[PATCH 4.12 16/99] tun: handle register_netdevice() failures properly

Greg Kroah-Hartman
2017-08-28T09:23:52Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit ff244c6b29b176f3f448bc75e55df297225e1b3a ]

syzkaller reported a double free [1], caused by the fact
that tun driver was not updated properly when priv_destructor
was added.

When/if register_netdevice() fails, priv_destructor() must have been
called already.

[1]
BUG: KASAN: double-free or invalid-free in selinux_tun_dev_free_security+0x15/0x20 security/selinux/hooks.c:5023

CPU: 0 PID: 2919 Comm: syzkaller227220 Not tainted 4.13.0-rc4+ #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:52
print_address_description+0x7f/0x260 mm/kasan/report.c:252
kasan_report_double_free+0x55/0x80 mm/kasan/report.c:333
kasan_slab_free+0xa0/0xc0 mm/kasan/kasan.c:514
__cache_free mm/slab.c:3503 [inline]
kfree+0xd3/0x260 mm/slab.c:3820
selinux_tun_dev_free_security+0x15/0x20 security/selinux/hooks.c:5023
security_tun_dev_free_security+0x48/0x80 security/security.c:1512
tun_set_iff drivers/net/tun.c:1884 [inline]
__tun_chr_ioctl+0x2ce6/0x3d50 drivers/net/tun.c:2064
tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2309
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x443ff9
RSP: 002b:00007ffc34271f68 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000443ff9
RDX: 0000000020533000 RSI: 00000000400454ca RDI: 0000000000000003
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000401ce0
R13: 0000000000401d70 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 2919:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:551
kmem_cache_alloc_trace+0x101/0x6f0 mm/slab.c:3627
kmalloc include/linux/slab.h:493 [inline]
kzalloc include/linux/slab.h:666 [inline]
selinux_tun_dev_alloc_security+0x49/0x170 security/selinux/hooks.c:5012
security_tun_dev_alloc_security+0x6d/0xa0 security/security.c:1506
tun_set_iff drivers/net/tun.c:1839 [inline]
__tun_chr_ioctl+0x1730/0x3d50 drivers/net/tun.c:2064
tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2309
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 2919:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x6e/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3503 [inline]
kfree+0xd3/0x260 mm/slab.c:3820
selinux_tun_dev_free_security+0x15/0x20 security/selinux/hooks.c:5023
security_tun_dev_free_security+0x48/0x80 security/security.c:1512
tun_free_netdev+0x13b/0x1b0 drivers/net/tun.c:1563
register_netdevice+0x8d0/0xee0 net/core/dev.c:7605
tun_set_iff drivers/net/tun.c:1859 [inline]
__tun_chr_ioctl+0x1caf/0x3d50 drivers/net/tun.c:2064
tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2309
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801d2843b40
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
32-byte region [ffff8801d2843b40, ffff8801d2843b60)
The buggy address belongs to the page:
page:ffffea000660cea8 count:1 mapcount:0 mapping:ffff8801d2843000 index:0xffff8801d2843fc1
flags: 0x200000000000100(slab)
raw: 0200000000000100 ffff8801d2843000 ffff8801d2843fc1 000000010000003f
raw: ffffea0006626a40 ffffea00066141a0 ffff8801dbc00100
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d2843a00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8801d2843a80: 00 00 00 fc fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8801d2843b00: 00 00 00 00 fc fc fc fc fb fb fb fb fc fc fc fc
^
ffff8801d2843b80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8801d2843c00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc

==================================================================

Fixes: cf124db566e6 ("net: Fix inconsistent teardown and release of private netdev state.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/tun.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1876,6 +1876,9 @@ static int tun_set_iff(struct net *net,

err_detach:
tun_detach_all(dev);
+ /* register_netdevice() already called tun_free_netdev() */
+ goto err_free_dev;
+
err_free_flow:
tun_flow_uninit(tun);
security_tun_dev_free_security(tun->security);