{"id":"CVE-2025-38066","title":"dm cache: prevent BUG_ON by blocking retries on failed device resumes","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ndm cache: prevent BUG_ON by blocking retries on failed device resumes\n\nA cache device failing to resume due to mapping errors should not be\nretried, as the failure leav…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 66a636356647a9be8885c2ce2948de126577698a < c614584c2a66b538f469089ac089457a34590c14","Linux >= 66a636356647a9be8885c2ce2948de126577698a < c5356a5e80442131e2714d0d26bb110590e4e568","Linux >= 66a636356647a9be8885c2ce2948de126577698a < 025c8f477625eb39006ded650e7d027bcfb20e79","Linux >= 66a636356647a9be8885c2ce2948de126577698a < 00586b78eeb7c626a14ca13453a1631f88a7cf36","Linux >= 66a636356647a9be8885c2ce2948de126577698a < 3986ef4a9b6a0d9c28bc325d8713beba5e67586f","Linux >= 66a636356647a9be8885c2ce2948de126577698a < cc80a5cc520939d0a7d071cc4ae4b3c55ef171d0","Linux >= 66a636356647a9be8885c2ce2948de126577698a < f3128e3074e8af565cc6a66fe3384a56df87f803","Linux >= 66a636356647a9be8885c2ce2948de126577698a < 5da692e2262b8f81993baa9592f57d12c2703dea","Linux 4.2"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-05T20:48:55.834588Z"},"published":"2025-06-18","updated":"2026-11-05","sourceUpdated":"2026-11-05T20:52:14.383Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-38066","references":[{"url":"https://git.kernel.org/stable/c/c614584c2a66b538f469089ac089457a34590c14"},{"url":"https://git.kernel.org/stable/c/c5356a5e80442131e2714d0d26bb110590e4e568"},{"url":"https://git.kernel.org/stable/c/025c8f477625eb39006ded650e7d027bcfb20e79"},{"url":"https://git.kernel.org/stable/c/00586b78eeb7c626a14ca13453a1631f88a7cf36"},{"url":"https://git.kernel.org/stable/c/3986ef4a9b6a0d9c28bc325d8713beba5e67586f"},{"url":"https://git.kernel.org/stable/c/cc80a5cc520939d0a7d071cc4ae4b3c55ef171d0"},{"url":"https://git.kernel.org/stable/c/f3128e3074e8af565cc6a66fe3384a56df87f803"},{"url":"https://git.kernel.org/stable/c/5da692e2262b8f81993baa9592f57d12c2703dea"}],"tags":["cve.org"],"epss":0.00205,"epssPercentile":0.10514,"ingestedAt":"2026-11-05T22:38:31.914Z","slug":"CVE-2025-38066","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ndm cache: prevent BUG_ON by blocking retries on failed device resumes\n\nA cache device failing to resume due to mapping errors should not be\nretried, as the failure leaves a partially initialized policy object.\nRepeating the resume operation risks triggering BUG_ON when reloading\ncache mappings into the incomplete policy object.\n\nReproduce steps:\n\n1. create a cache metadata consisting of 512 or more cache blocks,\n   with some mappings stored in the first array block of the mapping\n   array. Here we use cache_restore v1.0 to build the metadata.\n\ncat <<EOF >> cmeta.xml\n<superblock uuid=\"\" block_size=\"128\" nr_cache_blocks=\"512\" \\\npolicy=\"smq\" hint_width=\"4\">\n  <mappings>\n    <mapping cache_block=\"0\" origin_block=\"0\" dirty=\"false\"/>\n  </mappings>\n</superblock>\nEOF\ndmsetup create cmeta --table \"0 8192 linear /dev/sdc 0\"\ncache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2\ndmsetup remove cmeta\n\n2. wipe the second array block of the mapping array to simulate\n   data degradations.\n\nmapping_root=$(dd if=/dev/sdc bs=1c count=8 skip=192 \\\n2>/dev/null | hexdump -e '1/8 \"%u\\n\"')\nablock=$(dd if=/dev/sdc bs=1c count=8 skip=$((4096*mapping_root+2056)) \\\n2>/dev/null | hexdump -e '1/8 \"%u\\n\"')\ndd if=/dev/zero of=/dev/sdc bs=4k count=1 seek=$ablock\n\n3. try bringing up the cache device. The resume is expected to fail\n   due to the broken array block.\n\ndmsetup create cmeta --table \"0 8192 linear /dev/sdc 0\"\ndmsetup create cdata --table \"0 65536 linear /dev/sdc 8192\"\ndmsetup create corig --table \"0 524288 linear /dev/sdc 262144\"\ndmsetup create cache --notable\ndmsetup load cache --table \"0 524288 cache /dev/mapper/cmeta \\\n/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0\"\ndmsetup resume cache\n\n4. try resuming the cache again. An unexpected BUG_ON is triggered\n   while loading cache mappings.\n\ndmsetup resume cache\n\nKernel logs:\n\n(snip)\n------------[ cut here ]------------\nkernel BUG at drivers/md/dm-cache-policy-smq.c:752!\nOops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI\nCPU: 0 UID: 0 PID: 332 Comm: dmsetup Not tainted 6.13.4 #3\nRIP: 0010:smq_load_mapping+0x3e5/0x570\n\nFix by disallowing resume operations for devices that failed the\ninitial attempt.\n\n## Affected\n\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < c614584c2a66b538f469089ac089457a34590c14`\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < c5356a5e80442131e2714d0d26bb110590e4e568`\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < 025c8f477625eb39006ded650e7d027bcfb20e79`\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < 00586b78eeb7c626a14ca13453a1631f88a7cf36`\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < 3986ef4a9b6a0d9c28bc325d8713beba5e67586f`\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < cc80a5cc520939d0a7d071cc4ae4b3c55ef171d0`\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < f3128e3074e8af565cc6a66fe3384a56df87f803`\n- `Linux >= 66a636356647a9be8885c2ce2948de126577698a < 5da692e2262b8f81993baa9592f57d12c2703dea`\n- `Linux 4.2`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}