939_netdev_start()
j1939_sk_bind(socket1, ndev0, ...)
j1939_netdev_start()
mutex_lock(&j1939_netdev_lock)
j1939_priv_set(ndev0, priv)
mutex_unlock(&j1939_netdev_lock)
if (priv_new)
kref_get(&priv_new->rx_kref)
return priv_new;
/* inside j1939_sk_bind() */
jsk->priv = priv
j1939_can_rx_register(priv) // fails
j1939_priv_set(ndev, NULL)
kfree(priv)
j1939_sk_sock_destruct()
j1939_priv_put() // <- uaf
To avoid this, call j1939_can_rx_register() under j1939_netdev_lock so
that a concurrent thread cannot process j1939_priv before
j1939_can_rx_register() returns.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Fedor Pchelkin <pchelkin at ispras.ru>
---
net/can/j1939/main.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index 6ed79afe19a5..ecff1c947d68 100644
--- a/net/can/j1939/main.c
+++ b/net/can/j1939/main.c
@@ -290,16 +290,18 @@ struct j1939_priv *j1939_netdev_start(struct net_device *ndev)
return priv_new;
}
j1939_priv_set(ndev, priv);
- mutex_unlock(&j1939_netdev_lock);
ret = j1939_can_rx_register(priv);
if (ret < 0)
goto out_priv_put;
+ mutex_unlock(&j1939_netdev_lock);
return priv;
out_priv_put:
j1939_priv_set(ndev, NULL);
+ mutex_unlock(&j1939_netdev_lock);
+
dev_put(ndev);
kfree(priv);
--
2.34.1