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