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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-ORIG-GUID: csHy_1MDKRMt7vIiub5CibLf9PU-gsM7 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTE1MDA2NiBTYWx0ZWRfX0Rzbksz1Bzw8 jfOysOYUuVoRGHSglg7v50IEU1o4qLEZd/9+bSL0H966f15ESE3bB4qo7ByapgJ6vbIKNRKq4Ul oVBOoMvkeBpTJ7Xam4sDThdjEU3E5pc= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTE1MDA2NiBTYWx0ZWRfX/9C3Sd7woIMa 89+d7dzHmzvRDQ/8+9GROjuFFhPVB0/vpxmvX7XbSoC1K6oIdE3z/mtUAjdZ7syK92KRh0m+kR2 WAZJYDbmVJVNtvGFK8OwG9B6jiJTS8pdEXEnUioobonkaDOFRMJwcLh61mgYJNKdMT9xRDqPQG0 G4VQqrnoyyoMSvEXdLzdLBAtPJwYW3eY04nDu5ACX2Dbx8D+43xuvHFFK7gcQQxcIFF0okJSM0r OSzCmb3aeFFvDuZHSaNWpIeEN5Uxqoz3nWT0tZFXG56AzV1CJfd8JEy1IfBGUQt3IcYy7vqJciB Ab9837FdGVXK9hcdvKk/6vLn6EM1ErTpfAdYpNhBnXIkO3wLivKuQaR+f5TEyzb7KkQN8ZwuGgh Mp7DGi8N7YjySJH2khZLybIrAanRux8qcSy+fzQ5wexIybHU5jfpQ5Py0iuSRfhmBe52Mxh/j+X 3iwuz0s1v/kgcnQeZ4Q== X-Authority-Analysis: v=2.4 cv=XKel2ghE c=1 sm=1 tr=0 ts=6aa8cf42 cx=c_pps a=oF/VQ+ItUULfLr/lQ2/icg==:117 a=ebQaAufLtzKgtO4u2lSP0Q==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yx91gb_oNiZeI1HMLzn7:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=HSZgmaD_RsK9m5tnku4A:9 a=QEXdDO2ut3YA:10 a=3WC7DwWrALyhR5TkjVHa:22 X-Proofpoint-GUID: csHy_1MDKRMt7vIiub5CibLf9PU-gsM7 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-15_01,2026-09-14_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 spamscore=0 bulkscore=0 phishscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1015 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609150066 On 9/15/2026 9:41 AM, Aldo Ariel Panzardo wrote: > The next-NDP pointers form a chain supplied by the USB host. A cyclic > chain therefore makes the receive path loop indefinitely and repeatedly > allocate datagram skbs. > Is this an issue with NTB creation on host side ? (seems like it). If so, can you update commit message with an example packet details indicating the same (or a walkthrough of a packet with such headers indicating a cyclic chain). Regards, Krishna, > Prewalk the chain using only bounded header reads before parsing any > NDP. NDP offsets must be four-byte aligned, so following more than > block_len / 4 valid offsets proves that the chain contains a cycle. > This terminates cyclic chains without imposing an arbitrary limit on > valid NTBs or allocating skbs before the chain is known to terminate. > > Fixes: 370af734dfaf ("usb: gadget: NCM: RX function support multiple NDPs") > Cc: stable@vger.kernel.org > Signed-off-by: Aldo Ariel Panzardo > --- > drivers/usb/gadget/function/f_ncm.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c > index 64eabda2f5..085aea142f 100644 > --- a/drivers/usb/gadget/function/f_ncm.c > +++ b/drivers/usb/gadget/function/f_ncm.c > @@ -1175,6 +1175,7 @@ static int ncm_unwrap_ntb(struct gether *port, > unsigned dg_len, dg_len2; > unsigned ndp_len; > unsigned block_len; > + unsigned int ndp_count, next_ndp_index; > struct sk_buff *skb2; > int ret = -EINVAL; > unsigned ntb_max = le32_to_cpu(ntb_parameters.dwNtbOutMaxSize); > @@ -1224,6 +1225,30 @@ static int ncm_unwrap_ntb(struct gether *port, > } > > ndp_index = get_ncm(&tmp, opts->ndp_index); > + next_ndp_index = ndp_index; > + ndp_count = 0; > + > + /* Validate the NDP chain before allocating datagram skbs. */ > + while (next_ndp_index) { > + if (next_ndp_index % 4 || > + next_ndp_index < opts->nth_size || > + next_ndp_index > block_len - opts->ndp_size) { > + INFO(port->func.config->cdev, "Bad index: %#X\n", > + next_ndp_index); > + goto err; > + } > + > + /* More aligned offsets than fit in the NTB imply a cycle. */ > + if (++ndp_count > block_len / 4) { > + INFO(port->func.config->cdev, "NDP chain cycle\n"); > + goto err; > + } > + > + tmp = (__le16 *)(ntb_ptr + next_ndp_index); > + tmp += 3; /* skip the signature and length */ > + tmp += opts->reserved1; > + next_ndp_index = get_ncm(&tmp, opts->next_ndp_index); > + } > > /* Run through all the NDP's in the NTB */ > do {