| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: dummy_hcd: prevent fifo_req reuse during giveback
dummy_hcd embeds a single shared usb_request (dum->fifo_req) that the
"emulated single-request FIFO" fast-path in dummy_queue() reuses for
small IN transfers: it copies the caller's request into it
(req->req = *_req) and queues it, treating list_empty(&fifo_req.queue)
as "the slot is free".
The completion side (dummy_timer/transfer/nuke/dummy_dequeue) follows
the standard pattern: list_del_init(&req->queue) unlinks the request,
then the lock is dropped and usb_gadget_giveback_request() invokes
req->complete(). But list_del_init() makes fifo_req.queue look empty
*before* the completion callback returns, so a concurrent dummy_queue()
on another CPU sees the slot as free, reuses fifo_req and runs
req->req = *_req -- overwriting req->complete while dummy_timer is
mid-calling it. The indirect call then jumps to a clobbered pointer,
causing a general protection fault / page fault in dummy_timer
(syzkaller extid faf3a6cf579fc65591ca). The clobbering write is an
in-bounds memcpy on a live shared object, so KASAN cannot flag it.
Add a fifo_req_busy bit covering the shared request's whole lifetime:
set it in dummy_queue() when the FIFO fast-path takes fifo_req (making
it the fast-path guard, replacing the list_empty(&fifo_req.queue)
test), and clear it after the completion callback has returned, via a
dummy_giveback() helper used at all four gadget-request giveback
sites. The shared slot can no longer be reused until its completion
callback has finished. |
| The UpdateHub management subsystem (subsys/mgmt/updatehub/updatehub.c) drives every update operation through a single file-scope ctx structure that holds the CoAP block context, payload buffer, status code, socket, and a one-element poll-fd array fds[1]. Access to ctx was not serialized, and prepare_fds() wrote ctx.fds[ctx.nfds] and incremented ctx.nfds with no bounds check.
Two independent paths mutate ctx concurrently: the background autohandler running on the system workqueue, and user-triggered operations reached through the updatehub run shell command, direct API calls, or — since the operations are exposed as syscalls — userspace threads. When a second flow enters prepare_fds() while ctx.nfds is already 1, the write lands one element past the array; by struct layout it overlaps the adjacent ctx.sock/ctx.nfds members. More broadly, the unsynchronized sharing lets two flows interleave connection setup and teardown, double-closing a socket descriptor or scribbling the shared buffers.
The result is corruption of the update subsystem's internal state and denial of service of the firmware-update path; the out-of-bounds write is contained within the ctx structure and there is no demonstrated path to memory outside it or to code execution. Triggering requires a local actor able to invoke update operations (or, with CONFIG_USERSPACE, an unprivileged userspace thread) and to win a timing race against the background handler; remote peers cannot control the race timing. The fix serializes the entry points with a mutex and adds a bounds check to prepare_fds(). |
| In the Linux kernel, the following vulnerability has been resolved:
drm/xe/guc: Hold device ref until queue teardown completes
GuC exec queue destruction can run asynchronously. If the final device
put happens from a destroy worker, drmm cleanup can end up draining
the same workqueue and deadlock.
Hold a drm_device reference for the queue lifetime and drop it after
queue teardown completes. This keeps drmm cleanup from running while
async destroy work is still pending.
Move GuC destroy work to a module-lifetime Xe workqueue and flush it
on PCI remove so hot-unbind/rebind still waits for pending destroy work.
With queue-held device refs, guc_submit_sw_fini() cannot run with live
GuC IDs. Replace the fini wait with an assertion and remove the unused
fini_wq.
v2:
- Rebase
v3:
- Switch to queue-lifetime drm_dev_get()/drm_dev_put() model. (Matt)
- Queue async teardown on system_dfl_wq instead of xe->destroy_wq. (Matt)
- Drop separate deferred drm_dev_put worker.
- Remove stale drain_workqueue(xe->destroy_wq) from guc_submit_sw_fini().
v4:
- Replace the guc_submit_sw_fini() wait with an assertion and remove
the now-unused fini_wq. (sashiko)
v5:
- Move destroy work to a module-lifetime Xe workqueue instead of
system_dfl_wq. (Matt)
- Flush the module-lifetime destroy workqueue during PCI remove to
preserve the old device-remove wait semantics.
v6:
- Keep SVM pagemap destroy work on the per-device destroy_wq to avoid
letting it outlive the xe_device/drm_device. (Sashiko)
- Use WQ_MEM_RECLAIM for xe->destroy_wq because SVM pagemap destroy work
can be queued from the reclaim path.
v7:
- Drop the per-device xe->destroy_wq and use the module-level destroy WQ
for SVM pagemap destroy as well. (Matt)
- Rename xe_exec_queue_destroy_wq_*() helpers to xe_destroy_wq_*()
helpers because the WQ is no longer exec-queue specific. (Matt)
v8:
- Rebase.
v9:
- Keep SVM pagemap destroy work on the per-device WQ_MEM_RECLAIM
destroy_wq because it can be queued from reclaim and embeds
the dev_pagemap used by devres teardown. (Sashiko)
- Keep the module-level destroy WQ GuC-only and drop WQ_MEM_RECLAIM
from it.
- Update the module-WQ kdoc to document the GuC/SVM split.
v10:
- Keep xe->destroy_wq per-cpu while adding WQ_MEM_RECLAIM to fix the
workqueue allocation warning.
v11:
- Drop the SVM pagemap destroy comment as it was revision-specific.
(Thomas)
v12:
- Rebase.
(cherry picked from commit da1124abac689cc2b1d8995e5f0a816f8a122edb) |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: free AP_VLAN bc_buf SKBs outside IRQ lock
ieee80211_do_stop() removes AP_VLAN packets from the parent AP
ps->bc_buf while holding ps->bc_buf.lock with IRQs disabled. It then
calls ieee80211_free_txskb() before dropping the lock.
ieee80211_free_txskb() is not just a passive SKB release. For SKBs with
TX status state it can report a dropped frame through cfg80211/nl80211,
and that path can reach netlink tap transmit. This is the same reason
the pending queue cleanup in ieee80211_do_stop() already unlinks SKBs
under the queue lock and frees them after IRQ state is restored.
The buggy scenario involves two paths, with each column showing the
order within that path:
AP_VLAN management TX: AP_VLAN stop:
1. attach ACK-status state 1. clear the running state
2. queue a multicast SKB on 2. take ps->bc_buf.lock with IRQs
parent ps->bc_buf disabled
3. unlink the AP_VLAN SKB
4. call ieee80211_free_txskb()
Unlink matching AP_VLAN SKBs from ps->bc_buf under the existing lock,
but move them to a local free queue. Drop the lock and restore IRQ state
before calling ieee80211_free_txskb().
WARNING: kernel/softirq.c:430 at __local_bh_enable_ip |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: cfg80211: convert pmsr_free_wk to wiphy_work to fix deadlock
When a netlink socket that owns a PMSR session is closed,
cfg80211_release_pmsr() clears the request's nl_portid and queues
pmsr_free_wk to call cfg80211_pmsr_process_abort() asynchronously.
If the interface tears down concurrently, cfg80211_pmsr_wdev_down()
is called under wiphy_lock and calls cancel_work_sync(&pmsr_free_wk)
to wait for any running work. The work function acquires wiphy_lock
via guard(wiphy) before calling process_abort.
This is a deadlock: wdev_down holds wiphy_lock and blocks inside
cancel_work_sync(); pmsr_free_wk blocks trying to acquire that same
wiphy_lock. Neither thread can proceed.
The same deadlock is reachable from cfg80211_leave_locked(), which
calls cfg80211_pmsr_wdev_down() for all interface types under
wiphy_lock.
Fix this by converting pmsr_free_wk from a plain work_struct to a
wiphy_work. The wiphy_work dispatcher holds wiphy_lock when running
work items, so the explicit guard(wiphy) in the work function is no
longer needed. wiphy_work_cancel() can be called safely while holding
wiphy_lock - since wiphy_lock prevents the work from running
concurrently, wiphy_work_cancel() never blocks, eliminating the
deadlock.
Remove the cancel_work_sync() for pmsr_free_wk from the
NETDEV_GOING_DOWN handler. cfg80211_leave(), called unconditionally
just before it, already cancels any pending work under wiphy_lock
via wiphy_work_cancel() inside cfg80211_pmsr_wdev_down(). |
| In the Linux kernel, the following vulnerability has been resolved:
mm/khugepaged: write all dirty file folios when collapsing
[There is no upstream commit, as this code was removed by upstream
commit 044925f9b565 ("mm: fs: remove filemap_nr_thps*() functions and their users")]
As-is, khugepaged and writable-file opening exclude each other. A file
cannot be open writeable and have THPs (because the filesystem is not aware
of them). khugepaged will never collapse file pages for files that are
opened writeable. On an open(O_RDWR/O_WRONLY), the page cache for that
particular file is dropped. This is fine because nothing could've been
dirtied.
However, there is an edge-case: collapse_file() might not be able to
coexist with concurrent writers, but it can coexist with dirty folios
(from previous writers). Therefore, the following can happen:
open(file, O_RDWR)
write(file)
close(file)
madvise(file_mapping, MADV_COLLAPSE, some non-dirty range)
open(file, O_RDWR)
nr_thps > 0
truncate_inode_pages()
/* THPs are cleared out, but so are the dirty folios */
When this edge-case happens, there is data loss, as the dirty folios are
fully discarded.
Fix it by fully writing back the page cache (and waiting) when collapsing
file THPs. Doing so provides the guarantee that no dirty folio will be
observed while there are active THPs. To fully ensure this is safe, the
invalidate_lock needs to be held while doing the writeout, so that
do_dentry_open()'s page cache truncation excludes this write-and-wait.
As a side effect, move the nr_thps counter bumping outside the i_pages
lock. This is correct since the counter itself is an atomic_t and the
producer <-> consumer correctness is provided by a full memory barrier:
smp_mb() in collapse_file()/memory barrier implied by full ordering in
get_write_access() -> atomic_inc_unless_negative(). |
| In the Linux kernel, the following vulnerability has been resolved:
net/iucv: take a reference on the socket found in afiucv_hs_rcv()
afiucv_hs_rcv() looks up the destination socket under iucv_sk_list.lock,
drops the lock, and then passes the socket to the afiucv_hs_callback_*()
handlers without holding a reference. AF_IUCV sockets are not
RCU-protected and are freed synchronously by iucv_sock_kill() ->
sock_put(), so a concurrent close can free the socket in the window
between read_unlock() and the handler, which then dereferences freed
memory (for example sk->sk_data_ready() in afiucv_hs_callback_syn()).
Take a reference with sock_hold() while the socket is still on the list
and release it with sock_put() once the handler has run. |
| In the Linux kernel, the following vulnerability has been resolved:
IB/mad: Drop unmatched RMPP responses before reassembly
Kernel-handled RMPP receive processing starts reassembly for active
DATA responses before the response is matched to an outstanding send.
The normal match happens later, after ib_process_rmpp_recv_wc() has
either assembled a complete message or consumed the segment.
That ordering lets an unsolicited response that routes to a kernel
RMPP agent by the high TID bits allocate or extend RMPP receive state
before the full TID and source address are checked against a real
request. A reordered burst can therefore reach the receive-side
insertion path even though the response would not match any send.
For kernel-handled RMPP DATA responses, require the existing
ib_find_send_mad() match before entering RMPP reassembly. The matcher
already checks the full TID, management class and source address/GID
against the agent wait, backlog and in-flight send lists. If there is
no match, drop the response without creating RMPP state.
This leaves the RMPP window behavior unchanged and only rejects
responses that have no corresponding request. |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: defer link RX stats percpu free to RCU
sta_remove_link() frees a removed MLO link's RX stats percpu buffer right
away, but defers only the link container to RCU:
sta_info_free_link(&alloc->info);
kfree_rcu(alloc, rcu_head);
The RX fast path reads link_sta under rcu_read_lock and writes the percpu
stats. A reader that resolved link_sta before the removal keeps the
pointer. The container stays alive from the kfree_rcu, so the read still
works. But the percpu block it points to is already freed. This needs
uses_rss. That is when pcpu_rx_stats exists.
The full STA teardown frees the deflink stats only after
synchronize_net(). The link removal path had no such barrier. The race is
hard to win in practice, but the free should still wait for RCU.
Free the link together with its data from a single RCU callback, so the
percpu block is reclaimed only after readers drain. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/xe/vf: Fix VF CCS attach/detach race with in-flight BO moves
xe_bo_move() attaches VF CCS read/write batch buffers (BBs) to a BO
after it transitions NULL/SYSTEM -> TT, and detaches them after it
transitions TT -> SYSTEM. Both operations were done synchronously on
the CPU immediately after building the move's copy/clear fence,
without waiting for that fence to signal. This creates two races with
VF migration:
- Attach happens too late relative to the copy job it is meant to
protect. If the copy job is submitted before the CCS BBs are
attached, a VF migration event that pauses execution mid-copy can
observe partially copied CCS metadata without the attach state
needed to correctly save/restore it.
- Detach happens too early relative to the copy job that moves data
out of TT. The CCS BBs are torn down right after the copy fence is
obtained, while the actual blit may still be in flight. A VF
migration event that pauses execution mid-copy can then race the
save/restore path against the still-running blit, and the CCS BBs
it would need to make sense of the paused state have already been
removed.
Fix both races:
- Move the attach call to before the copy/clear job is submitted, so
the CCS BBs are already registered by the time the copy runs. On
attach failure, unwind and bail out of the move. xe_migrate_ccs_rw_copy()
now takes the destination resource explicitly, since bo->ttm.resource
is not updated to the new resource until after the move commits.
- Detach only after explicitly waiting for the copy fence to signal,
instead of tearing down the CCS BBs immediately after obtaining it.
While here, also fix xe_sriov_vf_ccs_attach_bo() to properly unwind and
propagate errors: the per-context loop previously never broke out on
error, silently discarding earlier failures. Unwind by clearing each
attached context directly via xe_migrate_ccs_rw_copy_clear() instead of
reusing xe_sriov_vf_ccs_detach_bo(), which requires both contexts to be
attached before it will clean up either one.
(cherry picked from commit d45ad0aa7a1eb5d7288b5ed948b05695611dc39e) |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: core: wake eh reliably when using scsi_schedule_eh
Drivers which use the scsi_schedule_eh function to run the error handler
currently risk the error handler thread never waking once all commands are
timed out or inactive. There is no enforced memory order between setting
the host into error recovery state and counting busy commands. This can
result in a race with scsi_dec_host_busy where neither CPU sees both
conditions of all commands inactive and the host error state to request
waking the error handler.
To fix this, run the scsi_schedule_eh's scsi_eh_wakeup from a new work item
which will use rcu to ensure scsi_schedule_eh's call to scsi_host_busy will
occur after the error state is globally visible and will be seen by any
current scsi_dec_host_busy callers. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Fix ISM dc_lock deadlock during suspend
[Why]
System hang observed during suspend/resume while video is playing.
amdgpu_dm_ism_disable() is called under dc_lock and waits for ISM
delayed work via disable_delayed_work_sync(). The work handlers
themselves take dc_lock, producing an ABBA deadlock when a worker is
in flight at suspend time.
[How]
Split the disable path into two phases with opposite locking
contracts:
1. amdgpu_dm_ism_disable() -- quiesces workers, must NOT hold
dc_lock.
2. amdgpu_dm_ism_force_full_power() (new) -- drives the ISM FSM
back to FULL_POWER_RUNNING, must hold dc_lock. |
| In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_tcm: synchronize delayed set_alt with teardown
The f_tcm set_alt() path defers endpoint setup to a work item and
completes the delayed status response from process context. The delayed
work uses f_tcm private state and may complete the setup request after
disconnect or function teardown has already moved on.
Cancel and drain the delayed set_alt work when the function is unbound or
freed. For disable paths, which are reached under the composite device
lock, use a small state machine and a non-sleeping cancellation path
instead of cancel_work_sync(). If the work is already running, mark it
cancelled and let the worker own the cleanup; otherwise tcm_disable() can
cancel the queued work and clean up immediately.
Also serialize the final delayed-status completion with the cancellation
check while holding the composite device lock. This prevents a disconnect
from clearing delayed_status while the worker is about to complete the
control request.
Validation reproduced this kernel report:
BUG: KASAN: slab-use-after-free in tcm_delayed_set_alt+0x6c/0xef0
Call Trace:
<TASK>
dump_stack_lvl+0x66/0xa0
print_report+0xce/0x630
? tcm_delayed_set_alt+0x6c/0xef0
? srso_alias_return_thunk+0x5/0xfbef5
? __virt_addr_valid+0x188/0x320
? tcm_delayed_set_alt+0x6c/0xef0
kasan_report+0xe0/0x110
? tcm_delayed_set_alt+0x6c/0xef0
tcm_delayed_set_alt+0x6c/0xef0
? __pfx_tcm_delayed_set_alt+0x10/0x10
? process_one_work+0x4cb/0xb90
? rcu_is_watching+0x20/0x50
? tcm_delayed_set_alt+0x9/0xef0
process_one_work+0x4d7/0xb90
? __pfx_process_one_work+0x10/0x10
? srso_alias_return_thunk+0x5/0xfbef5
? __list_add_valid_or_report+0x37/0xf0
? __pfx_tcm_delayed_set_alt+0x10/0x10
? srso_alias_return_thunk+0x5/0xfbef5
worker_thread+0x2d8/0x570
? __pfx_worker_thread+0x10/0x10
kthread+0x1ad/0x1f0
? __pfx_kthread+0x10/0x10
ret_from_fork+0x3c9/0x540
? __pfx_ret_from_fork+0x10/0x10
? srso_alias_return_thunk+0x5/0xfbef5
? __switch_to+0x2e9/0x730
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
Allocated by task 544:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
__kasan_kmalloc+0x8f/0xa0
tcm_alloc+0x68/0x180
usb_get_function+0x36/0x60
config_usb_cfg_link+0x125/0x1b0
configfs_symlink+0x322/0x890
vfs_symlink+0xc2/0x270
filename_symlinkat+0x295/0x2f0
__x64_sys_symlinkat+0x62/0x90
do_syscall_64+0x115/0x6a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 661:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x43/0x70
kfree+0x2f9/0x530
config_usb_cfg_unlink+0x173/0x1e0
configfs_unlink+0x1fa/0x340
vfs_unlink+0x15c/0x510
filename_unlinkat+0x2ba/0x450
__x64_sys_unlinkat+0x63/0x90
do_syscall_64+0x115/0x6a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f |
| In the Linux kernel, the following vulnerability has been resolved:
can: raw: add locking for raw flags bitfield
With commit 890e5198a6e5 ("can: raw: use bitfields to store flags in
struct raw_sock") the formerly separate integer values have been integrated
into a single bitfield. This led to a read-modify-write operation when
changing a flag in raw_setsockopt() which now needs a locking to prevent
concurrent access.
Instead of adding a lock/unlock hell in each of the flag manipulations this
patch introduces a wrapper for a new raw_setsockopt_locked() function
analogue to the isotp_setsockopt[_locked]() approach in net/can/isotp.c
[mkl: use Closes tag instead of Link] |
| In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_sync: hold hdev->lock for hci_conn_params lookups
hci_conn_params_lookup requires hdev->lock be held, otherwise the list
iteration or param access is not safe.
Hold hdev->lock for params lookups in hci_sync. |
| In the Linux kernel, the following vulnerability has been resolved:
pds_core: fix auxiliary device add/del races
Two paths add or delete the same slot (pf->vfs[vf_id].padev): a VF's
pdsc_reset_done() and the PF's devlink enable_vnet/disable_vnet handler.
They serialize on config_lock, but neither guards the slot under it
correctly.
add() registers and stores a new auxiliary device without first checking
the slot, so a second add of an already-populated slot leaks the first
device. del() makes that check outside config_lock, so two concurrent
dels can both pass it; the first clears the slot, and the second
dereferences a NULL pointer.
Check and update the slot under config_lock in both paths. |
| In the Linux kernel, the following vulnerability has been resolved:
ksmbd: pin conn during async oplock break notification
smb2_oplock_break_noti() and smb2_lease_break_noti() store a ksmbd_conn
pointer in an async ksmbd_work and then queue that work on ksmbd-io. The
work only increments conn->r_count, which prevents teardown from passing
the pending-request wait after the increment, but it does not pin the
struct ksmbd_conn object.
If connection teardown races with an oplock break notification, the last
conn reference can be dropped before the queued worker finishes. The
worker then uses the freed conn in ksmbd_conn_write() and
ksmbd_conn_r_count_dec().
Take a real conn reference when publishing the conn pointer to the async
work item, and drop it after the notification work has decremented
r_count. Apply the same lifetime rule to lease break notification, which
uses the same work->conn pattern. |
| In the Linux kernel, the following vulnerability has been resolved:
hwmon: (nzxt-kraken3) Stop device IO before calling hid_hw_stop
Calling hid_hw_stop() does not stop the device IO.
This results in a race condition between hid_input_report() and the point
immediately following the execution of hid_device_io_start() within
the driver probe function. If the probe operation fails after "io start"
has been initiated, this race condition will result in a UAF vulnerability.
Fix the problem by calling hid_device_io_stop() before calling
hid_hw_stop(). |
| In the Linux kernel, the following vulnerability has been resolved:
net/packet: avoid fanout hook re-registration after unregister
packet_set_ring() temporarily detaches a socket from packet delivery while
reconfiguring its ring. It records the previous running state, clears
po->num, unregisters the protocol hook when needed, drops po->bind_lock,
and later restores po->num and re-registers the hook from the saved
was_running value.
That unlocked window can race with NETDEV_UNREGISTER. The notifier can
observe the socket as not running, skip __unregister_prot_hook(), and
invalidate the per-socket binding by setting po->ifindex to -1 and clearing
po->prot_hook.dev. A one-member fanout group can still retain its shared
fanout hook device pointer. When packet_set_ring() resumes, re-registering
solely from the stale was_running state can re-add the fanout hook after
the device has been unregistered.
Treat po->ifindex == -1 as an invalidated binding after reacquiring
po->bind_lock. This is distinct from ifindex 0, the normal
unbound/wildcard state: ifindex -1 marks an existing device binding that
was invalidated when the device was unregistered. Restore po->num as
before, but do not re-register the hook if device unregister already
detached the socket. |
| In the Linux kernel, the following vulnerability has been resolved:
iommu/amd: Wait for completion instead of returning early in iommu_completion_wait()
need_sync is a per-IOMMU flag shared by all domains and devices behind
that IOMMU. It is set whenever a command is queued with sync == true and
cleared when a completion-wait (CWAIT) command is queued. However, a
cleared need_sync only means that a covering CWAIT has been queued, not
that all previously queued commands have actually completed in hardware.
iommu_completion_wait() read need_sync locklessly and returned early
when it was false. This breaks the "block until all previously queued
commands have completed" contract in a multi-CPU scenario:
CPU2: queue inv-B => need_sync = true
CPU1: queue CWAIT(N); need_sync = false; then wait_on_sem(N)
CPU2: read need_sync == false => return 0 (no wait!)
CPU2 returns without waiting for any sequence number even though its
inv-B may not have completed yet (CWAIT(N), queued after inv-B, has not
been signaled). CPU2 then proceeds to, for example, free page-table
pages while the IOMMU can still walk stale translations, opening a
use-after-free window. This is a logical race in the meaning of the
flag, not a memory-visibility issue, so barriers alone do not help.
Fix it without losing the optimization of avoiding redundant CWAIT
commands: take iommu->lock before testing need_sync, and when it is
false do not return early but wait for the last allocated sequence
number (cmd_sem_val). Since need_sync == false implies no sync command
was queued after the last CWAIT, that CWAIT is FIFO-ordered after every
not-yet-completed command, so waiting for its sequence number guarantees
all prior commands (possibly queued by another CPU) have completed. The
common path with pending work is unchanged and no extra hardware command
is issued. |
