{"id":"CVE-2026-72420","state":"PUBLISHED","title":"md/raid5: avoid R5_Overlap races while breaking stripe batches","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmd/raid5: avoid R5_Overlap races while breaking stripe batches\n\nKCSAN report a race in break_stripe_batch_list() vs. raid5_make_request()\non sh->dev[i].flags (plain word write vs. atomic bit op)..\n\nand .. one possible scenario is:\n\nCPU1                            CPU2\nbreak_stripe_batch_list(sh1)\n-> handle sh2\n-> lock(sh2)\n-> sh2->batch_head = NULL\n-> unlock(sh2)\n-> test_and_clear_bit(R5_Overlap, sh2->dev[i].flags)\n-> wake_up_bit(sh2->dev[i].flags)\n                                raid5_make_request()\n                                -> add_all_stripe_bios(sh2)\n                                -> lock(sh2)\n                                -> stripe_bio_overlaps(sh2) returns true\n\t\t\t\t   batch_head is NULL, so new bio overlap\n\t\t\t\t   exist bio on sh2 -> true\n                                -> set_bit(R5_Overlap, sh2->dev[i].flags)\n                                -> unlock(sh2)\n                                -> wait_on_bit(sh2->dev[i].flags)\n-> sh2->dev[i].flags = sh1->dev[i].flags & ~R5_Overlap\n\nNo wait_up_bit(), CPU2 could be wait_on_bit() forever...\n\nFix by :\n- Expand the protect zone.\n- Use batch_head's device flag's snaphot when no held head_sh->stripe_lock.\n- Move sh/head_sh->batch_head = NULL to the end of protected zone , and ,\n  any concurrent add_all_stripe_bios() grabs sh->stripe_lock now either:\n\t- see batch_head != null, and , is rejected by stripe_bio_overlaps()\n\t  under the lock (no R5_Overlap wait ) , or ,\n\t- sees batch_head == NULL, only after dev[i].flags has already been\n\t  set and the prior R5_Overlap waiters worken.\n\nKCSAN report:\n================================================\n  BUG: KCSAN: data-race in break_stripe_batch_list / raid5_make_request\n\n  write (marked) to 0xffff8e89c8117548 of 8 bytes by task 4042 on cpu 0:\n    raid5_make_request+0xea0/0x2930\n    md_handle_request+0x4a2/0xa40\n    md_submit_bio+0x109/0x1a0\n    __submit_bio+0x2ec/0x390\n    submit_bio_noacct_nocheck+0x457/0x710\n    submit_bio_noacct+0x2a7/0xc20\n    submit_bio+0x56/0x250\n    blkdev_direct_IO+0x54c/0xda0\n    blkdev_write_iter+0x38f/0x570\n    aio_write+0x22b/0x490\n    io_submit_one+0xa51/0xf70\n    __x64_sys_io_submit+0xf7/0x220\n    x64_sys_call+0x1907/0x1c60\n    do_syscall_64+0x130/0x570\n    entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\n  read to 0xffff8e89c8117548 of 8 bytes by task 4010 on cpu 5:\n    break_stripe_batch_list+0x249/0x480\n    handle_stripe_clean_event+0x720/0x9b0\n    handle_stripe+0x32fb/0x4500\n    handle_active_stripes.isra.0+0x6e0/0xa50\n    raid5d+0x7e0/0xba0\n    md_thread+0x15a/0x2d0\n    kthread+0x1e3/0x220\n    ret_from_fork+0x37a/0x410\n    ret_from_fork_asm+0x1a/0x30\n\n  value changed: 0x0000000000000019 -> 0x0000000000000099 --> R5_Overlap","publishedAt":"2026-08-15T05:56:39.802Z","updatedAt":"2026-10-30T12:29:21.031Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"205e33bad8ebf5674fbe6ec3ae3805878abb4f2c","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"158a5480d51969adeb727ff20c6fa96f063e9f9e","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"8031b0d02bd221a5f9add4357e291fc2a527b83a","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"4d919c9b770996365806b6c8d701912d52baa306","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"d684b72dfbd320623ccaab0779aa841190488e7c","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"55b77337bdd088c77461588e5ec094421b89911b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/md/raid5.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.1","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/md/raid5.c"]}],"references":["https://git.kernel.org/stable/c/205e33bad8ebf5674fbe6ec3ae3805878abb4f2c","https://git.kernel.org/stable/c/158a5480d51969adeb727ff20c6fa96f063e9f9e","https://git.kernel.org/stable/c/8031b0d02bd221a5f9add4357e291fc2a527b83a","https://git.kernel.org/stable/c/4d919c9b770996365806b6c8d701912d52baa306","https://git.kernel.org/stable/c/d684b72dfbd320623ccaab0779aa841190488e7c","https://git.kernel.org/stable/c/55b77337bdd088c77461588e5ec094421b89911b"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72420.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72420","state":"PUBLISHED","datePublished":"2026-08-15T05:56:39.802Z","dateUpdated":"2026-10-30T12:29:21.031Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.927Z"},"containers":{"cna":{"title":"md/raid5: avoid R5_Overlap races while breaking stripe batches","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmd/raid5: avoid R5_Overlap races while breaking stripe batches\n\nKCSAN report a race in break_stripe_batch_list() vs. raid5_make_request()\non sh->dev[i].flags (plain word write vs. atomic bit op)..\n\nand .. one possible scenario is:\n\nCPU1                            CPU2\nbreak_stripe_batch_list(sh1)\n-> handle sh2\n-> lock(sh2)\n-> sh2->batch_head = NULL\n-> unlock(sh2)\n-> test_and_clear_bit(R5_Overlap, sh2->dev[i].flags)\n-> wake_up_bit(sh2->dev[i].flags)\n                                raid5_make_request()\n                                -> add_all_stripe_bios(sh2)\n                                -> lock(sh2)\n                                -> stripe_bio_overlaps(sh2) returns true\n\t\t\t\t   batch_head is NULL, so new bio overlap\n\t\t\t\t   exist bio on sh2 -> true\n                                -> set_bit(R5_Overlap, sh2->dev[i].flags)\n                                -> unlock(sh2)\n                                -> wait_on_bit(sh2->dev[i].flags)\n-> sh2->dev[i].flags = sh1->dev[i].flags & ~R5_Overlap\n\nNo wait_up_bit(), CPU2 could be wait_on_bit() forever...\n\nFix by :\n- Expand the protect zone.\n- Use batch_head's device flag's snaphot when no held head_sh->stripe_lock.\n- Move sh/head_sh->batch_head = NULL to the end of protected zone , and ,\n  any concurrent add_all_stripe_bios() grabs sh->stripe_lock now either:\n\t- see batch_head != null, and , is rejected by stripe_bio_overlaps()\n\t  under the lock (no R5_Overlap wait ) , or ,\n\t- sees batch_head == NULL, only after dev[i].flags has already been\n\t  set and the prior R5_Overlap waiters worken.\n\nKCSAN report:\n================================================\n  BUG: KCSAN: data-race in break_stripe_batch_list / raid5_make_request\n\n  write (marked) to 0xffff8e89c8117548 of 8 bytes by task 4042 on cpu 0:\n    raid5_make_request+0xea0/0x2930\n    md_handle_request+0x4a2/0xa40\n    md_submit_bio+0x109/0x1a0\n    __submit_bio+0x2ec/0x390\n    submit_bio_noacct_nocheck+0x457/0x710\n    submit_bio_noacct+0x2a7/0xc20\n    submit_bio+0x56/0x250\n    blkdev_direct_IO+0x54c/0xda0\n    blkdev_write_iter+0x38f/0x570\n    aio_write+0x22b/0x490\n    io_submit_one+0xa51/0xf70\n    __x64_sys_io_submit+0xf7/0x220\n    x64_sys_call+0x1907/0x1c60\n    do_syscall_64+0x130/0x570\n    entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\n  read to 0xffff8e89c8117548 of 8 bytes by task 4010 on cpu 5:\n    break_stripe_batch_list+0x249/0x480\n    handle_stripe_clean_event+0x720/0x9b0\n    handle_stripe+0x32fb/0x4500\n    handle_active_stripes.isra.0+0x6e0/0xa50\n    raid5d+0x7e0/0xba0\n    md_thread+0x15a/0x2d0\n    kthread+0x1e3/0x220\n    ret_from_fork+0x37a/0x410\n    ret_from_fork_asm+0x1a/0x30\n\n  value changed: 0x0000000000000019 -> 0x0000000000000099 --> R5_Overlap"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"205e33bad8ebf5674fbe6ec3ae3805878abb4f2c","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"158a5480d51969adeb727ff20c6fa96f063e9f9e","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"8031b0d02bd221a5f9add4357e291fc2a527b83a","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"4d919c9b770996365806b6c8d701912d52baa306","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"d684b72dfbd320623ccaab0779aa841190488e7c","versionType":"git"},{"version":"fb642b92c267beeefd352af9bc461eac93a7552c","status":"affected","lessThan":"55b77337bdd088c77461588e5ec094421b89911b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/md/raid5.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.1","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/md/raid5.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/205e33bad8ebf5674fbe6ec3ae3805878abb4f2c"},{"url":"https://git.kernel.org/stable/c/158a5480d51969adeb727ff20c6fa96f063e9f9e"},{"url":"https://git.kernel.org/stable/c/8031b0d02bd221a5f9add4357e291fc2a527b83a"},{"url":"https://git.kernel.org/stable/c/4d919c9b770996365806b6c8d701912d52baa306"},{"url":"https://git.kernel.org/stable/c/d684b72dfbd320623ccaab0779aa841190488e7c"},{"url":"https://git.kernel.org/stable/c/55b77337bdd088c77461588e5ec094421b89911b"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - RAID5/md arrays commonly back internet-facing NAS and SAN servers; remote writes via NFS, SMB (ksmbd), or iSCSI/NVMe-oF targets reach raid5_make_request() through the server block layer when flushing data to the array.\nAC:L - The KCSAN race needs concurrent full-stripe writes during batch teardown; an attacker can reliably drive both sides with parallel aio/io_submit or network storage clients hammering the same stripes without depending on uncontrollable timing or rare kernel configs.\nPR:L - Exploitation requires only permission to issue writes that hit the RAID5 device (e.g., a storage client account, local user writing to a filesystem on /dev/md*, or block-device access), not init-namespace root or CAP_SYS_ADMIN on the host.\nUI:N - Triggering the race is fully automated through concurrent I/O requests; no victim click, mount, or other interactive action beyond the attacker's own write traffic is required.\nS:U - Impact is confined to kernel RAID5 I/O handling and data on the affected host or its directly attached arrays; it does not cross VM, container, or IOMMU security boundaries.\nC:H - KCSAN documents a data race on r5dev->flags where break_stripe_batch_list() plain-writes the whole flags word concurrent with atomic bitops, which can corrupt R5_UPTODATE/R5_Insync state and expose stale stripe cache contents to readers.\nI:H - The same non-atomic flags overwrite can desynchronize stripe bookkeeping and in-flight write state during batch break, enabling incorrect parity/rebuild decisions and corrupted or misdirected full-stripe writes to RAID member devices.\nA:H - The documented failure leaves raid5_make_request() threads stuck in TASK_UNINTERRUPTIBLE wait_on_bit() forever when R5_Overlap is cleared without wake_up_bit(), hanging I/O workers and enabling repeatable denial of storage service."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:29:21.031Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.1","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.1","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.1","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.1","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.1","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.1","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-72420","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T18:49:28.867554Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T18:55:22.947Z"}}]}}}