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Fix transfer lengths that wrap when narrowed to 16 bits - #3968
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Organization UI Review profile: QUIET Plan: Advanced Run ID: 📒 Files selected for processing (2)
Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 7 remain after this review. 📝 WalkthroughWalkthroughThe vendor buffered transmit path forwards the full MSC device validation rejects READ10 and WRITE10 commands with zero blocks or block sizes above the 16-bit range. The MSC host splits data transfers into chunks of up to Sequence Diagram(s)sequenceDiagram
participant MSCHost
participant USBHost
MSCHost->>USBHost: Submit data chunk up to 0xFC00 bytes
USBHost-->>MSCHost: Return transfer result and byte count
MSCHost->>USBHost: Submit another chunk after a successful full chunk when bytes remain
MSCHost->>USBHost: Queue CSW when the data stage ends
Priority: ➖ Normal Merge Risk: 🟡 Moderate · up to An MSC command can remain pending if a later data chunk cannot be submitted. Handle that failure before merging unless the risk is explicitly accepted. Security Architecture ReviewSecurity architecture risk: 🟡 Moderate · up to Large USB mass-storage transfers now require several submissions. If a later submission fails, the command can remain incomplete without notifying the application. The impact is limited to that host command; no direct malicious trigger or broader compromise was established. Retained concerns
Security review detailsSecurity Blast Radius
Security Findings and Attack Paths
Trust Boundaries and Controls
Resilience and Maintainability Implications
Hardening Proposals
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches 💡 2📝 Generate docstrings 💡
🛠️ Fix failing CI checks 💡
🧪 Generate unit tests (beta)
✨ Simplify code
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Hardware-in-the-loop (HIL) Test Reporthfp-iar✅ 56 passed · ❌ 0 failed · ⚪ 0 skipped · blank not run
hfp.json✅ 56 passed · ❌ 0 failed · ⚪ 0 skipped · blank not run
tinyusb-esp.json✅ 28 passed · ❌ 4 failed · ⚪ 0 skipped · blank not run
tinyusb.json✅ 364 passed · ❌ 36 failed · ⚪ 17 skipped · blank not run
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| target | .text | .rodata | .data | .bss | total | % diff |
|---|---|---|---|---|---|---|
| frdm_kl25z/cdc_msc_hid | 28,332 → 28,476 (+144) | — | — | — | 28,492 → 28,636 (+144) | +0.5% |
| frdm_kl25z/msc_file_explorer | 35,360 → 35,524 (+164) | — | — | — | 35,520 → 35,684 (+164) | +0.5% |
| nanoch32v203/cdc_msc_hid | 32,480 → 32,640 (+160) | — | — | 5,316 → 5,332 (+16) | 40,476 → 40,652 (+176) | +0.4% |
| metro_m0_express/midi_test | 8,576 → 8,612 (+36) | — | — | — | 8,608 → 8,644 (+36) | +0.4% |
| ea4088_quickstart/cdc_msc_hid | 26,860 → 26,988 (+128) | — | — | 2,620 → 2,636 (+16) | 35,332 → 35,476 (+144) | +0.4% |
| metro_m0_express/cdc_msc_hid | 26,224 → 26,368 (+144) | — | — | 5,088 → 5,104 (+16) | 39,808 → 39,968 (+160) | +0.4% |
| metro_m0_express/printer_to_cdc | 9,500 → 9,536 (+36) | — | — | — | 9,528 → 9,564 (+36) | +0.4% |
| stm32g0b1nucleo/cdc_msc_hid | 32,176 → 32,316 (+140) | — | — | 5,336 → 5,352 (+16) | 41,364 → 41,520 (+156) | +0.4% |
| metro_m0_express/cdc_dual_ports | 9,524 → 9,560 (+36) | — | — | — | 9,556 → 9,592 (+36) | +0.4% |
| lpcxpresso11u68/midi_test | 9,244 → 9,280 (+36) | — | — | — | 9,668 → 9,704 (+36) | +0.4% |
tu_edpt_stream_write/read take a uint32_t bufsize but passed (uint16_t)bufsize to the fifo, so a 65536-byte request became 0 and 65537 became 1 and the transfer stalled. #2219 added this clamp in CDC; f11adb0 moved CDC onto the shared stream and dropped it. Clamp at the stream boundary so every stream user is covered, and let tud_vendor_n_write pass the full request through.
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tuh_msc_read10/write10 take a uint16_t block count, but the data stage was submitted as one usbh_edpt_xfer() of (uint16_t) total_bytes, so 128 sectors of 512 bytes became a 0-byte transfer and the command wedged. Submit the data stage in 0xFC00-byte pieces, a multiple of every bulk packet size, ending on a short or failed piece, and reject block counts whose byte total overflows the CBW field.
tuh_edpt_xfer() narrowed a uint32_t buflen, so 65536 queued a 0-byte transfer and returned success. tud_mtp_response_send() took the container length unchecked, wrapping above 64 KiB and reading past the endpoint buffer below that.
The host-computed block size was narrowed to uint16_t, so 66048 bytes for one block read as 512 and walked past the requested LBAs.
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Actionable comments posted: 1
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Inline comments:
In `@src/class/msc/msc_host.c`:
- Line 352: Update the `data_stage_xfer()` failure path in `msch_xfer_cb()` to
treat a failed chunk submission as a terminal command error and notify the
caller through `complete_cb`, rather than returning with `MSC_STAGE_DATA` still
active. Add a test that makes the second submission fail and verifies command
completion.
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📒 Files selected for processing (7)
src/class/msc/msc_device.csrc/class/msc/msc_host.csrc/class/mtp/mtp_device.csrc/host/usbh.ctest/unit-test/project.ymltest/unit-test/test/device/msc/test_msc_device.ctest/unit-test/test/host/msc/test_msc_host.c
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Comments Outside DiffThese findings sit on lines the diff does not cover, so they could not be posted inline. Each one leaves this list once its file changes.
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tu_edpt_stream_write()andtu_edpt_stream_read()take auint32_tsize but narrowed it touint16_tfor the fifo, so a 65536-byte request became 0 and 65537 became 1. The caller gets 0 back, retries the same size, and the transfer stalls. #2219 fixed this inside CDC; f11adb0 moved CDC onto the shared stream and the clamp was lost.The request is now clamped to
UINT16_MAXat the stream boundary, covering every stream user, and bufferedtud_vendor_n_write()no longer casts before calling it. Clamping to the fifo's free space was avoided because overwritable TX streams (CDC when disconnected, printer) must keep writing.Validation
test_usbd_stream_wide_request: fails on master at 65536, passes with the fix; covers write, read and overwrite mode.pre-commit run --all-filesgreen.stm32f407discoandraspberry_pi_pico. Size: +11 B flash, 0 RAM across all pico examples.raspberry_pi_pico: a temporary cdc_msc build makes onetud_cdc_write/tud_cdc_readcall of the given size and drains the remainder; the host checks count and data.host/cdc_msc_hidalso fail on unrelated branches (run, run).Other 32-to-16-bit wraps found by rescanning the public API:
tuh_msc_read10/write10passedblock_count * block_sizeto the 16-bitusbh_edpt_xfer(). The data stage is now split into 0xFC00-byte transfers, and a short or failed piece ends it. On stm32f723disco, one 192-sector READ(10) timed out on master (2/2) and passes with the fix (4/4), with a valid CSW and data identical to a chunked re-read. HILhost/msc_file_explorerand_freertospass.tuh_edpt_xfer()rejects abuflenaboveUINT16_MAX.tud_mtp_response_send()rejects a container larger thanCFG_TUD_MTP_EP_BUFSIZE.uint16_t, so 66048 bytes for one block read as 512 and walked past the requested LBAs. It now fails with a stall and full residue, following BOT §6.7 cases 4/9. HILdevice/cdc_mscandmsc_dual_lunpass on pico and stm32f723disco.