{"id":"CVE-2026-23238","summary":"romfs: check sb_set_blocksize() return value","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nromfs: check sb_set_blocksize() return value\n\nromfs_fill_super() ignores the return value of sb_set_blocksize(), which\ncan fail if the requested block size is incompatible with the block\ndevice's configuration.\n\nThis can be triggered by setting a loop device's block size larger than\nPAGE_SIZE using ioctl(LOOP_SET_BLOCK_SIZE, 32768), then mounting a romfs\nfilesystem on that device.\n\nWhen sb_set_blocksize(sb, ROMBSIZE) is called with ROMBSIZE=4096 but the\ndevice has logical_block_size=32768, bdev_validate_blocksize() fails\nbecause the requested size is smaller than the device's logical block\nsize. sb_set_blocksize() returns 0 (failure), but romfs ignores this and\ncontinues mounting.\n\nThe superblock's block size remains at the device's logical block size\n(32768). Later, when sb_bread() attempts I/O with this oversized block\nsize, it triggers a kernel BUG in folio_set_bh():\n\n    kernel BUG at fs/buffer.c:1582!\n    BUG_ON(size \u003e PAGE_SIZE);\n\nFix by checking the return value of sb_set_blocksize() and failing the\nmount with -EINVAL if it returns 0.","modified":"2026-04-02T13:12:16.980633Z","published":"2026-03-04T14:38:42.477Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23238.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2c5829cd8fbbc91568c520b666898f57cdcb8cf6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4b71ad7676564a94ec5f7d18298f51e8ae53db73"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9b203b8ddd7359270e8a694d0584743555128e2c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a381f0f61b35c8894b0bd0d6acef2d8f9b08b244"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ab7ad7abb3660c58ffffdf07ff3bb976e7e0afa0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cbd9931e6456822067725354d83446c5bb813030"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f2521ab1f63a8c244f06a080319e5ff9a2e1bd95"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23238.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23238"},{"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":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2"},{"fixed":"a381f0f61b35c8894b0bd0d6acef2d8f9b08b244"},{"fixed":"f2521ab1f63a8c244f06a080319e5ff9a2e1bd95"},{"fixed":"2c5829cd8fbbc91568c520b666898f57cdcb8cf6"},{"fixed":"cbd9931e6456822067725354d83446c5bb813030"},{"fixed":"9b203b8ddd7359270e8a694d0584743555128e2c"},{"fixed":"4b71ad7676564a94ec5f7d18298f51e8ae53db73"},{"fixed":"ab7ad7abb3660c58ffffdf07ff3bb976e7e0afa0"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23238.json"}}],"schema_version":"1.7.5"}