CVE-2026-31607usbip: validate number_of_packets in usbip_pack_ret_submit()

Official description

In the Linux kernel, the following vulnerability has been resolved: usbip: validate number_of_packets in usbip_pack_ret_submit() When a USB/IP client receives a RET_SUBMIT response, usbip_pack_ret_submit() unconditionally overwrites urb->number_of_packets from the network PDU. This value is subsequently used as the loop bound in usbip_recv_iso() and usbip_pad_iso() to iterate over urb->iso_frame_desc[], a flexible array whose size was fixed at URB allocation time based on the *original* number_of_packets from the CMD_SUBMIT. A malicious USB/IP server can set number_of_packets in the response to a value larger than what was originally submitted, causing a heap out-of-bounds write when usbip_recv_iso() writes to urb->iso_frame_desc[i] beyond the allocated region. KASAN confirmed this with kernel 7.0.0-rc5: BUG: KASAN: slab-out-of-bounds in usbip_recv_iso+0x46a/0x640 Write of size 4 at addr ffff888106351d40 by task vhci_rx/69 The buggy address is located 0 bytes to the right of allocated 320-byte region [ffff888106351c00, ffff888106351d40) The server side (stub_rx.c) and gadget side (vudc_rx.c) already validate number_of_packets in the CMD_SUBMIT path since commits c6688ef9f297 ("usbip: fix stub_rx: harden CMD_SUBMIT path to handle malicious input") and b78d830f0049 ("usbip: fix vudc_rx: harden CMD_SUBMIT path to handle malicious input"). The server side validates against USBIP_MAX_ISO_PACKETS because no URB exists yet at that point. On the client side we have the original URB, so we can use the tighter bound: the response must not exceed the original number_of_packets. This mirrors the existing validation of actual_length against transfer_buffer_length in usbip_recv_xbuff(), which checks the response value against the original allocation size. Kelvin Mbogo's series ("usb: usbip: fix integer overflow in usbip_recv_iso()", v2) hardens the receive-side functions themselves; this patch complements that work by catching the bad value at its source -- in usbip_pack_ret_submit() before the overwrite -- and using the tighter per-URB allocation bound rather than the global USBIP_MAX_ISO_PACKETS limit. Fix this by checking rpdu->number_of_packets against urb->number_of_packets in usbip_pack_ret_submit() before the overwrite. On violation, clamp to zero so that usbip_recv_iso() and usbip_pad_iso() safely return early.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/324262c38438255bf6bdbf6342ca47c0badaab76
• https://git.kernel.org/stable/c/973f2c250289f5bf6cc146b98aa6fdde11fe50d6
• https://git.kernel.org/stable/c/ce744264b06b97069b3722511ab355738311fee0
• https://git.kernel.org/stable/c/885c8591784da6314f9aa82fa460ac69f9f79e5f
• https://git.kernel.org/stable/c/8d155e2d1c4102f74f82a2bf9c016164bb0f7384
• https://git.kernel.org/stable/c/906f16a836de13fe61f49cdce2f66f2dbd14caf4
• https://git.kernel.org/stable/c/ef8ebb1c637b4cfb61a9dd2e013376774ee2033b
• https://git.kernel.org/stable/c/5e1c4ece08ccdc197177631f111845a2c68eede3
• https://git.kernel.org/stable/c/2ab833a16a825373aad2ba7d54b572b277e95b71
• https://access.redhat.com/security/cve/CVE-2026-31607 vdb-entry, x_refsource_REDHAT
• RHBZ#2461521 issue-tracking, x_refsource_REDHAT
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31607.json x_sadp-csaf-vex
• https://access.redhat.com/errata/RHSA-2026:25095 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:41236 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:24343 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:19569 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:23224 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:19568 vendor-advisory, x_refsource_REDHAT