{"id":"CVE-2026-93048","summary":"mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()\n\nmtd_add_partition() does not reject the special offset value\nMTDPART_OFS_RETAIN (-3), which leads to a WARN_ON in\nadd_mtd_device() when called through the BLKPG ioctl on NAND\ndevices. The RETAIN value depends on cur_offset being the end of\nthe previous partition, but in the dynamic partition path\ncur_offset equals the offset argument itself, causing undefined\nbehavior.\n\nCommit 5daa7b21496a (\"mtd: prepare partition add and del functions\nfor ioctl requests\") introduced mtd_add_partition() and correctly\nrejected MTDPART_OFS_APPEND (-1) and MTDPART_OFS_NXTBLK (-2),\nsince those special offsets rely on cur_offset tracking the\nprevious partition's end. However, commit 1a31368bf92e (\"mtd: add a flags\nfor partitions which should just leave smth. after them\")\nlater added MTDPART_OFS_RETAIN (-3) for the static\npartition table path without updating mtd_add_partition() to\nalso reject this value.\n\nWith offset=-3 passed via BLKPG, the RETAIN size calculation in\nallocate_partition() underflows (parent_size - 0xFFFFFFFFFFFFFFFD\n= parent_size + 3). If the underflow result does not appear to\nleave enough space, allocate_partition() jumps to out_register via\ngoto, skipping erasesize initialization. This results in\nerasesize=0, which triggers:\n\nWARN_ON((!mtd-\u003eerasesize || !master-\u003e_erase) &&\n\t\t!(mtd-\u003eflags & MTD_NO_ERASE))\n\nin add_mtd_device(). If the underflow result appears to leave\nenough space, a bogus partition size is calculated, but the\n\"out of reach\" sanity check catches the invalid offset and\ncreates a disabled empty partition (offset=0, size=0) instead\nof returning an error.\n\nFix this by adding MTDPART_OFS_RETAIN to the rejection list in\nmtd_add_partition(), consistent with the existing handling of\nAPPEND and NXTBLK.","modified":"2026-09-19T03:47:26.854731173Z","published":"2026-09-17T16:10:39.008Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93048.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/181c1bff940e7d3e34ca485d37e3cdbfe409203c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/398aca2f90122d5abbabff1079deaeb885fe9e40"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6aaab2ace3f7b55733d904e5549acf8405f03642"},{"type":"WEB","url":"https://git.kernel.org/stable/c/701c3ae7273e1adc20db5d97c42e0139b479f16b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a536eb57be58442b19398b2783071007ecfb1735"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b759d5bb6265419344ee9729fd0dc07ad85719d8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c645f6dd1af2ecc70fd3578e141f2f71fa9e4eff"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e204e5c49a012f99638633fdbd773e3c86260053"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93048.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93048"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"1a31368bf92ef2a7da3ba379672c405bd2751df9"},{"fixed":"701c3ae7273e1adc20db5d97c42e0139b479f16b"},{"fixed":"6aaab2ace3f7b55733d904e5549acf8405f03642"},{"fixed":"181c1bff940e7d3e34ca485d37e3cdbfe409203c"},{"fixed":"a536eb57be58442b19398b2783071007ecfb1735"},{"fixed":"e204e5c49a012f99638633fdbd773e3c86260053"},{"fixed":"398aca2f90122d5abbabff1079deaeb885fe9e40"},{"fixed":"c645f6dd1af2ecc70fd3578e141f2f71fa9e4eff"},{"fixed":"b759d5bb6265419344ee9729fd0dc07ad85719d8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93048.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.2.0"},{"fixed":"5.10.270"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.221"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.188"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.157"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93048.json"}}],"schema_version":"1.9.0"}