[PATCH 5.4 61/88] net, neigh: clear whole pneigh_entry at alloc time

Greg Kroah-Hartman
2021-12-13T10:00:35Z

From: Eric Dumazet <edumazet@google.com>

commit e195e9b5dee6459d8c8e6a314cc71a644a0537fd upstream.

Commit 2c611ad97a82 ("net, neigh: Extend neigh->flags to 32 bit
to allow for extensions") enables a new KMSAM warning [1]

I think the bug is actually older, because the following intruction
only occurred if ndm->ndm_flags had NTF_PROXY set.

pn->flags = ndm->ndm_flags;

Let's clear all pneigh_entry fields at alloc time.

[1]
BUG: KMSAN: uninit-value in pneigh_fill_info+0x986/0xb30 net/core/neighbour.c:2593
pneigh_fill_info+0x986/0xb30 net/core/neighbour.c:2593
pneigh_dump_table net/core/neighbour.c:2715 [inline]
neigh_dump_info+0x1e3f/0x2c60 net/core/neighbour.c:2832
netlink_dump+0xaca/0x16a0 net/netlink/af_netlink.c:2265
__netlink_dump_start+0xd1c/0xee0 net/netlink/af_netlink.c:2370
netlink_dump_start include/linux/netlink.h:254 [inline]
rtnetlink_rcv_msg+0x181b/0x18c0 net/core/rtnetlink.c:5534
netlink_rcv_skb+0x447/0x800 net/netlink/af_netlink.c:2491
rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5589
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x1095/0x1360 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x16f3/0x1870 net/netlink/af_netlink.c:1916
sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg net/socket.c:724 [inline]
sock_write_iter+0x594/0x690 net/socket.c:1057
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write fs/read_write.c:503 [inline]
vfs_write+0x1318/0x2030 fs/read_write.c:590
ksys_write+0x28c/0x520 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0xdb/0x120 fs/read_write.c:652
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
slab_post_alloc_hook mm/slab.h:524 [inline]
slab_alloc_node mm/slub.c:3251 [inline]
slab_alloc mm/slub.c:3259 [inline]
__kmalloc+0xc3c/0x12d0 mm/slub.c:4437
kmalloc include/linux/slab.h:595 [inline]
pneigh_lookup+0x60f/0xd70 net/core/neighbour.c:766
arp_req_set_public net/ipv4/arp.c:1016 [inline]
arp_req_set+0x430/0x10a0 net/ipv4/arp.c:1032
arp_ioctl+0x8d4/0xb60 net/ipv4/arp.c:1232
inet_ioctl+0x4ef/0x820 net/ipv4/af_inet.c:947
sock_do_ioctl net/socket.c:1118 [inline]
sock_ioctl+0xa3f/0x13e0 net/socket.c:1235
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0x2df/0x4a0 fs/ioctl.c:860
__x64_sys_ioctl+0xd8/0x110 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x44/0xae

CPU: 1 PID: 20001 Comm: syz-executor.0 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Fixes: 62dd93181aaa ("[IPV6] NDISC: Set per-entry is_router flag in Proxy NA.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Roopa Prabhu <roopa@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20211206165329.1049835-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/neighbour.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -734,11 +734,10 @@ struct pneigh_entry * pneigh_lookup(stru

ASSERT_RTNL();

- n = kmalloc(sizeof(*n) + key_len, GFP_KERNEL);
+ n = kzalloc(sizeof(*n) + key_len, GFP_KERNEL);
if (!n)
goto out;

- n->protocol = 0;
write_pnet(&n->net, net);
memcpy(n->key, pkey, key_len);
n->dev = dev;