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CVE-2026-98361
RDMA/rxe: Restore HMM_PFN_WRITE check in ODP write paths
Published 2026-10-06 (13 days ago) by the Linux kernel CNA. Subsystem drivers/infiniband. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-98361 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.2.8-1 | Update the kernel and reboot. Fixed in 7.2.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.8-1 | Update the kernel and reboot. Fixed in 7.2.8-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Commit 0b261d7c1cd3 ("RDMA/rxe: Break endless pagefault loop for RO pages") dropped the access permission test from rxe_check_pagefault() and left only HMM_PFN_VALID. A page faulted in read-only, for example a page-cache folio behind a PROT_READ file mapping, then satisfies the check and ODP write operations (RDMA WRITE, RDMA READ response, SEND payload, atomics) modify it through kmap without ever breaking CoW. An unprivileged user can register an ODP MR over such a mapping and have incoming RDMA traffic overwrite the page cache of a file it only holds O_RDONLY, including /etc/passwd or setuid binaries. This is the same primitive class as Dirty COW and CVE-2022-2590. mlx5 has the missing invariant: its ODP path sets the device write bit only for pfns that carry HMM_PFN_WRITE. Restore it in rxe by requiring HMM_PFN_WRITE in rxe_check_pagefault() for every operation except RXE_PAGEFAULT_RDONLY. A write to a non-writable VMA now fails the one fault attempt with -EPERM from hmm_vma_fault() instead of re-faulting forever. For a writable VMA the fault breaks CoW and the write lands in the private page. Keep pmem flushes on the read-only check. arch_wb_cache_pmem() never modifies memory, and the FLUSH access bits do not make the umem writable, so classifying flushes as writes would make every flush against a flush-only MR fail.
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/infiniband/sw/rxe/rxe_odp.c
- What this is
- SOFT-ROCE DRIVER (rxe)MAINTAINERS section matched on drivers/infiniband/sw/rxe/ · linux-rdma@vger.kernel.org · Supported
- Kernel module
- rdma_rxe
Check it on the machine
grep -wE 'CONFIG_INFINIBAND|CONFIG_INFINIBAND_ON_DEMAND_PAGING|CONFIG_RDMA_RXE' /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 rdma_rxePrints 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. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae
- ?
- not established - no Makefile entry for the affected file
- M
- a module where it is built at all; some flavours do not build it
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_INFINIBAND, CONFIG_INFINIBAND_ON_DEMAND_PAGING, CONFIG_RDMA_RXE
- 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
- 2026-10-06 (13 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/infiniband
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.16 | 6.18.54 | c6f56982ec5c |
| 6.16 | 7.2.8 | 2d6c6f94d3e1 |
| 6.16 | 7.3 | 769001ce838d |
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 bug needs an ODP MR with remote write access, created by a local user through uverbs reg_user_mr (rxe_reg_user_mr -> rxe_odp_mr_init_user) over their own PROT_READ file mapping. The RDMA WRITE/SEND/atomic that reaches rxe_odp_map_range_and_lock can come from the same user's QP on the same rxe device, and a remote peer cannot set up this state on its own.
- AC:LAttack complexity, low
- Once an rxe device exists, the attacker controls every step: mmap a readable file PROT_READ, fault the pages in read-only, register the MR so the snapshot rxe_odp_init_pages() records them HMM_PFN_VALID without WRITE, then post an RDMA WRITE to it. rxe_check_pagefault() only tested VALID, so the result is deterministic with no race.
- PR:LPrivileges required, low
- Registering an MR and QPs on /dev/infiniband/uverbs* needs no capability, and the device is normally world-accessible. Only creating the rxe link (rdma link add, RDMA_NL_ADMIN_PERM) needs CAP_NET_ADMIN in init_user_ns. The attacker needs only read access to the target file.
- UI:NUser interaction, none
- The attacker does everything with their own syscalls and RDMA operations on mappings they own; no other user or admin has to act at the time of the attack.
- S:UScope, unchanged
- The impact is writes to the page cache through kmap_local_page in __rxe_odp_mr_copy, inside the same kernel authority. It is a standard local privilege escalation and crosses no VM or IOMMU boundary.
- C:HConfidentiality impact, high
- Overwriting the cached contents of root-owned files the user can only read (/etc/passwd, /etc/shadow handling, setuid binaries) leads to root, which exposes all data on the system, as with Dirty COW and CVE-2022-2590.
- I:HIntegrity impact, high
- __rxe_odp_mr_copy (RXE_TO_MR_OBJ) and rxe_odp_do_atomic_op/atomic_write write attacker-chosen bytes into read-only page-cache folios without breaking CoW, so arbitrary file contents can be modified and setuid binaries rewritten for code execution as root.
- A:HAvailability impact, high
- With write access to the page cache of system binaries and libraries, the attacker can corrupt critical files such as init and libc, or take root, and make the system unusable.