Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
dm-pcache: validate on-media seg_num against the cache device size
seg_num is read from the crc32c-only superblock, so whoever supplies the cache device on a table load (CAP_SYS_ADMIN) controls it. It sizes cache->segments[] and is the value every later on-media segment id is bounded against, yet it is never checked against the device. Because cache_dev->mapping is the direct map of the pmem, CACHE_DEV_SEGMENT() for a segment id past the device resolves to ordinary kernel memory beyond the mapping; a new-cache init reaching such an id has cache_seg_init() -> cache_dev_zero_range() memset() 12 KiB over that memory – an out-of-bounds write into the kernel heap at table load. A zero seg_num makes the segment allocations ZERO_SIZE_PTR.
Reject a seg_num that is zero, larger than the device can hold, or larger than PCACHE_CACHE_SEGS_MAX before it is used.
Details
- Affected product:
- Debian 10 ELS , Debian 11 ELS
- Affected packages:
- linux @ 4.19.0 (+1 more)