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CVE-2026-97520
gfs2: move quota_init qc iterator increment
Published 2026-09-24 (24 days ago) by the Linux kernel CNA. Subsystem fs/gfs2. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-97520 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| 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. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Move qc++ from the loop body into the for-loop increment expression in gfs2_quota_init(). This keeps iterator progression explicit and avoids mixing pointer advance with duplicate-slot handling in the loop body.
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.
fs/gfs2/quota.c
- What this is
- GFS2 FILE SYSTEMMAINTAINERS section matched on fs/gfs2/ · gfs2@lists.linux.dev · Supported
- Kernel module
- gfs2
Check it on the machine
grep -w CONFIG_GFS2_FS /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 gfs2Prints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_GFS2_FS
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
- 2026-09-24 (24 days ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 1.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/gfs2
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.11 | 6.12.111 | 04ec2f3b29b3 |
| 6.11 | 6.18.53 | 21a50a9373ad |
| 6.11 | 7.2 | 942202677f8f |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
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 malformed bytes are on-disk struct gfs2_quota_change records in the per-node quota_change file. gfs2_quota_init() reads them via gfs2_meta_ra() from gfs2_get_tree()→get_tree_bdev()→gfs2_fill_super()→gfs2_make_fs_rw(); no NFS/SMB/TCP message carries qc_id or qc_change.
- AC:LAttack complexity, low
- A crafted quota_change file with two non-zero qc_change entries sharing qc_id, the duplicate in the last slot of a QC block, makes the pre-fix body qc++ then memset(qc,0,sizeof(*qc)) run on every read-write mount of that image, with no race.
- PR:NPrivileges required, none
- Crafting the image needs no host account. gfs2_fs_type.fs_flags is only FS_REQUIRES_DEV (no FS_USERNS_MOUNT), so mount_capable() is capable(CAP_SYS_ADMIN) in init_user_ns; that privileged mount of the attacker image is scored as UI:R, not attacker privilege.
- UI:RUser interaction, required
- gfs2_quota_init() runs only from gfs2_make_fs_rw() after gfs2_fill_super() or gfs2_reconfigure() attaches the attacker-supplied block device. Because gfs2 is not FS_USERNS_MOUNT, a victim or administrator must mount that image read-write before the duplicate-slot memset runs.
- S:UScope, unchanged
- The out-of-bounds memset in gfs2_quota_init() corrupts page-cache memory in the host kernel that mounted the volume; this is not a KVM/Xen guest-to-host escape or an IOMMU/DMA bypass.
- C:NConfidentiality impact, none
- The duplicate path only stores 16 zeros through the already-advanced qc pointer; it does not load adjacent kernel bytes or copy them to userspace.
- I:HIntegrity impact, high
- Pre-fix, qc++ runs before memset(qc,0,sizeof(*qc)). sd_qc_per_block is (sb_bsize-24)/16, leaving 8 bytes of padding, so a last-slot duplicate stores 8 zeros past bh->b_data+sb_bsize of the gfs2_getbuf() buffer_head: a kernel out-of-bounds write.
- A:HAvailability impact, high
- Those 8 zeros past the QC buffer_head land in the next folio/page (or the next BH in the same folio when sb_bsize<PAGE_SIZE) and can oops the kernel when that memory is live, poisoned, or KASAN-guarded.