GHSA-3F2P-V853-3W76
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In the Linux kernel, the following vulnerability has been resolved:
md/raid5: avoid R5_Overlap races while breaking stripe batches
KCSAN report a race in break_stripe_batch_list() vs. raid5_make_request() on sh->dev[i].flags (plain word write vs. atomic bit op)..
and .. one possible scenario is:
CPU1 CPU2 break_stripe_batch_list(sh1) -> handle sh2 -> lock(sh2) -> sh2->batch_head = NULL -> unlock(sh2) -> test_and_clear_bit(R5_Overlap, sh2->dev[i].flags) -> wake_up_bit(sh2->dev[i].flags) raid5_make_request() -> add_all_stripe_bios(sh2) -> lock(sh2) -> stripe_bio_overlaps(sh2) returns true batch_head is NULL, so new bio overlap exist bio on sh2 -> true -> set_bit(R5_Overlap, sh2->dev[i].flags) -> unlock(sh2) -> wait_on_bit(sh2->dev[i].flags) -> sh2->dev[i].flags = sh1->dev[i].flags & ~R5_Overlap
No wait_up_bit(), CPU2 could be wait_on_bit() forever...
Fix by : - Expand the protect zone. - Use batch_head's device flag's snaphot when no held head_sh->stripe_lock. - Move sh/head_sh->batch_head = NULL to the end of protected zone , and , any concurrent add_all_stripe_bios() grabs sh->stripe_lock now either: - see batch_head != null, and , is rejected by stripe_bio_overlaps() under the lock (no R5_Overlap wait ) , or , - sees batch_head == NULL, only after dev[i].flags has already been set and the prior R5_Overlap waiters worken.
KCSAN report:
BUG: KCSAN: data-race in break_stripe_batch_list / raid5_make_request
write (marked) to 0xffff8e89c8117548 of 8 bytes by task 4042 on cpu 0: raid5_make_request+0xea0/0x2930 md_handle_request+0x4a2/0xa40 md_submit_bio+0x109/0x1a0 __submit_bio+0x2ec/0x390 submit_bio_noacct_nocheck+0x457/0x710 submit_bio_noacct+0x2a7/0xc20 submit_bio+0x56/0x250 blkdev_direct_IO+0x54c/0xda0 blkdev_write_iter+0x38f/0x570 aio_write+0x22b/0x490 io_submit_one+0xa51/0xf70 __x64_sys_io_submit+0xf7/0x220 x64_sys_call+0x1907/0x1c60 do_syscall_64+0x130/0x570 entry_SYSCALL_64_after_hwframe+0x76/0x7e
read to 0xffff8e89c8117548 of 8 bytes by task 4010 on cpu 5: break_stripe_batch_list+0x249/0x480 handle_stripe_clean_event+0x720/0x9b0 handle_stripe+0x32fb/0x4500 handle_active_stripes.isra.0+0x6e0/0xa50 raid5d+0x7e0/0xba0 md_thread+0x15a/0x2d0 kthread+0x1e3/0x220 ret_from_fork+0x37a/0x410 ret_from_fork_asm+0x1a/0x30
value changed: 0x0000000000000019 -> 0x0000000000000099 --> R5_Overlap
{
"affected": [],
"aliases": [
"CVE-2026-72420"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:15Z",
"severity": "HIGH"
},
"details": "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-\u003edev[i].flags (plain word write vs. atomic bit op)..\n\nand .. one possible scenario is:\n\nCPU1 CPU2\nbreak_stripe_batch_list(sh1)\n-\u003e handle sh2\n-\u003e lock(sh2)\n-\u003e sh2-\u003ebatch_head = NULL\n-\u003e unlock(sh2)\n-\u003e test_and_clear_bit(R5_Overlap, sh2-\u003edev[i].flags)\n-\u003e wake_up_bit(sh2-\u003edev[i].flags)\n raid5_make_request()\n -\u003e add_all_stripe_bios(sh2)\n -\u003e lock(sh2)\n -\u003e 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 -\u003e true\n -\u003e set_bit(R5_Overlap, sh2-\u003edev[i].flags)\n -\u003e unlock(sh2)\n -\u003e wait_on_bit(sh2-\u003edev[i].flags)\n-\u003e sh2-\u003edev[i].flags = sh1-\u003edev[i].flags \u0026 ~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\u0027s device flag\u0027s snaphot when no held head_sh-\u003estripe_lock.\n- Move sh/head_sh-\u003ebatch_head = NULL to the end of protected zone , and ,\n any concurrent add_all_stripe_bios() grabs sh-\u003estripe_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 -\u003e 0x0000000000000099 --\u003e R5_Overlap",
"id": "GHSA-3f2p-v853-3w76",
"modified": "2026-08-17T06:33:29Z",
"published": "2026-08-15T06:32:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72420"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4d919c9b770996365806b6c8d701912d52baa306"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/55b77337bdd088c77461588e5ec094421b89911b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8031b0d02bd221a5f9add4357e291fc2a527b83a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d684b72dfbd320623ccaab0779aa841190488e7c"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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