The Nuvoton NPCX eSPI driver parses Target-Attached-Flash (TAF) requests in espi_taf_parse() (drivers\/espi\/espi_npcx.c), taking the 12-bit length field directly out of the request header in the FLASHRXBUF FIFO. For write and RPMC OP1 requests it copied DIV_ROUND_UP(len, 4) words into struct espi_taf_pckt.src, a fixed 16-word (64-byte) member of a static structure, without ever comparing the length against that buffer or against the negotiated eSPI receive payload size (rx-plsize, 64 bytes on all in-tree NPCX\/NPCK SoCs). Both the loop counter and the word count were uint8_t, so the copy ran up to 255 iterations.<\/p>\n
An eSPI controller that emits a flash request whose header claims a payload larger than the negotiated maximum therefore drives up to 239 32-bit stores past the end of the structure \u2014 roughly 956 bytes of out-of-bounds write into .bss \u2014 from the eSPI flash receive interrupt handler, while the source reads walk past the end of the 18-word FLASHRXBUF register array into neighbouring eSPI registers. The same unvalidated length was then passed on to flash_write() in espi_taf_npcx_flash_write() with the 64-byte src buffer as source, reading up to 4 KB of adjacent controller SRAM into SPI flash at a host-chosen address, where the host can read it back. A related fixed-size stack buffer in taf_npcx_completion_handler() was overflowed by four bytes on the maximum-size completion path on SoCs whose tx-plsize is 64.<\/p>\n
The defect is reachable only from the eSPI host side, and only by a request that violates the negotiated payload size, so it requires host firmware or bus-level control rather than ordinary host software; a compliant maximum-length write fits the buffer exactly and is handled correctly. Because TAF exists specifically so that the embedded controller arbitrates host access to shared flash (espi_taf_check_read_protect() \/ espi_taf_check_write_protect()), corrupting controller memory from a host-supplied field crosses the trust boundary the feature asserts; consequences range from controller crash or hang to corruption of driver state that gates the flash protection regions.<\/p>\n
The fix widens the counters, rejects any request whose word count exceeds both ARRAY_SIZE(FLASHRXBUF) – NPCX_ESPI_FLASH_HEADER_ADDRESS_LEN and NPCX_TAF_RX_PAYLOAD_WORDS (derived from the devicetree rx-plsize), marks such packets with a new invalid_flag so espi_taf_work() answers them with an unsuccessful completion instead of processing them, bounds the transmit payload against FLASHTXBUF, and adds a default case for unsupported cycle types. Only configurations with CONFIG_ESPI_TAF enabled on an NPCX\/NPCK target are affected; no in-tree board enables it by default.<\/p>\n","protected":false},"excerpt":{"rendered":"
The Nuvoton NPCX eSPI driver parses Target-Attached-Flash (TAF) requests in espi_taf_parse() (drivers\/espi\/espi_npcx.c), taking the 12-bit length field directly out of the request header in the FLASHR<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-44281","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/44281","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=44281"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=44281"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=44281"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}