Re: [PATCH net v3] net: nfc: nci: Add parameter validation for packet data

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 19/09/2025 07:45, Deepak Sharma wrote:
> Syzbot reported an uninit-value bug at nci_init_req for commit
> 5aca7966d2a7 ("Merge tag 'perf-tools-fixes-for-v6.17-2025-09-16'..).
> 
> This bug arises due to very limited and poor input validation
> that was done at nic_valid_size(). This validation only
> validates the skb->len (directly reflects size provided at the
> userspace interface) with the length provided in the buffer
> itself (interpreted as NCI_HEADER). This leads to the processing
> of memory content at the address assuming the correct layout
> per what opcode requires there. This leads to the accesses to
> buffer of `skb_buff->data` which is not assigned anything yet.
> 
> Following the same silent drop of packets of invalid sizes at
> `nic_valid_size()`, add validation of the data in the respective
> handlers and return error values in case of failure. Release
> the skb if error values are returned from handlers in
> `nci_nft_packet` and effectively do a silent drop
> 
> Possible TODO: because we silently drop the packets, the
> call to `nci_request` will be waiting for completion of request
> and will face timeouts. These timeouts can get excessively logged
> in the dmesg. A proper handling of them may require to export
> `nci_request_cancel` (or propagate error handling from the
> nft packets handlers).
> 
> Reported-by: syzbot+740e04c2a93467a0f8c8@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=740e04c2a93467a0f8c8
> Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation)
> Tested-by: syzbot+740e04c2a93467a0f8c8@syzkaller.appspotmail.com
> Signed-off-by: Deepak Sharma <deepak.sharma.472935@gmail.com>
> ---
> v3:
>   - Move the checks inside the packet data handlers
>   - Improvements to the commit message
> 
> v2:
>   - Fix the release of skb in case of the early return
> 
> v1:
>   - Add checks in `nci_ntf_packet` on the skb->len and do early return
>     on failure
> 

LGTM,
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>