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8f993d30b9
The block_len read from the host-supplied NTB header is checked against ntb_max but has no lower bound. When block_len is smaller than opts->ndp_size, the bounds check of: ndp_index > (block_len - opts->ndp_size) will underflow producing a huge unsigned value that ndp_index can never exceed, defeating the check entirely. The same underflow occurs in the datagram index checks against block_len - opts->dpe_size. With those checks neutered, a malicious USB host can choose ndp_index and datagram offsets that point past the actual transfer, and the skb_put_data() copies adjacent kernel memory into the network skb. Fix this by rejecting block lengths that cannot hold at least the NTB header plus one NDP. This will make block_len - opts->ndp_size and block_len - opts->dpe_size both well-defined. Commit8d2b1a1ec9("CDC-NCM: avoid overflow in sanity checking") fixed a related class of issues on the host side of NCM. Fixes:2b74b0a04d("USB: gadget: f_ncm: add bounds checks to ncm_unwrap_ntb()") Cc: stable <stable@kernel.org> Assisted-by: gregkh_clanker_t1000 Link: https://patch.msgid.link/2026040753-baffle-handheld-624d@gregkh Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>