Description
In 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
Published: 2026-08-15
Score: n/a
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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History

Sat, 15 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-874

Sat, 15 Aug 2026 06:00:00 +0000

Type Values Removed Values Added
Description In 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
Title md/raid5: avoid R5_Overlap races while breaking stripe batches
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-15T05:56:39.802Z

Reserved: 2026-08-09T03:40:39.927Z

Link: CVE-2026-72420

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-15T06:22:15.743

Modified: 2026-08-15T06:22:15.743

Link: CVE-2026-72420

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-15T18:15:03Z

Weaknesses