| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: hyper-v: Clamp stimer deadline to avoid livelock
Fix an issue where userspace or the guest can program an Hyper-V
synthetic timer to have a deadline in the past via integer overflow,
preventing the CPU from making progress and triggering an RCU stall.
Hyper-V's SynIC exposes 4 per-vCPU synthetic timers to the
guest, which are emulated by KVM. Each is programmed through the
HV_X64_MSR_STIMERi_CONFIG and HV_X64_MSR_STIMERi_COUNT MSRs. Depending
on CONFIG, COUNT represents either the absolute expiration time or the
period of a periodic timer, both expressed in 100ns ticks. These timers
may be set both by the guest (WRMSR) and the host (KVM_SET_MSRS).
When the timer is enabled, stimer_start() translates COUNT to an
absolute monotonic deadline and arms an hrtimer. If COUNT is set to a
value close to U64_MAX, the deadline calculation can overflow.
ktime_add_ns(ktime_now, 100 * (stimer->exp_time - time_now))
This can result in a CPU livelock. stimer_start() arms the timer
via hrtimer_start() with a deadline in the past, which causes it to
immediately fire. The stimer callback then raises KVM_RQ_HV_STIMER, with
the intention of causing KVM to deliver a synthetic interrupt on the
next vCPU guest enter.
Then, once userspace issues KVM_RUN, vcpu_enter_guest() consumes the
request, calling kvm_hv_process_stimers(). This would normally disable
the timer via stimer_expiration() once the deadline is in the past.
However, the deadline comparison is done between the KVM reference
counter and stime->exp_time, which is a big value close to U64_MAX, so
this never happens for a few thousand years.
kvm_hv_process_timers() then re-arms the timer via stimer_start(), since
it was not disabled, which again fires immediately. Before entering
the guest, kvm_vcpu_exit_request() checks kvm_request_pending(),
which returns true due to the newly raised KVM_REQ_HV_STIMER. Then
vcpu_enter_guest() aborts the guest entry, returning early into
vcpu_run(), which loops back again into vcpu_enter_guest(), restarting
the cycle.
Since there are no manual yields in this loop, a task with SCHED_FIFO
may starve RCU grace-period kthreads, which exposes the stalls found
by syzcaller:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: (detected by 1, t=10502 jiffies, g=14269, q=1142 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10500 (4294965239-4294954739), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10500 jiffies! g14269 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
( ... )
Call Trace:
<IRQ>
__run_hrtimer kernel/time/hrtimer.c:1773 [inline]
__hrtimer_run_queues+0x408/0xc30 kernel/time/hrtimer.c:1841
hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1903
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
__sysvec_apic_timer_interrupt+0x102/0x3e0 arch/x86/kernel/apic/apic.c:1062
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1056
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa8/0x110 kernel/locking/spinlock.c:194
Code: 74 05 e8 0b f4 5f f6 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4f f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 23 6b 27 f6 65 8b 05 7c 60 5a 07 85 c0 74 40 48 c7 04 24 0e 36
RSP: 0018:ffffc900040a7320 EFLAGS: 00000206
RAX: 5de15cb931505900 RBX: 0000000000000a06 RCX: 5de15cb931505900
RDX: 0000000000000007 RSI: ffffffff8daa9dc3 RDI: 0000000000000001
RBP: ffffc900040a73b0 R08: ffffffff8fc3d0
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: x86/mmu: Consume the locked rmap value in the lockless rmap walk
__kvm_rmap_lock() deliberately elides the rmap lock when it observes an
empty rmap. In that case kvm_rmap_lock_readonly() also re-enables
preemption and returns zero, so the caller holds neither the rmap lock
nor a preemption reference. The elision documents the invariant it
relies on:
* Elide the lock if the rmap is empty, as lockless walkers (read-only
* mode) don't need to (and can't) walk an empty rmap, nor can they add
* entries to the rmap. I.e. the only paths that process empty rmaps
* do so while holding mmu_lock for write, and are mutually exclusive.
kvm_rmap_age_gfn_range() ignores the returned value and unconditionally
enters for_each_rmap_spte_lockless(). The iterator started with
rmap_get_first(), which re-reads rmap_head->val rather than using the
value returned by the lock. If a writer populates the rmap between the
lock's read and the iterator's re-read, the aging path walks the newly
installed rmap without holding its lock.
For a KVM_RMAP_MANY rmap this leaves the walker following a
pte_list_desc chain that it never locked. A writer holding mmu_lock for
write may free that chain (e.g. kvm_zap_all_rmap_sptes() on the recycle
path, or any rmap zap) via kmem_cache_free() while the walk is in
progress, giving a slab use-after-free. Nothing serialises the two: the
aging path runs without mmu_lock when CONFIG_KVM_MMU_LOCKLESS_AGING=y,
and the rmap lock that would otherwise exclude the writer was elided.
Because the empty path re-enables preemption, the interval between the
two reads can span an arbitrary scheduling delay.
Fix the class of bug by having the lockless walk consume the value
returned by the lock instead of re-reading the rmap. Split
rmap_get_first() into __rmap_get_first(), which starts an iterator from
an already-read rmap value, and make for_each_rmap_spte_lockless() take
that value and call __rmap_get_first() directly.
kvm_rmap_age_gfn_range() passes the value returned by
kvm_rmap_lock_readonly(): when the lock was elided the value is zero,
__rmap_get_first() returns NULL, and the walk is skipped. No lockless
walker re-reads the rmap, so the lock-elision invariant cannot be
violated, and no lock()-without-paired-unlock() path is added to the
aging code. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: nVMX: Service local TLB flushes on failed nested VM-Enter
KVM services local TLB flushes on "full" nested VM-Exits (through
__nested_vmx_vmexit()), but not if a nested VM-Enter fails (e.g. due to
failed VMCS checks in nested_vmx_enter_non_root_mode()).
However, it is possible that KVM had queued TLB flushes that need to be
performed, even if the nested VM-Enter was not successful. For example,
if VPID is disabled for L2 (via nested_vmx_transition_tlb_flush(), or if
via the MSR load lists, as the SDM says:
If any MSR is being loaded in such a way that would architecturally
require a TLB flush, the TLBs are updated so that, after VM entry, the
logical processor will not use any translations that were cached before
the transition.
The SDM is unclear about when the TLB flush should occur, and whether or
not a failed VM entry would flush the TLB, so it is safer to always
do the TLB flush in this case.
More concretely, KVM also updates the last VPID L1 used for L2 in
nested_vmx_transition_tlb_flush() (i.e. last_vpid), even if the VM entry
ultimately fails. With the current code, KVM could miss a TLB flush if
L1 changes L2's VPID, then does a failed VM entry followed by a
successful one, as the failed VM entry would update last_vpid but not
actually flush the TLB. Servicing local TLB flushes on failed VM entries
makes sure that the TLB is always flushed when last_vpid is updated. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: nVMX: Ensure KVM_REQ_GET_NESTED_STATE_PAGES is cleared on VM-Exit
Always check and clear KVM_REQ_GET_NESTED_STATE_PAGES when emulating a
nested VM-Exit to ensure the request is cleared, even when KVM was built
with CONFIG_KVM_HYPERV=n, as KVM subtly relies on the "check" to clear
the flag and thus avoid double-mapping the vmcs12 pages, e.g. if KVM
manages to bail from VM-Enter without processing the request, and then
emulates VMLAUNCH or VMRESUME. |
| In the Linux kernel, the following vulnerability has been resolved:
iio: light: ltrf216a: fix runtime PM reference leak in error path
ltrf216a_get_lux() acquires a runtime PM reference by calling
ltrf216a_set_power_state(data, true). However, if
ltrf216a_read_data() fails, the function returns immediately without
dropping the reference.
This leaves the runtime PM usage count unbalanced, preventing the device
from autosuspending after a failed read.
Fix this by releasing the runtime PM reference before returning from the
error path. |
| In the Linux kernel, the following vulnerability has been resolved:
iio: light: apds9306: fix PM reference leak in apds9306_read_data()
apds9306_read_data() calls pm_runtime_resume_and_get() but several
error paths return directly without calling pm_runtime_put_autosuspend(),
leaking the runtime PM reference and preventing the device from
autosuspending.
Use PM_RUNTIME_ACQUIRE_AUTOSUSPEND() and PM_RUNTIME_ACQUIRE_ERR() to
automatically handle runtime PM reference release on all return paths. |
| In the Linux kernel, the following vulnerability has been resolved:
iio: chemical: atlas-sensor: use iio_trigger_poll_nested() to fix remove UAF
The atlas driver requests its hardware data-ready IRQ with
devm_request_threaded_irq(); its threaded handler queues an irq_work,
atlas_work_handler(), that calls iio_trigger_poll(data->trig).
The IRQ is devm-managed, so free_irq() runs from the devres unwind after
atlas_remove() returns without flushing that irq_work. Once a buffer is
enabled, conversion-complete IRQs keep firing and queueing it; a pending
irq_work can therefore run after the unwind has freed atlas_data/indio_dev
and the trigger, when atlas_work_handler() derives the atlas_data pointer
via container_of() and dereferences data->trig, a use-after-free.
Call iio_trigger_poll_nested() directly from the threaded handler instead
of bouncing through irq_work. free_irq() then drains the threaded handler,
closing the window; other iio drivers with a threaded data-ready IRQ do the
same (e.g. bmi270).
This issue was found by an in-house static analysis tool. |
| In the Linux kernel, the following vulnerability has been resolved:
iio: buffer: Fix potential use-after-free in anonymous buffer release
An anonymous buffer handle holds a reference to the underlying IIO device.
The reference is dropped in the buffer handle's release function. If the
device has been removed, either through unbind or hot-unplug, the buffer
handle might hold the last reference.
The release function takes the mutex for the buffer using a guard, which
means the unlock happens after all the code in the function, including
`iio_device_put()`. If the anonymous buffer holds the last reference this
might free both the IIO device and the buffer, which contains the mutex,
leading to use-after-free when the mutex is unlocked.
Fix this by using a scoped guard just around the buffer dmabuf list access,
making sure the mutex is unlocked before releasing the IIO device.
Version 10 of the patch that introduced this issue used this exact scheme
of first unlocking and then dropping the reference [1]. During review it
was suggested to use a guard instead, and version 11 made that change [2]. |
| In the Linux kernel, the following vulnerability has been resolved:
clk: meson: align gxbb_32k_clk_sel number of parents with actual count
The following out-of-bounds read has been observed by Christian on a
GXBB WeTek Hub:
==================================================================
BUG: KASAN: global-out-of-bounds in __clk_register+0x1b70/0x2418
Read of size 8 at addr ffffd66320cf88e0 by task swapper/0/1
CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-rc5 #1 PREEMPT
Hardware name: WeTek Hub (DT)
Call trace:
show_stack+0x14/0x20 (C)
dump_stack_lvl+0x74/0x94
print_report+0x164/0x4b0
kasan_report+0x98/0xd8
__asan_report_load8_noabort+0x1c/0x24
__clk_register+0x1b70/0x2418
devm_clk_hw_register+0x74/0x15c
meson_clkc_init+0xd4/0x20c
meson_clkc_syscon_probe+0x5c/0x94
platform_probe+0xbc/0x17c
really_probe+0x184/0x844
__driver_probe_device+0x154/0x35c
driver_probe_device+0x60/0x188
__driver_attach+0x168/0x4a0
bus_for_each_dev+0xec/0x180
driver_attach+0x38/0x58
bus_add_driver+0x238/0x4c0
driver_register+0x150/0x388
__platform_driver_register+0x54/0x7c
gxbb_clkc_driver_init+0x18/0x20
do_one_initcall+0xb8/0x340
kernel_init_freeable+0x49c/0x52c
kernel_init+0x24/0x148
ret_from_fork+0x10/0x20
The buggy address belongs to the variable:
gxbb_32k_clk_parents+0x60/0x400
The buggy address belongs to a vmalloc virtual mapping
The buggy address belongs to the physical page:
Memory state around the buggy address:
ffffd66320cf8780: 00 00 00 00 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
ffffd66320cf8800: 00 04 f9 f9 f9 f9 f9 f9 00 04 f9 f9 f9 f9 f9 f9
>ffffd66320cf8880: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9
^
ffffd66320cf8900: 00 01 f9 f9 f9 f9 f9 f9 00 06 f9 f9 f9 f9 f9 f9
ffffd66320cf8980: 00 00 02 f9 f9 f9 f9 f9 00 00 02 f9 f9 f9 f9 f9
==================================================================
Commit 7915d7d5407c ("clk: amlogic: gxbb: drop non existing 32k clock
parent") dropped a non-existing clock parent from the gxbb_32k_clk_sel
mux but didn't adjust the hard-coded num_parents field. Fix the actual
number of parents of that mux by using ARRAY_SIZE instead (avoiding
similar problems in future). |
| In the Linux kernel, the following vulnerability has been resolved:
batman-adv: bla: fix freeing of claims on meshif deletion
When the mesh interface is getting deleted, then
batadv_bla_del_backbone_claims() (via batadv_bla_purge_backbone_gw()) could
make sure that all claims gets removed. But this function is only executed
when bat_priv->bla.claim_hash is not NULL. And since batadv_bla_free() is
always setting it to NULL before it is (indirectly) called, it was never
actually executed.
But the batadv_bla_purge_claims() -> batadv_handle_unclaim() is at the
moment too fragile because the BLA code is not handling the rehashing in
batadv_bla_update_orig_address(). The stored backbone address doesn't have
to be the one actually used for the hash bucket selection during the
initial adding of the backbone. The batadv_handle_unclaim() can therefore
fail to find the respective backbone for the unclaim and then stop the
deletion.
But the actual backbone_gw object is not needed for the unclaim because all
relevant information is always provided by the caller. And the check for
the existence of the backbone_gw doesn't provide any additional security
check for the deletion of a claim. |
| In the Linux kernel, the following vulnerability has been resolved:
batman-adv: dat: avoid unaligned fault in IP extraction
Independent of the alignment of the ARP packet in the SKB, either the
batadv_arp_ip_src or the batadv_arp_ip_dst will have an unaligned access
(on HW without native unaligned read support).
Use get_unaligned() to handle this properly on all architectures. |
| In the Linux kernel, the following vulnerability has been resolved:
batman-adv: fix stale receive device on merged fragments
Fragment reassembly reuses the skb from the highest-numbered buffered
fragment as the merged packet. When that fragment was received on a hard
interface which is deleted before the chain completes, the merged skb can
re-enter the receive path with a stale skb->dev and skb_iif.
batadv_batman_skb_recv() passes such merged packets through the normal
receive handlers again. DAT and bridge loop avoidance both derive the ARP
header length from skb->dev, so they can dereference the freed net_device
before the packet reaches the local mesh interface.
Refresh the receive device metadata from the current receive device before
running the packet handlers. This keeps internally reinjected merged
fragments consistent with the normal receive path after hard interface
teardown. |
| In the Linux kernel, the following vulnerability has been resolved:
ftrace: Take trace_array reference before accessing its ftrace_ops
The trace instance files set_ftrace_filter and set_ftrace_notrace was
updated to work with specific trace instances (trace_arrays). The issue is
that when these files are opened, there is a small race window where it
will use the ftrace_ops from the inode->private pointer to get a reference
to the trace_array and then take its reference. The problem is that the
ftrace_ops itself could be freed. If the rmdir on the instance happens at
the same time the set_ftrace_filter file is opened, the rmdir could have
also freed the ftrace_ops and referencing it will cause a use-after-free
bug and crash the kernel.
Instead, pass in the trace_array as the file private data (NULL for the
top level instance), and then pass both the trace_array and the ftrace_ops
to the ftrace_regex_open() function. If the trace_array is NULL, then it
just uses the ftrace_ops without the need to take its reference (like
normal). If the ftrace_ops is NULL, that is only the case for the top
level instance and the global_ops can be used.
This allows the trace_array to have its reference incremented before
touching the ftrace_ops that could also be freed when the instance is. |
| In the Linux kernel, the following vulnerability has been resolved:
futex: Prevent rcuwait use-after-free during requeue PI
On PREEMPT_RT, FUTEX_CMP_REQUEUE_PI can trigger a KASAN report
(slab-out-of-bounds) in futex_requeue_pi_complete() invocation of
rcuwait_wake_up().
The futex_q used by futex_wait_requeue_pi() is allocated on the waiter's
stack. An early wakeup can race with a PI requeue as follows:
waiter requeue task
------ ------------
futex_wait_requeue_pi()
futex_do_wait()
schedule()
futex_requeue
futex_proxy_trylock_atomic()
futex_requeue_pi_prepare()
Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_IN_PROGRESS
* timeout/ signal wakes waiter *
futex_requeue_pi_wakeup_sync()
Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_WAIT
requeue_pi_wake_futex
futex_requeue_pi_complete()
cmpxchg Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_LOCKED
rcuwait_wait_event()
if (atomic_read(&q->requeue_state) != Q_REQUEUE_PI_WAIT)
break /* no schedule() */
/* q.pi_state->owner == current */
futex_private_hash_put()
/* return from syscall */
rcuwait_wake_up(&q->requeue_wait)
/* q is gone */
futex_requeue_pi_complete() publishes Q_REQUEUE_PI_LOCKED before
calling rcuwait_wake_up(). The waiter observes this state in
rcuwait_wait_event() before invoking schedule() in rcuwait_wait_event().
Here, the waiter is free leave the syscall before requeue task can
complete the wake.
To address this race skip rcuwait_wake_up() in the Q_REQUEUE_PI_LOCKED
case.
This state is only published by requeue_pi_wake_futex(), which saves
q->task before futex_requeue_pi_complete() and wakes the waiter via
wake_up_state().
This wake is intended to wake the waiter from its futex_do_wait() sleep.
If the waiter is still sleeping there, it can not get into the
Q_REQUEUE_PI_WAIT state (and require this removed wake).
Should the waiter be woken up from futex_do_wait() by other means (as in
this example) and sleep in futex_requeue_pi_wakeup_sync() then the
wake_up_state() from requeue_pi_wake_futex() will wake it, too.
Should the waiter task terminate before wake_up_state() had a chance to
wake the task then the task pointer does not become invalid because the
futex_hash_bucket::lock is held and the task pointer is RCU protected.
[bigeasy: Updated comment and commit message] |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: bsg: Fix TOCTOU in io_uring passthrough command setup
scsi_bsg_uring_cmd() reads bsg_uring_cmd from the shared mmap'd SQE.
Userspace can change a field after we check it and before we use it.
request_len is the sharp case: it can grow past sizeof(scmd->cmnd) after
the bound check and overflow scmd->cmnd in copy_from_user().
READ_ONCE() the SQE fields we check or use into locals before use. |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: target: iscsi: Reserve a terminator byte for the login payload
iscsi_target_check_login_request() rejects a login PDU whose
DataSegmentLength exceeds MAX_KEY_VALUE_PAIRS, but the test is '>' and
login->req_buf is allocated with exactly MAX_KEY_VALUE_PAIRS
bytes. Since iscsit_get_login_rx() receives payload_length + padding
bytes, where
padding = ((-payload_length) & 3);
any payload_length from 8189 to 8192 fills the whole 8192 byte
buffer. The write stays in bounds, but no byte is left for a NUL
terminator.
The buffer is subsequently consumed as a C string. In the CHAP path
chap_check_algorithm() calls kstrdup(a_str), and extract_param() calls
strstr(in_buf, pattern) followed by strlen_semi(), none of which take a
length. convert_null_to_semi() additionally rewrites every embedded NUL
to ';', so even a payload made of well formed NUL separated key=value
records is left without a terminator. These walk past the end of the
object into adjacent slab memory. It is reachable by an unauthenticated
initiator against a portal configured for CHAP; when authentication is
not required iscsi_login_zero_tsih_s2() rewrites AuthMethod to None and
the CHAP path is never entered.
Allocate one extra byte. kzalloc() zeroes it and nothing ever writes to
it, as every writer copies to offset 0 for at most MAX_KEY_VALUE_PAIRS
bytes, so the buffer is always terminated. |
| In the Linux kernel, the following vulnerability has been resolved:
spi: Fix DMA mapping ownership on partial map failure
If RX mapping fails after TX mapping succeeds, __spi_map_msg() unmaps
TX but leaves tx_sg_mapped set. If TX mapping fails on a later
transfer, mappings created for earlier transfers remain active.
In both cases, cur_{tx,rx}_dma_dev have not yet been updated because they
are assigned only after every transfer has been mapped. The subsequent
spi_unmap_msg() may therefore unmap the TX mapping again or release
earlier mappings using a NULL or stale device. Using a NULL device can
trigger an oops. An empty SG table does not prevent the NULL dereference
because dma_unmap_sg_attrs() accesses the device before checking the
entry count.
Publish both mapping devices before mapping starts and unwind all
failures through __spi_unmap_msg(). This clears the mapping flags and
releases each mapping once with the device that created it.
Publishing the devices before the loop also refreshes them when no
transfer needs mapping. No mapping flag is set in that case, so current
users do not use the pointers as mapping owners. |
| In the Linux kernel, the following vulnerability has been resolved:
mtd: mtdoops: free page bitmap when the backing MTD is removed
mtdoops_notify_add() allocates oops_page_used when the configured MTD
device is registered. mtdoops_notify_remove() detaches from that device
but leaves the bitmap allocated. If the same MTD device is later
registered again, the add path allocates a new bitmap and overwrites the
old pointer, leaking one vmalloc allocation per remove/add cycle.
This is only visible when the backing MTD device can disappear and be
registered again while mtdoops remains loaded, so the usual static MTD
case does not expose it.
Free the bitmap after unregistering the dumper and flushing the pending
workers, then clear the pointer and page count before a later attach can
allocate fresh state. Clearing the pointer also keeps the module exit
path from freeing the same bitmap a second time after a remove event. |
| In the Linux kernel, the following vulnerability has been resolved:
s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects
In order to traverse or add/remove ap_matrix_mdev objects in the
matrix_dev->mdev_list, the matrix_dev->guests_lock mutex must be held.
There are two functions that access the list without holding the mutex:
vfio_ap_mdev_probe function
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The vfio_ap_mdev_probe function uses the matrix_dev->mdevs_lock
mutex to guard the add of a newly created ap_matrix_mdev object to the
matrix_dev->mdev_list. This mutex does not protect list access; its purpose
is to guard against concurrent access to fields contained in an
ap_matrix_mdev object. This could lead to kernel memory corruption or
use-after-free if another mdev is created or removed concurrently.
The adding of an ap_matrix_mdev object to matrix_dev->mdev_list
is now guarded by the matrix_dev->guests_lock which is the correct
way to protect against concurrent mdev_list access.
Also removed the following two lines of code because the matrix_mdev is
allocated via vfio_alloc_device macro which uses kzalloc, so req_trigger
and cfg_chg_trigger are already zero-initialised when the struct is
allocated before the call to vfio_register_emulated_iommu_dev. This
prevents a window whereby these triggers are set to NULL after
the device is exposed to userspace.
matrix_mdev->req_trigger = NULL;
matrix_mdev->cfg_chg_trigger = NULL;
vfio_ap_mdev_for_queue function
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The status_show function that supports display of the status attribute of
the devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue
function which iterates the matrix_dev->mdev_list to find the object
representing the queue device whose status is to be displayed. In order to
traverse this list, the matrix_dev->guests_lock mutex must be held.
To fix this, the guests_lock mutex is taken prior to taking the
matrix_dev->mdevs_lock mutex in the status_show function. It is taken
there rather than the vfio_ap_mdev_for_queue function - where it is
needed - because it must be taken prior to the mdevs_lock mutex in order to
adhere to the proper locking order and prevent a lockdep splat; also
because the mdevs_lock is needed there to access fields within
the matrix_mdev object in that function.
See the vfio-ap-locking.rst in the linux kernel tree. |
| In the Linux kernel, the following vulnerability has been resolved:
s390/vfio-ap: Fix control domain removal in vfio_ap_mdev_cfg_remove
The vfio_ap_config_remove function uses the bitmap_andnot function to clear
bits from the matrix_mdev->matrix.adm bitmap (specifies the control domains
assigned to the mdev). This prevents the explicitly unplugged control
domains from being removed the KVM guest. The bitmap_and function is used
instead. |
