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CVE-2026-90401
md: remove REQ_NOWAIT support from raid1/10/456
Published 2026-09-17 (31 days ago) by the Linux kernel CNA. Subsystem drivers/md. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-90401 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
REQ_NOWAIT support in md personalities that can block internally is fundamentally incomplete. While reads can avoid some blocking paths, write requests can still encounter cases where one mirror succeeds while another returns -EAGAIN. At that point md cannot distinguish queue pressure from a real device failure, so it can neither record a bad block nor safely retry the write without REQ_NOWAIT, leaving mirrors with divergent data. Rather than continue advertising REQ_NOWAIT support for personalities that cannot implement it correctly, remove it from raid1, raid10 and raid456. Keep REQ_NOWAIT for linear and raid0, which only remap bios to their underlying devices; stacked limits will still clear the feature if any component device lacks REQ_NOWAIT support.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/md/md-bitmap.c
drivers/md/md-bitmap.h
drivers/md/md-linear.c
drivers/md/md-llbitmap.c
drivers/md/md.c
drivers/md/raid0.c
drivers/md/raid1-10.c
drivers/md/raid1.c
drivers/md/raid10.c
drivers/md/raid5.c
- What this is
- SOFTWARE RAID (Multiple Disks) SUPPORTMAINTAINERS section matched on drivers/md/md* · linux-raid@vger.kernel.org · Supported
- Kernel module
- md_mod
Check it on the machine
grep -wE 'CONFIG_BLK_DEV_MD|CONFIG_MD|CONFIG_MD_BITMAP' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w md_modPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switches
- CONFIG_BLK_DEV_MD, CONFIG_MD, CONFIG_MD_BITMAP
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-17 (31 days ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/md
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.17 | 6.18.57 | ffcc9ea4e4d1 |
| 5.17 | 7.2.6 | 9bb9504e2d8f |
| 5.17 | 7.3 | 3fe5b7c9fb72 |
| 5.15.111 | 0 | 0 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The REQ_NOWAIT bit that drives the bug is set in blkdev_direct_IO() from IOCB_NOWAIT (pwritev2 RWF_NOWAIT or io_uring io_write() with O_DIRECT) on the md gendisk, then md_submit_bio()->raid1_write_request()/raid10_write_request(). nfsd, ksmbd, nvmet_bdev_execute_rw(), and iSCSI iblock submit ordinary READ/WRITE bios without REQ_NOWAIT, so no protocol message carries the flag.
- AC:LAttack complexity, low
- md_init_stacking_limits() advertised BLK_FEAT_NOWAIT, so member clones kept REQ_NOWAIT and raid1_should_handle_error() ignored their failures. The attacker issues concurrent O_DIRECT nowait writes via io_uring/pwritev2 to fill one member's request queue until it returns BLK_STS_AGAIN while the other mirror completes; no uninfluenced race is required.
- PR:LPrivileges required, low
- blkdev_direct_IO() performs no capable() check. Any process that can open the md node or a stacked dm LV (disk group, container CSI block volume, or a delegated /dev/mdX) can issue RWF_NOWAIT O_DIRECT I/O; init-namespace root is not required.
- UI:NUser interaction, none
- The attacker opens the md block device themselves and issues pwritev2(RWF_NOWAIT) or io_uring io_write(); no separate victim must mount a filesystem, attach media, or confirm an action.
- S:UScope, unchanged
- Divergent raid1/raid10 mirrors and skipped WriteErrorSeen/bad-block recording remain inside the host md array. The bug does not escape a VM, bypass an IOMMU, or cross another security authority.
- C:NConfidentiality impact, none
- raid1_end_write_request() ignore_error only skips WriteErrorSeen and R1BIO_WriteError; it does not read other tenants' data or kernel memory. A failed nowait read forced uptodate in raid1_end_read_request() completes into the attacker's own O_DIRECT buffers.
- I:HIntegrity impact, high
- When one raid1/raid10 clone succeeds and another returns BLK_STS_AGAIN, raid1_should_handle_error() sets ignore_error, raid1_end_write_request() still sets R1BIO_Uptodate, and raid_end_bio_io() reports success while mirrors hold different data and real member failures are not recorded as bad blocks.
- A:HAvailability impact, high
- raid5 make_discard_request() returned without bio_endio() on REQ_NOWAIT, hanging the discard bio. Ignored member failures also leave a disk In_sync after a nowait EAGAIN, so a later loss of the up-to-date mirror makes diverged sectors unrecoverable and can take the array/filesystem offline.