Re: [PATCH net] nfc: nci: Fix uninit-value in nci_dev_up

[Krzysztof Kozlowski]

On 12/03/2024 15:56, Ryosuke Yasuoka wrote:
> syzbot reported the following unitit-value access issue [1]:

If there is going to be any new version then: typo, uninit-value
> 
> nci_ntf_packet() calls each ntf operation parsed from skb->data. When
> the payload length is zero, each operation handler reads uninitialized
> payload and KMSAN detects this issue. Such notification packet should be
> silently discarded since it is unexpected for any notification handlers.
> 
> This patch resolved this issue by checking payload size before calling
> each notification handler codes.
> 
> BUG: KMSAN: uninit-value in nci_init_req net/nfc/nci/core.c:177 [inline]
> BUG: KMSAN: uninit-value in __nci_request net/nfc/nci/core.c:108 [inline]
> BUG: KMSAN: uninit-value in nci_open_device net/nfc/nci/core.c:521 [inline]
> BUG: KMSAN: uninit-value in nci_dev_up+0xfec/0x1b10 net/nfc/nci/core.c:632
>  nci_init_req net/nfc/nci/core.c:177 [inline]
>  __nci_request net/nfc/nci/core.c:108 [inline]
>  nci_open_device net/nfc/nci/core.c:521 [inline]
>  nci_dev_up+0xfec/0x1b10 net/nfc/nci/core.c:632
>  nfc_dev_up+0x26e/0x440 net/nfc/core.c:118
>  nfc_genl_dev_up+0xfe/0x1d0 net/nfc/netlink.c:770
>  genl_family_rcv_msg_doit net/netlink/genetlink.c:972 [inline]
>  genl_family_rcv_msg net/netlink/genetlink.c:1052 [inline]
>  genl_rcv_msg+0x11ec/0x1290 net/netlink/genetlink.c:1067
>  netlink_rcv_skb+0x371/0x650 net/netlink/af_netlink.c:2545
>  genl_rcv+0x40/0x60 net/netlink/genetlink.c:1076
>  netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]
>  netlink_unicast+0xf47/0x1250 net/netlink/af_netlink.c:1368
>  netlink_sendmsg+0x1238/0x13d0 net/netlink/af_netlink.c:1910
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  __sock_sendmsg net/socket.c:745 [inline]
>  ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
>  ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
>  __sys_sendmsg net/socket.c:2667 [inline]
>  __do_sys_sendmsg net/socket.c:2676 [inline]
>  __se_sys_sendmsg net/socket.c:2674 [inline]
>  __x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> 
> Uninit was stored to memory at:
>  nci_core_reset_ntf_packet net/nfc/nci/ntf.c:36 [inline]
>  nci_ntf_packet+0x19dc/0x39c0 net/nfc/nci/ntf.c:782
>  nci_rx_work+0x213/0x500 net/nfc/nci/core.c:1522
>  process_one_work kernel/workqueue.c:2633 [inline]
>  process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2706
>  worker_thread+0xf45/0x1490 kernel/workqueue.c:2787
>  kthread+0x3ed/0x540 kernel/kthread.c:388
>  ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
> 
> Uninit was created at:
>  slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
>  slab_alloc_node mm/slub.c:3478 [inline]
>  kmem_cache_alloc_node+0x5e9/0xb10 mm/slub.c:3523
>  kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
>  __alloc_skb+0x318/0x740 net/core/skbuff.c:651
>  alloc_skb include/linux/skbuff.h:1286 [inline]
>  virtual_ncidev_write+0x6d/0x280 drivers/nfc/virtual_ncidev.c:120
>  vfs_write+0x48b/0x1200 fs/read_write.c:588
>  ksys_write+0x20f/0x4c0 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+0x93/0xd0 fs/read_write.c:652
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> 
> CPU: 1 PID: 5012 Comm: syz-executor935 Not tainted 6.7.0-syzkaller-00562-g9f8413c4a66f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023

These two lines are not really relevant, it's a virtual platform, so
whether this is Google or Amazon it does not matter, and your log paste
is already quite long. If there is going to be any resend, I propose to
drop.

> 
> Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
> Reported-and-tested-by: syzbot+7ea9413ea6749baf5574@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=7ea9413ea6749baf5574 [1]
> Signed-off-by: Ryosuke Yasuoka <ryasuoka@xxxxxxxxxx>
> ---
>  net/nfc/nci/ntf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
> index 994a0a1efb58..56624387e253 100644
> --- a/net/nfc/nci/ntf.c
> +++ b/net/nfc/nci/ntf.c
> @@ -765,6 +765,9 @@ void nci_ntf_packet(struct nci_dev *ndev, struct sk_buff *skb)
>  		 nci_opcode_oid(ntf_opcode),
>  		 nci_plen(skb->data));
>  
> +	if (!nci_plen(skb->data))
> +		goto end;

Looks reasonable, however wouldn't there be the same issue in
nci_rsp_packet() and other cases from nci_rx_work()? I wonder why only
NTF packets could be constructed without payload.

Best regards,
Krzysztof