dm-pcache: validate kset key_num and intra-segment bounds

Summary

In the Linux kernel, the following vulnerability has been resolved: dm-pcache: validate kset key_num and intra-segment bounds Two more fields decoded from the cache device go unbounded. The kset key_num drives cache_kset_crc() and the replay loop in cache_replay(), the writeback worker and the GC worker, but only the magic and a fixed-seed CRC are checked first, so a non-last kset whose key_num exceeds the PCACHE_KSET_KEYS_MAX buffer reads past its end before the CRC compare. A key's intra-segment offset and length in cache_key_decode() are taken verbatim, so a key running past its segment is replayed into the cache tree and the data CRC check and every later read hit then copy adjacent persistent memory into the caller's bio -- an out-of-bounds read that leaks to user space. Both fields are controlled by whoever supplies the cache device (CAP_SYS_ADMIN); the CRC seed is public. Add kset_onmedia_valid() to bound key_num before any kset read, and reject a key whose offset plus length, computed in 64 bits, exceeds the segment data_size. Valid metadata is unaffected.

Timeline

1. Sep 11, 2026, 7:42 PM UTCCVE published
2. Oct 19, 2026, 8:45 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 · fixed in d8caf96040a06096276ab72f5e1e8547c014c564; From 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 · fixed in 5ac38f4b4862fad6e7270fde5c3356a822ce74ca; From 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 · fixed in f11deb032fd84081e7831cffcba895d893054a22

• Linux Linux

  6.18

• KernelLinux

  From 6.18.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 3