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Subject[PATCH AUTOSEL 4.14 104/105] gtp: fix use-after-free in gtp_newlink()
Date
From: Taehee Yoo <ap420073@gmail.com>

[ Upstream commit a2bed90704c68d3763bf24decb1b781a45395de8 ]

Current gtp_newlink() could be called after unregister_pernet_subsys().
gtp_newlink() uses gtp_net but it can be destroyed by
unregister_pernet_subsys().
So unregister_pernet_subsys() should be called after
rtnl_link_unregister().

Test commands:
#SHELL 1
while :
do
for i in {1..5}
do
./gtp-link add gtp$i &
done
killall gtp-link
done

#SHELL 2
while :
do
modprobe -rv gtp
done

Splat looks like:
[ 753.176631] BUG: KASAN: use-after-free in gtp_newlink+0x9b4/0xa5c [gtp]
[ 753.177722] Read of size 8 at addr ffff8880d48f2458 by task gtp-link/7126
[ 753.179082] CPU: 0 PID: 7126 Comm: gtp-link Tainted: G W 5.2.0-rc6+ #50
[ 753.185801] Call Trace:
[ 753.186264] dump_stack+0x7c/0xbb
[ 753.186863] ? gtp_newlink+0x9b4/0xa5c [gtp]
[ 753.187583] print_address_description+0xc7/0x240
[ 753.188382] ? gtp_newlink+0x9b4/0xa5c [gtp]
[ 753.189097] ? gtp_newlink+0x9b4/0xa5c [gtp]
[ 753.189846] __kasan_report+0x12a/0x16f
[ 753.190542] ? gtp_newlink+0x9b4/0xa5c [gtp]
[ 753.191298] kasan_report+0xe/0x20
[ 753.191893] gtp_newlink+0x9b4/0xa5c [gtp]
[ 753.192580] ? __netlink_ns_capable+0xc3/0xf0
[ 753.193370] __rtnl_newlink+0xb9f/0x11b0
[ ... ]
[ 753.241201] Allocated by task 7186:
[ 753.241844] save_stack+0x19/0x80
[ 753.242399] __kasan_kmalloc.constprop.3+0xa0/0xd0
[ 753.243192] __kmalloc+0x13e/0x300
[ 753.243764] ops_init+0xd6/0x350
[ 753.244314] register_pernet_operations+0x249/0x6f0
[ ... ]
[ 753.251770] Freed by task 7178:
[ 753.252288] save_stack+0x19/0x80
[ 753.252833] __kasan_slab_free+0x111/0x150
[ 753.253962] kfree+0xc7/0x280
[ 753.254509] ops_free_list.part.11+0x1c4/0x2d0
[ 753.255241] unregister_pernet_operations+0x262/0x390
[ ... ]
[ 753.285883] list_add corruption. next->prev should be prev (ffff8880d48f2458), but was ffff8880d497d878. (next.
[ 753.287241] ------------[ cut here ]------------
[ 753.287794] kernel BUG at lib/list_debug.c:25!
[ 753.288364] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[ 753.289099] CPU: 0 PID: 7126 Comm: gtp-link Tainted: G B W 5.2.0-rc6+ #50
[ 753.291036] RIP: 0010:__list_add_valid+0x74/0xd0
[ 753.291589] Code: 48 39 da 75 27 48 39 f5 74 36 48 39 dd 74 31 48 83 c4 08 b8 01 00 00 00 5b 5d c3 48 89 d9 48b
[ 753.293779] RSP: 0018:ffff8880cae8f398 EFLAGS: 00010286
[ 753.294401] RAX: 0000000000000075 RBX: ffff8880d497d878 RCX: 0000000000000000
[ 753.296260] RDX: 0000000000000075 RSI: 0000000000000008 RDI: ffffed10195d1e69
[ 753.297070] RBP: ffff8880cd250ae0 R08: ffffed101b4bff21 R09: ffffed101b4bff21
[ 753.297899] R10: 0000000000000001 R11: ffffed101b4bff20 R12: ffff8880d497d878
[ 753.298703] R13: 0000000000000000 R14: ffff8880cd250ae0 R15: ffff8880d48f2458
[ 753.299564] FS: 00007f5f79805740(0000) GS:ffff8880da400000(0000) knlGS:0000000000000000
[ 753.300533] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 753.301231] CR2: 00007fe8c7ef4f10 CR3: 00000000b71a6006 CR4: 00000000000606f0
[ 753.302183] Call Trace:
[ 753.302530] gtp_newlink+0x5f6/0xa5c [gtp]
[ 753.303037] ? __netlink_ns_capable+0xc3/0xf0
[ 753.303576] __rtnl_newlink+0xb9f/0x11b0
[ 753.304092] ? rtnl_link_unregister+0x230/0x230

Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/gtp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 53fd66534e3a..5de4053774b8 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1383,9 +1383,9 @@ late_initcall(gtp_init);

static void __exit gtp_fini(void)
{
- unregister_pernet_subsys(&gtp_net_ops);
genl_unregister_family(&gtp_genl_family);
rtnl_link_unregister(&gtp_link_ops);
+ unregister_pernet_subsys(&gtp_net_ops);

pr_info("GTP module unloaded\n");
}
--
2.20.1
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