| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
nvmet-tcp: fix race between ICReq handling and queue teardown
nvmet_tcp_handle_icreq() updates queue->state after sending an
Initialization Connection Response (ICResp), but it does so without
serializing against target-side queue teardown.
If an NVMe/TCP host sends an Initialization Connection Request
(ICReq) and immediately closes the connection, target-side teardown
may start in softirq context before io_work drains the already
buffered ICReq. In that case, nvmet_tcp_schedule_release_queue()
sets queue->state to NVMET_TCP_Q_DISCONNECTING and drops the queue
reference under state_lock.
If io_work later processes that ICReq, nvmet_tcp_handle_icreq() can
still overwrite the state back to NVMET_TCP_Q_LIVE. That defeats the
DISCONNECTING-state guard in nvmet_tcp_schedule_release_queue() and
allows a later socket state change to re-enter teardown and issue a
second kref_put() on an already released queue.
The ICResp send failure path has the same problem. If teardown has
already moved the queue to DISCONNECTING, a send error can still
overwrite the state with NVMET_TCP_Q_FAILED, again reopening the
window for a second teardown path to drop the queue reference.
Fix this by serializing both post-send state transitions with
state_lock and bailing out if teardown has already started.
Use -ESHUTDOWN as an internal sentinel for that bail-out path rather
than propagating it as a transport error like -ECONNRESET. Keep
nvmet_tcp_socket_error() setting rcv_state to NVMET_TCP_RECV_ERR before
honoring that sentinel so receive-side parsing stays quiesced until the
existing release path completes. |
| In the Linux kernel, the following vulnerability has been resolved:
iommu/vt-d: Fix race condition during PASID entry replacement
The Intel VT-d PASID table entry is 512 bits (64 bytes). When replacing
an active PASID entry (e.g., during domain replacement), the current
implementation calculates a new entry on the stack and copies it to the
table using a single structure assignment.
struct pasid_entry *pte, new_pte;
pte = intel_pasid_get_entry(dev, pasid);
pasid_pte_config_first_level(iommu, &new_pte, ...);
*pte = new_pte;
Because the hardware may fetch the 512-bit PASID entry in multiple
128-bit chunks, updating the entire entry while it is active (Present
bit set) risks a "torn" read. In this scenario, the IOMMU hardware
could observe an inconsistent state — partially new data and partially
old data — leading to unpredictable behavior or spurious faults.
Fix this by removing the unsafe "replace" helpers and following the
"clear-then-update" flow, which ensures the Present bit is cleared and
the required invalidation handshake is completed before the new
configuration is applied. |
| In the Linux kernel, the following vulnerability has been resolved:
RDMA/rxe: Fix race condition in QP timer handlers
I encontered the following warning:
WARNING: drivers/infiniband/sw/rxe/rxe_task.c:249 at rxe_sched_task+0x1c8/0x238 [rdma_rxe], CPU#0: swapper/0/0
...
libsha1 [last unloaded: ip6_udp_tunnel]
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G C 6.19.0-rc5-64k-v8+ #37 PREEMPT
Tainted: [C]=CRAP
Hardware name: Raspberry Pi 4 Model B Rev 1.2
Call trace:
rxe_sched_task+0x1c8/0x238 [rdma_rxe] (P)
retransmit_timer+0x130/0x188 [rdma_rxe]
call_timer_fn+0x68/0x4d0
__run_timers+0x630/0x888
...
WARNING: drivers/infiniband/sw/rxe/rxe_task.c:38 at rxe_sched_task+0x1c0/0x238 [rdma_rxe], CPU#0: swapper/0/0
...
WARNING: drivers/infiniband/sw/rxe/rxe_task.c:111 at do_work+0x488/0x5c8 [rdma_rxe], CPU#3: kworker/u17:4/93400
...
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0x138/0x1a0, CPU#3: kworker/u17:4/93400
The issue is caused by a race condition between retransmit_timer() and
rxe_destroy_qp, leading to the Queue Pair's (QP) reference count dropping
to zero during timer handler execution.
It seems this warning is harmless because rxe_qp_do_cleanup() will flush
all pending timers and requests.
Example of flow causing the issue:
CPU0 CPU1
retransmit_timer() {
spin_lock_irqsave
rxe_destroy_qp()
__rxe_cleanup()
__rxe_put() // qp->ref_count decrease to 0
rxe_qp_do_cleanup() {
if (qp->valid) {
rxe_sched_task() {
WARN_ON(rxe_read(task->qp) <= 0);
}
}
spin_unlock_irqrestore
}
spin_lock_irqsave
qp->valid = 0
spin_unlock_irqrestore
}
Ensure the QP's reference count is maintained and its validity is checked
within the timer callbacks by adding calls to rxe_get(qp) and corresponding
rxe_put(qp) after use. |
| In the Linux kernel, the following vulnerability has been resolved:
tcp: fix potential race in tcp_v6_syn_recv_sock()
Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock()
is done too late.
After tcp_v4_syn_recv_sock(), the child socket is already visible
from TCP ehash table and other cpus might use it.
Since newinet->pinet6 is still pointing to the listener ipv6_pinfo
bad things can happen as syzbot found.
Move the problematic code in tcp_v6_mapped_child_init()
and call this new helper from tcp_v4_syn_recv_sock() before
the ehash insertion.
This allows the removal of one tcp_sync_mss(), since
tcp_v4_syn_recv_sock() will call it with the correct
context. |
| In the Linux kernel, the following vulnerability has been resolved:
netfilter: ctnetlink: ensure safe access to master conntrack
Holding reference on the expectation is not sufficient, the master
conntrack object can just go away, making exp->master invalid.
To access exp->master safely:
- Grab the nf_conntrack_expect_lock, this gets serialized with
clean_from_lists() which also holds this lock when the master
conntrack goes away.
- Hold reference on master conntrack via nf_conntrack_find_get().
Not so easy since the master tuple to look up for the master conntrack
is not available in the existing problematic paths.
This patch goes for extending the nf_conntrack_expect_lock section
to address this issue for simplicity, in the cases that are described
below this is just slightly extending the lock section.
The add expectation command already holds a reference to the master
conntrack from ctnetlink_create_expect().
However, the delete expectation command needs to grab the spinlock
before looking up for the expectation. Expand the existing spinlock
section to address this to cover the expectation lookup. Note that,
the nf_ct_expect_iterate_net() calls already grabs the spinlock while
iterating over the expectation table, which is correct.
The get expectation command needs to grab the spinlock to ensure master
conntrack does not go away. This also expands the existing spinlock
section to cover the expectation lookup too. I needed to move the
netlink skb allocation out of the spinlock to keep it GFP_KERNEL.
For the expectation events, the IPEXP_DESTROY event is already delivered
under the spinlock, just move the delivery of IPEXP_NEW under the
spinlock too because the master conntrack event cache is reached through
exp->master.
While at it, add lockdep notations to help identify what codepaths need
to grab the spinlock. |
| In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: SCO: fix race conditions in sco_sock_connect()
sco_sock_connect() checks sk_state and sk_type without holding
the socket lock. Two concurrent connect() syscalls on the same
socket can both pass the check and enter sco_connect(), leading
to use-after-free.
The buggy scenario involves three participants and was confirmed
with additional logging instrumentation:
Thread A (connect): HCI disconnect: Thread B (connect):
sco_sock_connect(sk) sco_sock_connect(sk)
sk_state==BT_OPEN sk_state==BT_OPEN
(pass, no lock) (pass, no lock)
sco_connect(sk): sco_connect(sk):
hci_dev_lock hci_dev_lock
hci_connect_sco <- blocked
-> hcon1
sco_conn_add->conn1
lock_sock(sk)
sco_chan_add:
conn1->sk = sk
sk->conn = conn1
sk_state=BT_CONNECT
release_sock
hci_dev_unlock
hci_dev_lock
sco_conn_del:
lock_sock(sk)
sco_chan_del:
sk->conn=NULL
conn1->sk=NULL
sk_state=
BT_CLOSED
SOCK_ZAPPED
release_sock
hci_dev_unlock
(unblocked)
hci_connect_sco
-> hcon2
sco_conn_add
-> conn2
lock_sock(sk)
sco_chan_add:
sk->conn=conn2
sk_state=
BT_CONNECT
// zombie sk!
release_sock
hci_dev_unlock
Thread B revives a BT_CLOSED + SOCK_ZAPPED socket back to
BT_CONNECT. Subsequent cleanup triggers double sock_put() and
use-after-free. Meanwhile conn1 is leaked as it was orphaned
when sco_conn_del() cleared the association.
Fix this by:
- Moving lock_sock() before the sk_state/sk_type checks in
sco_sock_connect() to serialize concurrent connect attempts
- Fixing the sk_type != SOCK_SEQPACKET check to actually
return the error instead of just assigning it
- Adding a state re-check in sco_connect() after lock_sock()
to catch state changes during the window between the locks
- Adding sco_pi(sk)->conn check in sco_chan_add() to prevent
double-attach of a socket to multiple connections
- Adding hci_conn_drop() on sco_chan_add failure to prevent
HCI connection leaks |
| In the Linux kernel, the following vulnerability has been resolved:
net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()
In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points
directly into the mmap'd TX ring buffer shared with userspace. The
kernel validates the header via __packet_snd_vnet_parse() but then
re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent
userspace thread can modify the vnet_hdr fields between validation
and use, bypassing all safety checks.
The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr
to a stack-local variable. All other vnet_hdr consumers in the kernel
(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX
path is the only caller of virtio_net_hdr_to_skb() that reads directly
from user-controlled shared memory.
Fix this by copying vnet_hdr from the mmap'd ring buffer to a
stack-local variable before validation and use, consistent with the
approach used in packet_snd() and all other callers. |
| In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: Fix race condition during IPSec ESN update
In IPSec full offload mode, the device reports an ESN (Extended
Sequence Number) wrap event to the driver. The driver validates this
event by querying the IPSec ASO and checking that the esn_event_arm
field is 0x0, which indicates an event has occurred. After handling
the event, the driver must re-arm the context by setting esn_event_arm
back to 0x1.
A race condition exists in this handling path. After validating the
event, the driver calls mlx5_accel_esp_modify_xfrm() to update the
kernel's xfrm state. This function temporarily releases and
re-acquires the xfrm state lock.
So, need to acknowledge the event first by setting esn_event_arm to
0x1. This prevents the driver from reprocessing the same ESN update if
the hardware sends events for other reason. Since the next ESN update
only occurs after nearly 2^31 packets are received, there's no risk of
missing an update, as it will happen long after this handling has
finished.
Processing the event twice causes the ESN high-order bits (esn_msb) to
be incremented incorrectly. The driver then programs the hardware with
this invalid ESN state, which leads to anti-replay failures and a
complete halt of IPSec traffic.
Fix this by re-arming the ESN event immediately after it is validated,
before calling mlx5_accel_esp_modify_xfrm(). This ensures that any
spurious, duplicate events are correctly ignored, closing the race
window. |
| In the Linux kernel, the following vulnerability has been resolved:
perf: Fix __perf_event_overflow() vs perf_remove_from_context() race
Make sure that __perf_event_overflow() runs with IRQs disabled for all
possible callchains. Specifically the software events can end up running
it with only preemption disabled.
This opens up a race vs perf_event_exit_event() and friends that will go
and free various things the overflow path expects to be present, like
the BPF program. |
| In the Linux kernel, the following vulnerability has been resolved:
tls: Fix race condition in tls_sw_cancel_work_tx()
This issue was discovered during a code audit.
After cancel_delayed_work_sync() is called from tls_sk_proto_close(),
tx_work_handler() can still be scheduled from paths such as the
Delayed ACK handler or ksoftirqd.
As a result, the tx_work_handler() worker may dereference a freed
TLS object.
The following is a simple race scenario:
cpu0 cpu1
tls_sk_proto_close()
tls_sw_cancel_work_tx()
tls_write_space()
tls_sw_write_space()
if (!test_and_set_bit(BIT_TX_SCHEDULED, &tx_ctx->tx_bitmask))
set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask);
cancel_delayed_work_sync(&ctx->tx_work.work);
schedule_delayed_work(&tx_ctx->tx_work.work, 0);
To prevent this race condition, cancel_delayed_work_sync() is
replaced with disable_delayed_work_sync(). |
| In the Linux kernel, the following vulnerability has been resolved:
espintcp: Fix race condition in espintcp_close()
This issue was discovered during a code audit.
After cancel_work_sync() is called from espintcp_close(),
espintcp_tx_work() can still be scheduled from paths such as
the Delayed ACK handler or ksoftirqd.
As a result, the espintcp_tx_work() worker may dereference a
freed espintcp ctx or sk.
The following is a simple race scenario:
cpu0 cpu1
espintcp_close()
cancel_work_sync(&ctx->work);
espintcp_write_space()
schedule_work(&ctx->work);
To prevent this race condition, cancel_work_sync() is
replaced with disable_work_sync(). |
| In the Linux kernel, the following vulnerability has been resolved:
smb: client: split cached_fid bitfields to avoid shared-byte RMW races
is_open, has_lease and on_list are stored in the same bitfield byte in
struct cached_fid but are updated in different code paths that may run
concurrently. Bitfield assignments generate byte read–modify–write
operations (e.g. `orb $mask, addr` on x86_64), so updating one flag can
restore stale values of the others.
A possible interleaving is:
CPU1: load old byte (has_lease=1, on_list=1)
CPU2: clear both flags (store 0)
CPU1: RMW store (old | IS_OPEN) -> reintroduces cleared bits
To avoid this class of races, convert these flags to separate bool
fields. |
| In the Linux kernel, the following vulnerability has been resolved:
rpmsg: core: fix race in driver_override_show() and use core helper
The driver_override_show function reads the driver_override string
without holding the device_lock. However, the store function modifies
and frees the string while holding the device_lock. This creates a race
condition where the string can be freed by the store function while
being read by the show function, leading to a use-after-free.
To fix this, replace the rpmsg_string_attr macro with explicit show and
store functions. The new driver_override_store uses the standard
driver_set_override helper. Since the introduction of
driver_set_override, the comments in include/linux/rpmsg.h have stated
that this helper must be used to set or clear driver_override, but the
implementation was not updated until now.
Because driver_set_override modifies and frees the string while holding
the device_lock, the new driver_override_show now correctly holds the
device_lock during the read operation to prevent the race.
Additionally, since rpmsg_string_attr has only ever been used for
driver_override, removing the macro simplifies the code. |
| Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Autopilot allows an authorized attacker to elevate privileges locally. |
| Concurrent execution using shared resource with improper synchronization ('race condition') in ASP.NET Core allows an authorized attacker to elevate privileges over a network. |
| In the Linux kernel, the following vulnerability has been resolved:
ppp: fix race conditions in ppp_fill_forward_path
ppp_fill_forward_path() has two race conditions:
1. The ppp->channels list can change between list_empty() and
list_first_entry(), as ppp_lock() is not held. If the only channel
is deleted in ppp_disconnect_channel(), list_first_entry() may
access an empty head or a freed entry, and trigger a panic.
2. pch->chan can be NULL. When ppp_unregister_channel() is called,
pch->chan is set to NULL before pch is removed from ppp->channels.
Fix these by using a lockless RCU approach:
- Use list_first_or_null_rcu() to safely test and access the first list
entry.
- Convert list modifications on ppp->channels to their RCU variants and
add synchronize_net() after removal.
- Check for a NULL pch->chan before dereferencing it. |
| In the Linux kernel, the following vulnerability has been resolved:
xsk: Fix race condition in AF_XDP generic RX path
Move rx_lock from xsk_socket to xsk_buff_pool.
Fix synchronization for shared umem mode in
generic RX path where multiple sockets share
single xsk_buff_pool.
RX queue is exclusive to xsk_socket, while FILL
queue can be shared between multiple sockets.
This could result in race condition where two
CPU cores access RX path of two different sockets
sharing the same umem.
Protect both queues by acquiring spinlock in shared
xsk_buff_pool.
Lock contention may be minimized in the future by some
per-thread FQ buffering.
It's safe and necessary to move spin_lock_bh(rx_lock)
after xsk_rcv_check():
* xs->pool and spinlock_init is synchronized by
xsk_bind() -> xsk_is_bound() memory barriers.
* xsk_rcv_check() may return true at the moment
of xsk_release() or xsk_unbind_dev(),
however this will not cause any data races or
race conditions. xsk_unbind_dev() removes xdp
socket from all maps and waits for completion
of all outstanding rx operations. Packets in
RX path will either complete safely or drop. |
| In the Linux kernel, the following vulnerability has been resolved:
bpf, sockmap: Fix race between element replace and close()
Element replace (with a socket different from the one stored) may race
with socket's close() link popping & unlinking. __sock_map_delete()
unconditionally unrefs the (wrong) element:
// set map[0] = s0
map_update_elem(map, 0, s0)
// drop fd of s0
close(s0)
sock_map_close()
lock_sock(sk) (s0!)
sock_map_remove_links(sk)
link = sk_psock_link_pop()
sock_map_unlink(sk, link)
sock_map_delete_from_link
// replace map[0] with s1
map_update_elem(map, 0, s1)
sock_map_update_elem
(s1!) lock_sock(sk)
sock_map_update_common
psock = sk_psock(sk)
spin_lock(&stab->lock)
osk = stab->sks[idx]
sock_map_add_link(..., &stab->sks[idx])
sock_map_unref(osk, &stab->sks[idx])
psock = sk_psock(osk)
sk_psock_put(sk, psock)
if (refcount_dec_and_test(&psock))
sk_psock_drop(sk, psock)
spin_unlock(&stab->lock)
unlock_sock(sk)
__sock_map_delete
spin_lock(&stab->lock)
sk = *psk // s1 replaced s0; sk == s1
if (!sk_test || sk_test == sk) // sk_test (s0) != sk (s1); no branch
sk = xchg(psk, NULL)
if (sk)
sock_map_unref(sk, psk) // unref s1; sks[idx] will dangle
psock = sk_psock(sk)
sk_psock_put(sk, psock)
if (refcount_dec_and_test())
sk_psock_drop(sk, psock)
spin_unlock(&stab->lock)
release_sock(sk)
Then close(map) enqueues bpf_map_free_deferred, which finally calls
sock_map_free(). This results in some refcount_t warnings along with
a KASAN splat [1].
Fix __sock_map_delete(), do not allow sock_map_unref() on elements that
may have been replaced.
[1]:
BUG: KASAN: slab-use-after-free in sock_map_free+0x10e/0x330
Write of size 4 at addr ffff88811f5b9100 by task kworker/u64:12/1063
CPU: 14 UID: 0 PID: 1063 Comm: kworker/u64:12 Not tainted 6.12.0+ #125
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
Workqueue: events_unbound bpf_map_free_deferred
Call Trace:
<TASK>
dump_stack_lvl+0x68/0x90
print_report+0x174/0x4f6
kasan_report+0xb9/0x190
kasan_check_range+0x10f/0x1e0
sock_map_free+0x10e/0x330
bpf_map_free_deferred+0x173/0x320
process_one_work+0x846/0x1420
worker_thread+0x5b3/0xf80
kthread+0x29e/0x360
ret_from_fork+0x2d/0x70
ret_from_fork_asm+0x1a/0x30
</TASK>
Allocated by task 1202:
kasan_save_stack+0x1e/0x40
kasan_save_track+0x10/0x30
__kasan_slab_alloc+0x85/0x90
kmem_cache_alloc_noprof+0x131/0x450
sk_prot_alloc+0x5b/0x220
sk_alloc+0x2c/0x870
unix_create1+0x88/0x8a0
unix_create+0xc5/0x180
__sock_create+0x241/0x650
__sys_socketpair+0x1ce/0x420
__x64_sys_socketpair+0x92/0x100
do_syscall_64+0x93/0x180
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Freed by task 46:
kasan_save_stack+0x1e/0x40
kasan_save_track+0x10/0x30
kasan_save_free_info+0x37/0x60
__kasan_slab_free+0x4b/0x70
kmem_cache_free+0x1a1/0x590
__sk_destruct+0x388/0x5a0
sk_psock_destroy+0x73e/0xa50
process_one_work+0x846/0x1420
worker_thread+0x5b3/0xf80
kthread+0x29e/0x360
ret_from_fork+0x2d/0x70
ret_from_fork_asm+0x1a/0x30
The bu
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
netfilter: ipset: Hold module reference while requesting a module
User space may unload ip_set.ko while it is itself requesting a set type
backend module, leading to a kernel crash. The race condition may be
provoked by inserting an mdelay() right after the nfnl_unlock() call. |
| In the Linux kernel, the following vulnerability has been resolved:
blk-rq-qos: fix crash on rq_qos_wait vs. rq_qos_wake_function race
We're seeing crashes from rq_qos_wake_function that look like this:
BUG: unable to handle page fault for address: ffffafe180a40084
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 100000067 P4D 100000067 PUD 10027c067 PMD 10115d067 PTE 0
Oops: Oops: 0002 [#1] PREEMPT SMP PTI
CPU: 17 UID: 0 PID: 0 Comm: swapper/17 Not tainted 6.12.0-rc3-00013-geca631b8fe80 #11
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
RIP: 0010:_raw_spin_lock_irqsave+0x1d/0x40
Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 41 54 9c 41 5c fa 65 ff 05 62 97 30 4c 31 c0 ba 01 00 00 00 <f0> 0f b1 17 75 0a 4c 89 e0 41 5c c3 cc cc cc cc 89 c6 e8 2c 0b 00
RSP: 0018:ffffafe180580ca0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffffafe180a3f7a8 RCX: 0000000000000011
RDX: 0000000000000001 RSI: 0000000000000003 RDI: ffffafe180a40084
RBP: 0000000000000000 R08: 00000000001e7240 R09: 0000000000000011
R10: 0000000000000028 R11: 0000000000000888 R12: 0000000000000002
R13: ffffafe180a40084 R14: 0000000000000000 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff9aaf1f280000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffafe180a40084 CR3: 000000010e428002 CR4: 0000000000770ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<IRQ>
try_to_wake_up+0x5a/0x6a0
rq_qos_wake_function+0x71/0x80
__wake_up_common+0x75/0xa0
__wake_up+0x36/0x60
scale_up.part.0+0x50/0x110
wb_timer_fn+0x227/0x450
...
So rq_qos_wake_function() calls wake_up_process(data->task), which calls
try_to_wake_up(), which faults in raw_spin_lock_irqsave(&p->pi_lock).
p comes from data->task, and data comes from the waitqueue entry, which
is stored on the waiter's stack in rq_qos_wait(). Analyzing the core
dump with drgn, I found that the waiter had already woken up and moved
on to a completely unrelated code path, clobbering what was previously
data->task. Meanwhile, the waker was passing the clobbered garbage in
data->task to wake_up_process(), leading to the crash.
What's happening is that in between rq_qos_wake_function() deleting the
waitqueue entry and calling wake_up_process(), rq_qos_wait() is finding
that it already got a token and returning. The race looks like this:
rq_qos_wait() rq_qos_wake_function()
==============================================================
prepare_to_wait_exclusive()
data->got_token = true;
list_del_init(&curr->entry);
if (data.got_token)
break;
finish_wait(&rqw->wait, &data.wq);
^- returns immediately because
list_empty_careful(&wq_entry->entry)
is true
... return, go do something else ...
wake_up_process(data->task)
(NO LONGER VALID!)-^
Normally, finish_wait() is supposed to synchronize against the waker.
But, as noted above, it is returning immediately because the waitqueue
entry has already been removed from the waitqueue.
The bug is that rq_qos_wake_function() is accessing the waitqueue entry
AFTER deleting it. Note that autoremove_wake_function() wakes the waiter
and THEN deletes the waitqueue entry, which is the proper order.
Fix it by swapping the order. We also need to use
list_del_init_careful() to match the list_empty_careful() in
finish_wait(). |
