| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
cxl/features: Add check for no entries in cxl_feature_info
cxl EDAC calls cxl_feature_info() to get the feature information and
if the hardware has no Features support, cxlfs may be passed in as
NULL.
[ 51.957498] BUG: kernel NULL pointer dereference, address: 0000000000000008
[ 51.965571] #PF: supervisor read access in kernel mode
[ 51.971559] #PF: error_code(0x0000) - not-present page
[ 51.977542] PGD 17e4f6067 P4D 0
[ 51.981384] Oops: Oops: 0000 [#1] SMP NOPTI
[ 51.986300] CPU: 49 UID: 0 PID: 3782 Comm: systemd-udevd Not tainted 6.17.0dj
test+ #64 PREEMPT(voluntary)
[ 51.997355] Hardware name: <removed>
[ 52.009790] RIP: 0010:cxl_feature_info+0xa/0x80 [cxl_core]
Add a check for cxlfs before dereferencing it and return -EOPNOTSUPP if
there is no cxlfs created due to no hardware support. |
| In the Linux kernel, the following vulnerability has been resolved:
ixgbe: fix too early devlink_free() in ixgbe_remove()
Since ixgbe_adapter is embedded in devlink, calling devlink_free()
prematurely in the ixgbe_remove() path can lead to UAF. Move devlink_free()
to the end.
KASAN report:
BUG: KASAN: use-after-free in ixgbe_reset_interrupt_capability+0x140/0x180 [ixgbe]
Read of size 8 at addr ffff0000adf813e0 by task bash/2095
CPU: 1 UID: 0 PID: 2095 Comm: bash Tainted: G S 6.17.0-rc2-tnguy.net-queue+ #1 PREEMPT(full)
[...]
Call trace:
show_stack+0x30/0x90 (C)
dump_stack_lvl+0x9c/0xd0
print_address_description.constprop.0+0x90/0x310
print_report+0x104/0x1f0
kasan_report+0x88/0x180
__asan_report_load8_noabort+0x20/0x30
ixgbe_reset_interrupt_capability+0x140/0x180 [ixgbe]
ixgbe_clear_interrupt_scheme+0xf8/0x130 [ixgbe]
ixgbe_remove+0x2d0/0x8c0 [ixgbe]
pci_device_remove+0xa0/0x220
device_remove+0xb8/0x170
device_release_driver_internal+0x318/0x490
device_driver_detach+0x40/0x68
unbind_store+0xec/0x118
drv_attr_store+0x64/0xb8
sysfs_kf_write+0xcc/0x138
kernfs_fop_write_iter+0x294/0x440
new_sync_write+0x1fc/0x588
vfs_write+0x480/0x6a0
ksys_write+0xf0/0x1e0
__arm64_sys_write+0x70/0xc0
invoke_syscall.constprop.0+0xcc/0x280
el0_svc_common.constprop.0+0xa8/0x248
do_el0_svc+0x44/0x68
el0_svc+0x54/0x160
el0t_64_sync_handler+0xa0/0xe8
el0t_64_sync+0x1b0/0x1b8 |
| In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix memory leaks when rejecting a non SINGLE data profile without an RST
At the end of btrfs_load_block_group_zone_info() the first thing we do
is to ensure that if the mapping type is not a SINGLE one and there is
no RAID stripe tree, then we return early with an error.
Doing that, though, prevents the code from running the last calls from
this function which are about freeing memory allocated during its
run. Hence, in this case, instead of returning early, we set the ret
value and fall through the rest of the cleanup code. |
| In the Linux kernel, the following vulnerability has been resolved:
comedi: fix divide-by-zero in comedi_buf_munge()
The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits a command with
chanlist_len set to zero, this causes a divide-by-zero error when the device
processes data in the interrupt handler path.
Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.
This prevents potential kernel panics from malformed user commands. |
| In the Linux kernel, the following vulnerability has been resolved:
crypto: rng - Ensure set_ent is always present
Ensure that set_ent is always set since only drbg provides it. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/vmwgfx: Fix a null-ptr access in the cursor snooper
Check that the resource which is converted to a surface exists before
trying to use the cursor snooper on it.
vmw_cmd_res_check allows explicit invalid (SVGA3D_INVALID_ID) identifiers
because some svga commands accept SVGA3D_INVALID_ID to mean "no surface",
unfortunately functions that accept the actual surfaces as objects might
(and in case of the cursor snooper, do not) be able to handle null
objects. Make sure that we validate not only the identifier (via the
vmw_cmd_res_check) but also check that the actual resource exists before
trying to do something with it.
Fixes unchecked null-ptr reference in the snooping code. |
| In the Linux kernel, the following vulnerability has been resolved:
usb: typec: ucsi: fix use-after-free caused by uec->work
The delayed work uec->work is scheduled in gaokun_ucsi_probe()
but never properly canceled in gaokun_ucsi_remove(). This creates
use-after-free scenarios where the ucsi and gaokun_ucsi structure
are freed after ucsi_destroy() completes execution, while the
gaokun_ucsi_register_worker() might be either currently executing
or still pending in the work queue. The already-freed gaokun_ucsi
or ucsi structure may then be accessed.
Furthermore, the race window is 3 seconds, which is sufficiently
long to make this bug easily reproducible. The following is the
trace captured by KASAN:
==================================================================
BUG: KASAN: slab-use-after-free in __run_timers+0x5ec/0x630
Write of size 8 at addr ffff00000ec28cc8 by task swapper/0/0
...
Call trace:
show_stack+0x18/0x24 (C)
dump_stack_lvl+0x78/0x90
print_report+0x114/0x580
kasan_report+0xa4/0xf0
__asan_report_store8_noabort+0x20/0x2c
__run_timers+0x5ec/0x630
run_timer_softirq+0xe8/0x1cc
handle_softirqs+0x294/0x720
__do_softirq+0x14/0x20
____do_softirq+0x10/0x1c
call_on_irq_stack+0x30/0x48
do_softirq_own_stack+0x1c/0x28
__irq_exit_rcu+0x27c/0x364
irq_exit_rcu+0x10/0x1c
el1_interrupt+0x40/0x60
el1h_64_irq_handler+0x18/0x24
el1h_64_irq+0x6c/0x70
arch_local_irq_enable+0x4/0x8 (P)
do_idle+0x334/0x458
cpu_startup_entry+0x60/0x70
rest_init+0x158/0x174
start_kernel+0x2f8/0x394
__primary_switched+0x8c/0x94
Allocated by task 72 on cpu 0 at 27.510341s:
kasan_save_stack+0x2c/0x54
kasan_save_track+0x24/0x5c
kasan_save_alloc_info+0x40/0x54
__kasan_kmalloc+0xa0/0xb8
__kmalloc_node_track_caller_noprof+0x1c0/0x588
devm_kmalloc+0x7c/0x1c8
gaokun_ucsi_probe+0xa0/0x840 auxiliary_bus_probe+0x94/0xf8
really_probe+0x17c/0x5b8
__driver_probe_device+0x158/0x2c4
driver_probe_device+0x10c/0x264
__device_attach_driver+0x168/0x2d0
bus_for_each_drv+0x100/0x188
__device_attach+0x174/0x368
device_initial_probe+0x14/0x20
bus_probe_device+0x120/0x150
device_add+0xb3c/0x10fc
__auxiliary_device_add+0x88/0x130
...
Freed by task 73 on cpu 1 at 28.910627s:
kasan_save_stack+0x2c/0x54
kasan_save_track+0x24/0x5c
__kasan_save_free_info+0x4c/0x74
__kasan_slab_free+0x60/0x8c
kfree+0xd4/0x410
devres_release_all+0x140/0x1f0
device_unbind_cleanup+0x20/0x190
device_release_driver_internal+0x344/0x460
device_release_driver+0x18/0x24
bus_remove_device+0x198/0x274
device_del+0x310/0xa84
...
The buggy address belongs to the object at ffff00000ec28c00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 200 bytes inside of
freed 512-byte region
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec28
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x3fffe0000000040(head|node=0|zone=0|lastcpupid=0x1ffff)
page_type: f5(slab)
raw: 03fffe0000000040 ffff000008801c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 03fffe0000000040 ffff000008801c80 dead000000000122 0000000000000000
head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 03fffe0000000002 fffffdffc03b0a01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff00000ec28b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff00000ec28c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff00000ec28c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff00000ec28d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff00000ec28d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
================================================================
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
remoteproc: qcom: pas: Shutdown lite ADSP DTB on X1E
The ADSP firmware on X1E has separate firmware binaries for the main
firmware and the DTB. The same applies for the "lite" firmware loaded by
the boot firmware.
When preparing to load the new ADSP firmware we shutdown the lite_pas_id
for the main firmware, but we don't shutdown the corresponding lite pas_id
for the DTB. The fact that we're leaving it "running" forever becomes
obvious if you try to reuse (or just access) the memory region used by the
"lite" firmware: The &adsp_boot_mem is accessible, but accessing the
&adsp_boot_dtb_mem results in a crash.
We don't support reusing the memory regions currently, but nevertheless we
should not keep part of the lite firmware running. Fix this by adding the
lite_dtb_pas_id and shutting it down as well.
We don't have a way to detect if the lite firmware is actually running yet,
so ignore the return status of qcom_scm_pas_shutdown() for now. This was
already the case before, the assignment to "ret" is not used anywhere. |
| In the Linux kernel, the following vulnerability has been resolved:
usb: host: max3421-hcd: Fix error pointer dereference in probe cleanup
The kthread_run() function returns error pointers so the
max3421_hcd->spi_thread pointer can be either error pointers or NULL.
Check for both before dereferencing it. |
| In the Linux kernel, the following vulnerability has been resolved:
ext4: fix potential null deref in ext4_mb_init()
In ext4_mb_init(), ext4_mb_avg_fragment_size_destroy() may be called
when sbi->s_mb_avg_fragment_size remains uninitialized (e.g., if groupinfo
slab cache allocation fails). Since ext4_mb_avg_fragment_size_destroy()
lacks null pointer checking, this leads to a null pointer dereference.
==================================================================
EXT4-fs: no memory for groupinfo slab cache
BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 0 P4D 0
Oops: Oops: 0002 [#1] SMP PTI
CPU:2 UID: 0 PID: 87 Comm:mount Not tainted 6.17.0-rc2 #1134 PREEMPT(none)
RIP: 0010:_raw_spin_lock_irqsave+0x1b/0x40
Call Trace:
<TASK>
xa_destroy+0x61/0x130
ext4_mb_init+0x483/0x540
__ext4_fill_super+0x116d/0x17b0
ext4_fill_super+0xd3/0x280
get_tree_bdev_flags+0x132/0x1d0
vfs_get_tree+0x29/0xd0
do_new_mount+0x197/0x300
__x64_sys_mount+0x116/0x150
do_syscall_64+0x50/0x1c0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
==================================================================
Therefore, add necessary null check to ext4_mb_avg_fragment_size_destroy()
to prevent this issue. The same fix is also applied to
ext4_mb_largest_free_orders_destroy(). |
| In the Linux kernel, the following vulnerability has been resolved:
blk-mq: check kobject state_in_sysfs before deleting in blk_mq_unregister_hctx
In __blk_mq_update_nr_hw_queues() the return value of
blk_mq_sysfs_register_hctxs() is not checked. If sysfs creation for hctx
fails, later changing the number of hw_queues or removing disk will
trigger the following warning:
kernfs: can not remove 'nr_tags', no directory
WARNING: CPU: 2 PID: 637 at fs/kernfs/dir.c:1707 kernfs_remove_by_name_ns+0x13f/0x160
Call Trace:
remove_files.isra.1+0x38/0xb0
sysfs_remove_group+0x4d/0x100
sysfs_remove_groups+0x31/0x60
__kobject_del+0x23/0xf0
kobject_del+0x17/0x40
blk_mq_unregister_hctx+0x5d/0x80
blk_mq_sysfs_unregister_hctxs+0x94/0xd0
blk_mq_update_nr_hw_queues+0x124/0x760
nullb_update_nr_hw_queues+0x71/0xf0 [null_blk]
nullb_device_submit_queues_store+0x92/0x120 [null_blk]
kobjct_del() was called unconditionally even if sysfs creation failed.
Fix it by checkig the kobject creation statusbefore deleting it. |
| In the Linux kernel, the following vulnerability has been resolved:
ALSA: pcm: Disable bottom softirqs as part of spin_lock_irq() on PREEMPT_RT
snd_pcm_group_lock_irq() acquires a spinlock_t and disables interrupts
via spin_lock_irq(). This also implicitly disables the handling of
softirqs such as TIMER_SOFTIRQ.
On PREEMPT_RT softirqs are preemptible and spin_lock_irq() does not
disable them. That means a timer can be invoked during spin_lock_irq()
on the same CPU. Due to synchronisations reasons local_bh_disable() has
a per-CPU lock named softirq_ctrl.lock which synchronizes individual
softirq against each other.
syz-bot managed to trigger a lockdep report where softirq_ctrl.lock is
acquired in hrtimer_cancel() in addition to hrtimer_run_softirq(). This
is a possible deadlock.
The softirq_ctrl.lock can not be made part of spin_lock_irq() as this
would lead to too much synchronisation against individual threads on the
system. To avoid the possible deadlock, softirqs must be manually
disabled before the lock is acquired.
Disable softirqs before the lock is acquired on PREEMPT_RT. |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: dont report verifier bug for missing bpf_scc_visit on speculative path
Syzbot generated a program that triggers a verifier_bug() call in
maybe_exit_scc(). maybe_exit_scc() assumes that, when called for a
state with insn_idx in some SCC, there should be an instance of struct
bpf_scc_visit allocated for that SCC. Turns out the assumption does
not hold for speculative execution paths. See example in the next
patch.
maybe_scc_exit() is called from update_branch_counts() for states that
reach branch count of zero, meaning that path exploration for a
particular path is finished. Path exploration can finish in one of
three ways:
a. Verification error is found. In this case, update_branch_counts()
is called only for non-speculative paths.
b. Top level BPF_EXIT is reached. Such instructions are never a part of
an SCC, so compute_scc_callchain() in maybe_scc_exit() will return
false, and maybe_scc_exit() will return early.
c. A checkpoint is reached and matched. Checkpoints are created by
is_state_visited(), which calls maybe_enter_scc(), which allocates
bpf_scc_visit instances for checkpoints within SCCs.
Hence, for non-speculative symbolic execution paths, the assumption
still holds: if maybe_scc_exit() is called for a state within an SCC,
bpf_scc_visit instance must exist.
This patch removes the verifier_bug() call for speculative paths. |
| In the Linux kernel, the following vulnerability has been resolved:
mm: hugetlb: avoid soft lockup when mprotect to large memory area
When calling mprotect() to a large hugetlb memory area in our customer's
workload (~300GB hugetlb memory), soft lockup was observed:
watchdog: BUG: soft lockup - CPU#98 stuck for 23s! [t2_new_sysv:126916]
CPU: 98 PID: 126916 Comm: t2_new_sysv Kdump: loaded Not tainted 6.17-rc7
Hardware name: GIGACOMPUTING R2A3-T40-AAV1/Jefferson CIO, BIOS 5.4.4.1 07/15/2025
pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : mte_clear_page_tags+0x14/0x24
lr : mte_sync_tags+0x1c0/0x240
sp : ffff80003150bb80
x29: ffff80003150bb80 x28: ffff00739e9705a8 x27: 0000ffd2d6a00000
x26: 0000ff8e4bc00000 x25: 00e80046cde00f45 x24: 0000000000022458
x23: 0000000000000000 x22: 0000000000000004 x21: 000000011b380000
x20: ffff000000000000 x19: 000000011b379f40 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000000 x10: 0000000000000000 x9 : ffffc875e0aa5e2c
x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : fffffc01ce7a5c00 x4 : 00000000046cde00 x3 : fffffc0000000000
x2 : 0000000000000004 x1 : 0000000000000040 x0 : ffff0046cde7c000
Call trace:
mte_clear_page_tags+0x14/0x24
set_huge_pte_at+0x25c/0x280
hugetlb_change_protection+0x220/0x430
change_protection+0x5c/0x8c
mprotect_fixup+0x10c/0x294
do_mprotect_pkey.constprop.0+0x2e0/0x3d4
__arm64_sys_mprotect+0x24/0x44
invoke_syscall+0x50/0x160
el0_svc_common+0x48/0x144
do_el0_svc+0x30/0xe0
el0_svc+0x30/0xf0
el0t_64_sync_handler+0xc4/0x148
el0t_64_sync+0x1a4/0x1a8
Soft lockup is not triggered with THP or base page because there is
cond_resched() called for each PMD size.
Although the soft lockup was triggered by MTE, it should be not MTE
specific. The other processing which takes long time in the loop may
trigger soft lockup too.
So add cond_resched() for hugetlb to avoid soft lockup. |
| In the Linux kernel, the following vulnerability has been resolved:
EDAC/i10nm: Skip DIMM enumeration on a disabled memory controller
When loading the i10nm_edac driver on some Intel Granite Rapids servers,
a call trace may appear as follows:
UBSAN: shift-out-of-bounds in drivers/edac/skx_common.c:453:16
shift exponent -66 is negative
...
__ubsan_handle_shift_out_of_bounds+0x1e3/0x390
skx_get_dimm_info.cold+0x47/0xd40 [skx_edac_common]
i10nm_get_dimm_config+0x23e/0x390 [i10nm_edac]
skx_register_mci+0x159/0x220 [skx_edac_common]
i10nm_init+0xcb0/0x1ff0 [i10nm_edac]
...
This occurs because some BIOS may disable a memory controller if there
aren't any memory DIMMs populated on this memory controller. The DIMMMTR
register of this disabled memory controller contains the invalid value
~0, resulting in the call trace above.
Fix this call trace by skipping DIMM enumeration on a disabled memory
controller. |
| In the Linux kernel, the following vulnerability has been resolved:
ASoC: amd/sdw_utils: avoid NULL deref when devm_kasprintf() fails
devm_kasprintf() may return NULL on memory allocation failure,
but the debug message prints cpus->dai_name before checking it.
Move the dev_dbg() call after the NULL check to prevent potential
NULL pointer dereference. |
| In the Linux kernel, the following vulnerability has been resolved:
misc: ocxl: fix possible refcount leak in afu_ioctl()
eventfd_ctx_put need to be called to put the refcount that gotten by
eventfd_ctx_fdget when ocxl_irq_set_handler fails. |
| In the Linux kernel, the following vulnerability has been resolved:
accel/qaic: Fix bootlog initialization ordering
As soon as we queue MHI buffers to receive the bootlog from the device,
we could be receiving data. Therefore all the resources needed to
process that data need to be setup prior to queuing the buffers.
We currently initialize some of the resources after queuing the buffers
which creates a race between the probe() and any data that comes back
from the device. If the uninitialized resources are accessed, we could
see page faults.
Fix the init ordering to close the race. |
| In the Linux kernel, the following vulnerability has been resolved:
pid: Add a judgment for ns null in pid_nr_ns
__task_pid_nr_ns
ns = task_active_pid_ns(current);
pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
if (pid && ns->level <= pid->level) {
Sometimes null is returned for task_active_pid_ns. Then it will trigger kernel panic in pid_nr_ns.
For example:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058
Mem abort info:
ESR = 0x0000000096000007
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x07: level 3 translation fault
Data abort info:
ISV = 0, ISS = 0x00000007, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 39-bit VAs, pgdp=00000002175aa000
[0000000000000058] pgd=08000002175ab003, p4d=08000002175ab003, pud=08000002175ab003, pmd=08000002175be003, pte=0000000000000000
pstate: 834000c5 (Nzcv daIF +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : __task_pid_nr_ns+0x74/0xd0
lr : __task_pid_nr_ns+0x24/0xd0
sp : ffffffc08001bd10
x29: ffffffc08001bd10 x28: ffffffd4422b2000 x27: 0000000000000001
x26: ffffffd442821168 x25: ffffffd442821000 x24: 00000f89492eab31
x23: 00000000000000c0 x22: ffffff806f5693c0 x21: ffffff806f5693c0
x20: 0000000000000001 x19: 0000000000000000 x18: 0000000000000000
x17: 00000000529c6ef0 x16: 00000000529c6ef0 x15: 00000000023a1adc
x14: 0000000000000003 x13: 00000000007ef6d8 x12: 001167c391c78800
x11: 00ffffffffffffff x10: 0000000000000000 x9 : 0000000000000001
x8 : ffffff80816fa3c0 x7 : 0000000000000000 x6 : 49534d702d535449
x5 : ffffffc080c4c2c0 x4 : ffffffd43ee128c8 x3 : ffffffd43ee124dc
x2 : 0000000000000000 x1 : 0000000000000001 x0 : ffffff806f5693c0
Call trace:
__task_pid_nr_ns+0x74/0xd0
...
__handle_irq_event_percpu+0xd4/0x284
handle_irq_event+0x48/0xb0
handle_fasteoi_irq+0x160/0x2d8
generic_handle_domain_irq+0x44/0x60
gic_handle_irq+0x4c/0x114
call_on_irq_stack+0x3c/0x74
do_interrupt_handler+0x4c/0x84
el1_interrupt+0x34/0x58
el1h_64_irq_handler+0x18/0x24
el1h_64_irq+0x68/0x6c
account_kernel_stack+0x60/0x144
exit_task_stack_account+0x1c/0x80
do_exit+0x7e4/0xaf8
...
get_signal+0x7bc/0x8d8
do_notify_resume+0x128/0x828
el0_svc+0x6c/0x70
el0t_64_sync_handler+0x68/0xbc
el0t_64_sync+0x1a8/0x1ac
Code: 35fffe54 911a02a8 f9400108 b4000128 (b9405a69)
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Oops: Fatal exception in interrupt |
| In the Linux kernel, the following vulnerability has been resolved:
x86/kvm: Force legacy PCI hole to UC when overriding MTRRs for TDX/SNP
When running as an SNP or TDX guest under KVM, force the legacy PCI hole,
i.e. memory between Top of Lower Usable DRAM and 4GiB, to be mapped as UC
via a forced variable MTRR range.
In most KVM-based setups, legacy devices such as the HPET and TPM are
enumerated via ACPI. ACPI enumeration includes a Memory32Fixed entry, and
optionally a SystemMemory descriptor for an OperationRegion, e.g. if the
device needs to be accessed via a Control Method.
If a SystemMemory entry is present, then the kernel's ACPI driver will
auto-ioremap the region so that it can be accessed at will. However, the
ACPI spec doesn't provide a way to enumerate the memory type of
SystemMemory regions, i.e. there's no way to tell software that a region
must be mapped as UC vs. WB, etc. As a result, Linux's ACPI driver always
maps SystemMemory regions using ioremap_cache(), i.e. as WB on x86.
The dedicated device drivers however, e.g. the HPET driver and TPM driver,
want to map their associated memory as UC or WC, as accessing PCI devices
using WB is unsupported.
On bare metal and non-CoCO, the conflicting requirements "work" as firmware
configures the PCI hole (and other device memory) to be UC in the MTRRs.
So even though the ACPI mappings request WB, they are forced to UC- in the
kernel's tracking due to the kernel properly handling the MTRR overrides,
and thus are compatible with the drivers' requested WC/UC-.
With force WB MTRRs on SNP and TDX guests, the ACPI mappings get their
requested WB if the ACPI mappings are established before the dedicated
driver code attempts to initialize the device. E.g. if acpi_init()
runs before the corresponding device driver is probed, ACPI's WB mapping
will "win", and result in the driver's ioremap() failing because the
existing WB mapping isn't compatible with the requested WC/UC-.
E.g. when a TPM is emulated by the hypervisor (ignoring the security
implications of relying on what is allegedly an untrusted entity to store
measurements), the TPM driver will request UC and fail:
[ 1.730459] ioremap error for 0xfed40000-0xfed45000, requested 0x2, got 0x0
[ 1.732780] tpm_tis MSFT0101:00: probe with driver tpm_tis failed with error -12
Note, the '0x2' and '0x0' values refer to "enum page_cache_mode", not x86's
memtypes (which frustratingly are an almost pure inversion; 2 == WB, 0 == UC).
E.g. tracing mapping requests for TPM TIS yields:
Mapping TPM TIS with req_type = 0
WARNING: CPU: 22 PID: 1 at arch/x86/mm/pat/memtype.c:530 memtype_reserve+0x2ab/0x460
Modules linked in:
CPU: 22 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.16.0-rc7+ #2 VOLUNTARY
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/29/2025
RIP: 0010:memtype_reserve+0x2ab/0x460
__ioremap_caller+0x16d/0x3d0
ioremap_cache+0x17/0x30
x86_acpi_os_ioremap+0xe/0x20
acpi_os_map_iomem+0x1f3/0x240
acpi_os_map_memory+0xe/0x20
acpi_ex_system_memory_space_handler+0x273/0x440
acpi_ev_address_space_dispatch+0x176/0x4c0
acpi_ex_access_region+0x2ad/0x530
acpi_ex_field_datum_io+0xa2/0x4f0
acpi_ex_extract_from_field+0x296/0x3e0
acpi_ex_read_data_from_field+0xd1/0x460
acpi_ex_resolve_node_to_value+0x2ee/0x530
acpi_ex_resolve_to_value+0x1f2/0x540
acpi_ds_evaluate_name_path+0x11b/0x190
acpi_ds_exec_end_op+0x456/0x960
acpi_ps_parse_loop+0x27a/0xa50
acpi_ps_parse_aml+0x226/0x600
acpi_ps_execute_method+0x172/0x3e0
acpi_ns_evaluate+0x175/0x5f0
acpi_evaluate_object+0x213/0x490
acpi_evaluate_integer+0x6d/0x140
acpi_bus_get_status+0x93/0x150
acpi_add_single_object+0x43a/0x7c0
acpi_bus_check_add+0x149/0x3a0
acpi_bus_check_add_1+0x16/0x30
acpi_ns_walk_namespace+0x22c/0x360
acpi_walk_namespace+0x15c/0x170
acpi_bus_scan+0x1dd/0x200
acpi_scan_init+0xe5/0x2b0
acpi_init+0x264/0x5b0
do_one_i
---truncated--- |
