CVE-2026-89483: nvme: zero the discard fallback page

CVE-2026-89483: nvme: zero the discard fallback page

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

nvme: zero the discard fallback page

nvme_setup_discard() always maps sizeof(struct nvme_dsm_range) *
NVME_DSM_MAX_RANGES = 4096 bytes as the DSM payload however many ranges
the command declares, because some devices ignore the 'Number of Ranges'
field - the Fixes: commit records two that read past the declared ranges.
A single-range discard fills only the first 16 bytes.

Normally the buffer comes from kzalloc() and the other 4080 bytes are
zero.  When that allocation fails the code falls back to the
per-controller ctrl->discard_page, which nvme_init_ctrl() obtains with
alloc_page(GFP_KERNEL) and nothing ever zeroes, so those 4080 bytes are
whatever the page last held and are handed to the controller.  Reaching
it requires the kzalloc(GFP_ATOMIC | __GFP_NOWARN) to fail, that is
memory pressure; it is not remotely triggerable.  Failing the allocation
under KMSAN reproduces it, with the leaked tail full of vmemmap struct
page pointers.  The extent in the report is a partial transfer of the
payload, not the whole 4096 bytes; the 16-byte boundary in it is the one
declared range:

[   11.991601] BUG: KMSAN: uninit-value in dma_map_phys+0x14c8/0x1900
[   11.991969]  dma_map_phys+0x14c8/0x1900
[   11.992220]  dma_map_page_attrs+0xcf/0x130
[   11.992485]  e1000_xmit_frame+0x4099/0x6d10
[   11.992768]  dev_hard_start_xmit+0x22f/0xa80
[   11.993068]  sch_direct_xmit+0x35c/0xcb0
[   11.993315]  __dev_queue_xmit+0x1ee5/0x5eb0
[   11.993608]  ip_finish_output2+0x1903/0x1c30
[   11.993881]  ip_finish_output+0x288/0x870
[   11.994125]  ip_output+0x15e/0x400
[   11.994365]  __ip_queue_xmit+0x1e85/0x1fb0
[   11.994639]  ip_queue_xmit+0x60/0x80
[   11.994899]  __tcp_transmit_skb+0x4e71/0x5fa0
[   11.995210]  tcp_write_xmit+0x3a36/0x9160
[   11.995533]  __tcp_push_pending_frames+0xc5/0x3c0
[   11.995854]  tcp_push+0x7dc/0x840
[   11.996076]  tcp_sendmsg_locked+0x766c/0x8400
[   11.996371]  tcp_sendmsg+0x4b/0x90
[   11.996572]  inet_sendmsg+0x134/0x2a0
[   11.996823]  __sock_sendmsg+0x265/0x360
[   11.997076]  sock_sendmsg+0x100/0x1e0
[   11.997293]  nvme_tcp_try_send+0x196f/0x6370
[   11.997605]  nvme_tcp_queue_rq+0x1d54/0x20b0
[   11.997882]  blk_mq_dispatch_rq_list+0x5ee/0x2e50
[   11.998175]  __blk_mq_sched_dispatch_requests+0x16dc/0x24a0
[   11.998539]  blk_mq_sched_dispatch_requests+0x11b/0x2c0
[   11.998865]  blk_mq_run_work_fn+0x13b/0x280
[   11.999146]  process_scheduled_works+0x966/0x1ad0
[   11.999465]  worker_thread+0xe44/0x1480
[   11.999709]  kthread+0x53b/0x600
[   11.999927]  ret_from_fork+0x29f/0x7c0
[   12.000191]  ret_from_fork_asm+0x1a/0x30
[   12.000460]
[   12.000558] Uninit was created at:
[   12.000788]  __alloc_frozen_pages_noprof+0x8bf/0xd30
[   12.001096]  alloc_pages_mpol+0x1d0/0x5f0
[   12.001326]  alloc_pages_noprof+0x102/0x290
[   12.001627]  nvme_init_ctrl+0x5a3/0x9f0
[   12.001891]  nvme_tcp_create_ctrl+0xd75/0x19b0
[   12.002170]  nvmf_dev_write+0x4c68/0x4fd0
[   12.002426]  vfs_write+0x587/0x1a10
[   12.002636]  __x64_sys_write+0x207/0x4f0
[   12.002874]  x64_sys_call+0x2ff0/0x3ea0
[   12.003123]  do_syscall_64+0x147/0x3b0
[   12.003400]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   12.003680]
[   12.003777] Bytes 16-2843 of 2844 are uninitialized
[   12.004068] Memory access of size 2844 starts at ffff888109f82000
[   12.004412]
[   12.004530] CPU: 0 UID: 0 PID: 101 Comm: kworker/0:1H Not tainted 7.2.0-rc5-NVMECTL-gf5098b6bae76 #1 PREEMPT(lazy)
[   12.005127] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   12.005762] Workqueue: kblockd blk_mq_run_work_fn
[   12.006073] =====================================================

Allocate the page with __GFP_ZERO.  The single allocation site covers
every use of it: bytes no discard has written stay zero, and bytes one
did write hold that controller's own range list, which it has already
been sent.

The Linux kernel CVE team has assigned CVE-2026-89483 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.5 with commit 530436c45ef2e446c12538a400e465929a0b3ade and fixed in 6.12.109 with commit dc4d4b70a863f7e39ef8bd137634be4e6db8b084
	Issue introduced in 5.5 with commit 530436c45ef2e446c12538a400e465929a0b3ade and fixed in 6.18.50 with commit 67551d8430df94c827e1830bd3a5fae1f66a5219
	Issue introduced in 5.5 with commit 530436c45ef2e446c12538a400e465929a0b3ade and fixed in 7.2.4 with commit f5827817b4fc7feeabf4f53fb4b626e6edc52fef
	Issue introduced in 5.5 with commit 530436c45ef2e446c12538a400e465929a0b3ade and fixed in 7.3-rc1 with commit bededeaaeff404978a5a8e2a605a6c3017cddd3e
	Issue introduced in 4.19.92 with commit ffa56cbdd2409b522b4cb56461bea1c45889417b
	Issue introduced in 5.4.7 with commit 8b0acb768a06083b0d28bace1481c1f6679e76f4

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-89483
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/nvme/host/core.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/dc4d4b70a863f7e39ef8bd137634be4e6db8b084
	https://git.kernel.org/stable/c/67551d8430df94c827e1830bd3a5fae1f66a5219
	https://git.kernel.org/stable/c/f5827817b4fc7feeabf4f53fb4b626e6edc52fef
	https://git.kernel.org/stable/c/bededeaaeff404978a5a8e2a605a6c3017cddd3e