CVE-2025-21861: mm/migrate_device: don't add folio to be freed to LRU in migrate_device_finalize()
Description
In the Linux kernel, the following vulnerability has been resolved:
mm/migrate_device: don't add folio to be freed to LRU in migrate_device_finalize()
If migration succeeded, we called
folio_migrate_flags()->mem_cgroup_migrate() to migrate the memcg from the
old to the new folio. This will set memcg_data of the old folio to 0.
Similarly, if migration failed, memcg_data of the dst folio is left unset.
If we call folio_putback_lru() on such folios (memcg_data == 0), we will
add the folio to be freed to the LRU, making memcg code unhappy. Running
the hmm selftests:
# ./hmm-tests
...
# RUN hmm.hmm_device_private.migrate ...
[ 102.078007][T14893] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x7ff27d200 pfn:0x13cc00
[ 102.079974][T14893] anon flags: 0x17ff00000020018(uptodate|dirty|swapbacked|node=0|zone=2|lastcpupid=0x7ff)
[ 102.082037][T14893] raw: 017ff00000020018 dead000000000100 dead000000000122 ffff8881353896c9
[ 102.083687][T14893] raw: 00000007ff27d200 0000000000000000 00000001ffffffff 0000000000000000
[ 102.085331][T14893] page dumped because: VM_WARN_ON_ONCE_FOLIO(!memcg && !mem_cgroup_disabled())
[ 102.087230][T14893] ------------[ cut here ]------------
[ 102.088279][T14893] WARNING: CPU: 0 PID: 14893 at ./include/linux/memcontrol.h:726 folio_lruvec_lock_irqsave+0x10e/0x170
[ 102.090478][T14893] Modules linked in:
[ 102.091244][T14893] CPU: 0 UID: 0 PID: 14893 Comm: hmm-tests Not tainted 6.13.0-09623-g6...
Classification
CVE ID: CVE-2025-21861
Affected Products
Vendor: Linux, Linux
Product: Linux, Linux
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.02% (probability of being exploited)
EPSS Percentile: 1.72% (scored less or equal to compared to others)
EPSS Date: 2025-04-10 (when was this score calculated)
References
https://nvd.nist.gov/vuln/detail/CVE-2025-21861https://git.kernel.org/stable/c/3f9240d59e9a95d19f06120bfd1d0e681c6c0ac7
https://git.kernel.org/stable/c/069dd21ea8262204f94737878389c2815a054a9e
https://git.kernel.org/stable/c/41cddf83d8b00f29fd105e7a0777366edc69a5cf