CVE-2026-23238
Description
In the Linux kernel, the following vulnerability has been resolved: romfs: check sb_set_blocksize() return value romfs_fill_super() ignores the return value of sb_set_blocksize(), which can fail if the requested block size is incompatible with the block device's configuration. This can be triggered by setting a loop device's block size larger than PAGE_SIZE using ioctl(LOOP_SET_BLOCK_SIZE, 32768), then mounting a romfs filesystem on that device. When sb_set_blocksize(sb, ROMBSIZE) is called with ROMBSIZE=4096 but the device has logical_block_size=32768, bdev_validate_blocksize() fails because the requested size is smaller than the device's logical block size. sb_set_blocksize() returns 0 (failure), but romfs ignores this and continues mounting. The superblock's block size remains at the device's logical block size (32768). Later, when sb_bread() attempts I/O with this oversized block size, it triggers a kernel BUG in folio_set_bh(): kernel BUG at fs/buffer.c:1582! BUG_ON(size > PAGE_SIZE); Fix by checking the return value of sb_set_blocksize() and failing the mount with -EINVAL if it returns 0.
How to fix
- linux linux_kernel5.10.251, 5.15.201, 6.1.164, 6.6.127, 6.12.74, 6.18.13 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| linux linux_kernel | 2.6.12.1 ≤ v < 5.10.251, 5.11 ≤ v < 5.15.201, 5.16 ≤ v < 6.1.164, 6.2 ≤ v < 6.6.127, 6.7 ≤ v < 6.12.74, 6.13 ≤ v < 6.18.13, 2.6.12, 6.19 | 5.10.251, 5.15.201, 6.1.164, 6.6.127, 6.12.74, 6.18.13 |
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