| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
net: rds: don't hold sock lock when cancelling work from rds_tcp_reset_callbacks()
syzbot is reporting lockdep warning at rds_tcp_reset_callbacks() [1], for
commit ac3615e7f3cffe2a ("RDS: TCP: Reduce code duplication in
rds_tcp_reset_callbacks()") added cancel_delayed_work_sync() into a section
protected by lock_sock() without realizing that rds_send_xmit() might call
lock_sock().
We don't need to protect cancel_delayed_work_sync() using lock_sock(), for
even if rds_{send,recv}_worker() re-queued this work while __flush_work()
from cancel_delayed_work_sync() was waiting for this work to complete,
retried rds_{send,recv}_worker() is no-op due to the absence of RDS_CONN_UP
bit. |
| In the Linux kernel, the following vulnerability has been resolved:
riscv: vdso: fix NULL deference in vdso_join_timens() when vfork
Testing tools/testing/selftests/timens/vfork_exec.c got below
kernel log:
[ 6.838454] Unable to handle kernel access to user memory without uaccess routines at virtual address 0000000000000020
[ 6.842255] Oops [#1]
[ 6.842871] Modules linked in:
[ 6.844249] CPU: 1 PID: 64 Comm: vfork_exec Not tainted 6.0.0-rc3-rt15+ #8
[ 6.845861] Hardware name: riscv-virtio,qemu (DT)
[ 6.848009] epc : vdso_join_timens+0xd2/0x110
[ 6.850097] ra : vdso_join_timens+0xd2/0x110
[ 6.851164] epc : ffffffff8000635c ra : ffffffff8000635c sp : ff6000000181fbf0
[ 6.852562] gp : ffffffff80cff648 tp : ff60000000fdb700 t0 : 3030303030303030
[ 6.853852] t1 : 0000000000000030 t2 : 3030303030303030 s0 : ff6000000181fc40
[ 6.854984] s1 : ff60000001e6c000 a0 : 0000000000000010 a1 : ffffffff8005654c
[ 6.856221] a2 : 00000000ffffefff a3 : 0000000000000000 a4 : 0000000000000000
[ 6.858114] a5 : 0000000000000000 a6 : 0000000000000008 a7 : 0000000000000038
[ 6.859484] s2 : ff60000001e6c068 s3 : ff6000000108abb0 s4 : 0000000000000000
[ 6.860751] s5 : 0000000000001000 s6 : ffffffff8089dc40 s7 : ffffffff8089dc38
[ 6.862029] s8 : ffffffff8089dc30 s9 : ff60000000fdbe38 s10: 000000000000005e
[ 6.863304] s11: ffffffff80cc3510 t3 : ffffffff80d1112f t4 : ffffffff80d1112f
[ 6.864565] t5 : ffffffff80d11130 t6 : ff6000000181fa00
[ 6.865561] status: 0000000000000120 badaddr: 0000000000000020 cause: 000000000000000d
[ 6.868046] [<ffffffff8008dc94>] timens_commit+0x38/0x11a
[ 6.869089] [<ffffffff8008dde8>] timens_on_fork+0x72/0xb4
[ 6.870055] [<ffffffff80190096>] begin_new_exec+0x3c6/0x9f0
[ 6.871231] [<ffffffff801d826c>] load_elf_binary+0x628/0x1214
[ 6.872304] [<ffffffff8018ee7a>] bprm_execve+0x1f2/0x4e4
[ 6.873243] [<ffffffff8018f90c>] do_execveat_common+0x16e/0x1ee
[ 6.874258] [<ffffffff8018f9c8>] sys_execve+0x3c/0x48
[ 6.875162] [<ffffffff80003556>] ret_from_syscall+0x0/0x2
[ 6.877484] ---[ end trace 0000000000000000 ]---
This is because the mm->context.vdso_info is NULL in vfork case. From
another side, mm->context.vdso_info either points to vdso info
for RV64 or vdso info for compat, there's no need to bloat riscv's
mm_context_t, we can handle the difference when setup the additional
page for vdso. |
| In the Linux kernel, the following vulnerability has been resolved:
mmc: omap_hsmmc: fix return value check of mmc_add_host()
mmc_add_host() may return error, if we ignore its return value,
it will lead two issues:
1. The memory that allocated in mmc_alloc_host() is leaked.
2. In the remove() path, mmc_remove_host() will be called to
delete device, but it's not added yet, it will lead a kernel
crash because of null-ptr-deref in device_del().
Fix this by checking the return value and goto error path wihch
will call mmc_free_host(). |
| In the Linux kernel, the following vulnerability has been resolved:
ext4: fix deadlock due to mbcache entry corruption
When manipulating xattr blocks, we can deadlock infinitely looping
inside ext4_xattr_block_set() where we constantly keep finding xattr
block for reuse in mbcache but we are unable to reuse it because its
reference count is too big. This happens because cache entry for the
xattr block is marked as reusable (e_reusable set) although its
reference count is too big. When this inconsistency happens, this
inconsistent state is kept indefinitely and so ext4_xattr_block_set()
keeps retrying indefinitely.
The inconsistent state is caused by non-atomic update of e_reusable bit.
e_reusable is part of a bitfield and e_reusable update can race with
update of e_referenced bit in the same bitfield resulting in loss of one
of the updates. Fix the problem by using atomic bitops instead.
This bug has been around for many years, but it became *much* easier
to hit after commit 65f8b80053a1 ("ext4: fix race when reusing xattr
blocks"). |
| In the Linux kernel, the following vulnerability has been resolved:
net: stmmac: fix possible memory leak in stmmac_dvr_probe()
The bitmap_free() should be called to free priv->af_xdp_zc_qps
when create_singlethread_workqueue() fails, otherwise there will
be a memory leak, so we add the err path error_wq_init to fix it. |
| In the Linux kernel, the following vulnerability has been resolved:
hwrng: geode - Fix PCI device refcount leak
for_each_pci_dev() is implemented by pci_get_device(). The comment of
pci_get_device() says that it will increase the reference count for the
returned pci_dev and also decrease the reference count for the input
pci_dev @from if it is not NULL.
If we break for_each_pci_dev() loop with pdev not NULL, we need to call
pci_dev_put() to decrease the reference count. We add a new struct
'amd_geode_priv' to record pointer of the pci_dev and membase, and then
add missing pci_dev_put() for the normal and error path. |
| In the Linux kernel, the following vulnerability has been resolved:
riscv: mm: add missing memcpy in kasan_init
Hi Atish,
It seems that the panic is due to the missing memcpy during kasan_init.
Could you please check whether this patch is helpful?
When doing kasan_populate, the new allocated base_pud/base_p4d should
contain kasan_early_shadow_{pud, p4d}'s content. Add the missing memcpy
to avoid page fault when read/write kasan shadow region.
Tested on:
- qemu with sv57 and CONFIG_KASAN on.
- qemu with sv48 and CONFIG_KASAN on. |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix panic due to wrong pageattr of im->image
In the scenario where livepatch and kretfunc coexist, the pageattr of
im->image is rox after arch_prepare_bpf_trampoline in
bpf_trampoline_update, and then modify_fentry or register_fentry returns
-EAGAIN from bpf_tramp_ftrace_ops_func, the BPF_TRAMP_F_ORIG_STACK flag
will be configured, and arch_prepare_bpf_trampoline will be re-executed.
At this time, because the pageattr of im->image is rox,
arch_prepare_bpf_trampoline will read and write im->image, which causes
a fault. as follows:
insmod livepatch-sample.ko # samples/livepatch/livepatch-sample.c
bpftrace -e 'kretfunc:cmdline_proc_show {}'
BUG: unable to handle page fault for address: ffffffffa0206000
PGD 322d067 P4D 322d067 PUD 322e063 PMD 1297e067 PTE d428061
Oops: 0003 [#1] PREEMPT SMP PTI
CPU: 2 PID: 270 Comm: bpftrace Tainted: G E K 6.1.0 #5
RIP: 0010:arch_prepare_bpf_trampoline+0xed/0x8c0
RSP: 0018:ffffc90001083ad8 EFLAGS: 00010202
RAX: ffffffffa0206000 RBX: 0000000000000020 RCX: 0000000000000000
RDX: ffffffffa0206001 RSI: ffffffffa0206000 RDI: 0000000000000030
RBP: ffffc90001083b70 R08: 0000000000000066 R09: ffff88800f51b400
R10: 000000002e72c6e5 R11: 00000000d0a15080 R12: ffff8880110a68c8
R13: 0000000000000000 R14: ffff88800f51b400 R15: ffffffff814fec10
FS: 00007f87bc0dc780(0000) GS:ffff88803e600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffa0206000 CR3: 0000000010b70000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bpf_trampoline_update+0x25a/0x6b0
__bpf_trampoline_link_prog+0x101/0x240
bpf_trampoline_link_prog+0x2d/0x50
bpf_tracing_prog_attach+0x24c/0x530
bpf_raw_tp_link_attach+0x73/0x1d0
__sys_bpf+0x100e/0x2570
__x64_sys_bpf+0x1c/0x30
do_syscall_64+0x5b/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
With this patch, when modify_fentry or register_fentry returns -EAGAIN
from bpf_tramp_ftrace_ops_func, the pageattr of im->image will be reset
to nx+rw. |
| In the Linux kernel, the following vulnerability has been resolved:
ftrace: Fix recursive locking direct_mutex in ftrace_modify_direct_caller
Naveen reported recursive locking of direct_mutex with sample
ftrace-direct-modify.ko:
[ 74.762406] WARNING: possible recursive locking detected
[ 74.762887] 6.0.0-rc6+ #33 Not tainted
[ 74.763216] --------------------------------------------
[ 74.763672] event-sample-fn/1084 is trying to acquire lock:
[ 74.764152] ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
register_ftrace_function+0x1f/0x180
[ 74.764922]
[ 74.764922] but task is already holding lock:
[ 74.765421] ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
modify_ftrace_direct+0x34/0x1f0
[ 74.766142]
[ 74.766142] other info that might help us debug this:
[ 74.766701] Possible unsafe locking scenario:
[ 74.766701]
[ 74.767216] CPU0
[ 74.767437] ----
[ 74.767656] lock(direct_mutex);
[ 74.767952] lock(direct_mutex);
[ 74.768245]
[ 74.768245] *** DEADLOCK ***
[ 74.768245]
[ 74.768750] May be due to missing lock nesting notation
[ 74.768750]
[ 74.769332] 1 lock held by event-sample-fn/1084:
[ 74.769731] #0: ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
modify_ftrace_direct+0x34/0x1f0
[ 74.770496]
[ 74.770496] stack backtrace:
[ 74.770884] CPU: 4 PID: 1084 Comm: event-sample-fn Not tainted ...
[ 74.771498] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), ...
[ 74.772474] Call Trace:
[ 74.772696] <TASK>
[ 74.772896] dump_stack_lvl+0x44/0x5b
[ 74.773223] __lock_acquire.cold.74+0xac/0x2b7
[ 74.773616] lock_acquire+0xd2/0x310
[ 74.773936] ? register_ftrace_function+0x1f/0x180
[ 74.774357] ? lock_is_held_type+0xd8/0x130
[ 74.774744] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.775213] __mutex_lock+0x99/0x1010
[ 74.775536] ? register_ftrace_function+0x1f/0x180
[ 74.775954] ? slab_free_freelist_hook.isra.43+0x115/0x160
[ 74.776424] ? ftrace_set_hash+0x195/0x220
[ 74.776779] ? register_ftrace_function+0x1f/0x180
[ 74.777194] ? kfree+0x3e1/0x440
[ 74.777482] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.777941] ? __schedule+0xb40/0xb40
[ 74.778258] ? register_ftrace_function+0x1f/0x180
[ 74.778672] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.779128] register_ftrace_function+0x1f/0x180
[ 74.779527] ? ftrace_set_filter_ip+0x33/0x70
[ 74.779910] ? __schedule+0xb40/0xb40
[ 74.780231] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.780678] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.781147] ftrace_modify_direct_caller+0x5b/0x90
[ 74.781563] ? 0xffffffffa0201000
[ 74.781859] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.782309] modify_ftrace_direct+0x1b2/0x1f0
[ 74.782690] ? __schedule+0xb40/0xb40
[ 74.783014] ? simple_thread+0x2a/0xb0 [ftrace_direct_modify]
[ 74.783508] ? __schedule+0xb40/0xb40
[ 74.783832] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.784294] simple_thread+0x76/0xb0 [ftrace_direct_modify]
[ 74.784766] kthread+0xf5/0x120
[ 74.785052] ? kthread_complete_and_exit+0x20/0x20
[ 74.785464] ret_from_fork+0x22/0x30
[ 74.785781] </TASK>
Fix this by using register_ftrace_function_nolock in
ftrace_modify_direct_caller. |
| In the Linux kernel, the following vulnerability has been resolved:
mmc: atmel-mci: fix return value check of mmc_add_host()
mmc_add_host() may return error, if we ignore its return value,
it will lead two issues:
1. The memory that allocated in mmc_alloc_host() is leaked.
2. In the remove() path, mmc_remove_host() will be called to
delete device, but it's not added yet, it will lead a kernel
crash because of null-ptr-deref in device_del().
So fix this by checking the return value and calling mmc_free_host()
in the error path. |
| In the Linux kernel, the following vulnerability has been resolved:
EDAC/i10nm: fix refcount leak in pci_get_dev_wrapper()
As the comment of pci_get_domain_bus_and_slot() says, it returns
a PCI device with refcount incremented, so it doesn't need to
call an extra pci_dev_get() in pci_get_dev_wrapper(), and the PCI
device needs to be put in the error path. |
| In the Linux kernel, the following vulnerability has been resolved:
clk: ti: dra7-atl: Fix reference leak in of_dra7_atl_clk_probe
pm_runtime_get_sync() will increment pm usage counter.
Forgetting to putting operation will result in reference leak.
Add missing pm_runtime_put_sync in some error paths. |
| In the Linux kernel, the following vulnerability has been resolved:
io-wq: Fix memory leak in worker creation
If the CPU mask allocation for a node fails, then the memory allocated for
the 'io_wqe' struct of the current node doesn't get freed on the error
handling path, since it has not yet been added to the 'wqes' array.
This was spotted when fuzzing v6.1-rc1 with Syzkaller:
BUG: memory leak
unreferenced object 0xffff8880093d5000 (size 1024):
comm "syz-executor.2", pid 7701, jiffies 4295048595 (age 13.900s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<00000000cb463369>] __kmem_cache_alloc_node+0x18e/0x720
[<00000000147a3f9c>] kmalloc_node_trace+0x2a/0x130
[<000000004e107011>] io_wq_create+0x7b9/0xdc0
[<00000000c38b2018>] io_uring_alloc_task_context+0x31e/0x59d
[<00000000867399da>] __io_uring_add_tctx_node.cold+0x19/0x1ba
[<000000007e0e7a79>] io_uring_setup.cold+0x1b80/0x1dce
[<00000000b545e9f6>] __x64_sys_io_uring_setup+0x5d/0x80
[<000000008a8a7508>] do_syscall_64+0x5d/0x90
[<000000004ac08bec>] entry_SYSCALL_64_after_hwframe+0x63/0xcd |
| In the Linux kernel, the following vulnerability has been resolved:
cpufreq: qcom-hw: Fix memory leak in qcom_cpufreq_hw_read_lut()
If "cpu_dev" fails to get opp table in qcom_cpufreq_hw_read_lut(),
the program will return, resulting in "table" resource is not released. |
| In the Linux kernel, the following vulnerability has been resolved:
powerpc/kprobes: Fix null pointer reference in arch_prepare_kprobe()
I found a null pointer reference in arch_prepare_kprobe():
# echo 'p cmdline_proc_show' > kprobe_events
# echo 'p cmdline_proc_show+16' >> kprobe_events
Kernel attempted to read user page (0) - exploit attempt? (uid: 0)
BUG: Kernel NULL pointer dereference on read at 0x00000000
Faulting instruction address: 0xc000000000050bfc
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV
Modules linked in:
CPU: 0 PID: 122 Comm: sh Not tainted 6.0.0-rc3-00007-gdcf8e5633e2e #10
NIP: c000000000050bfc LR: c000000000050bec CTR: 0000000000005bdc
REGS: c0000000348475b0 TRAP: 0300 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e)
MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 88002444 XER: 20040006
CFAR: c00000000022d100 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
...
NIP arch_prepare_kprobe+0x10c/0x2d0
LR arch_prepare_kprobe+0xfc/0x2d0
Call Trace:
0xc0000000012f77a0 (unreliable)
register_kprobe+0x3c0/0x7a0
__register_trace_kprobe+0x140/0x1a0
__trace_kprobe_create+0x794/0x1040
trace_probe_create+0xc4/0xe0
create_or_delete_trace_kprobe+0x2c/0x80
trace_parse_run_command+0xf0/0x210
probes_write+0x20/0x40
vfs_write+0xfc/0x450
ksys_write+0x84/0x140
system_call_exception+0x17c/0x3a0
system_call_vectored_common+0xe8/0x278
--- interrupt: 3000 at 0x7fffa5682de0
NIP: 00007fffa5682de0 LR: 0000000000000000 CTR: 0000000000000000
REGS: c000000034847e80 TRAP: 3000 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e)
MSR: 900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 44002408 XER: 00000000
The address being probed has some special:
cmdline_proc_show: Probe based on ftrace
cmdline_proc_show+16: Probe for the next instruction at the ftrace location
The ftrace-based kprobe does not generate kprobe::ainsn::insn, it gets
set to NULL. In arch_prepare_kprobe() it will check for:
...
prev = get_kprobe(p->addr - 1);
preempt_enable_no_resched();
if (prev && ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
...
If prev is based on ftrace, 'ppc_inst_read(prev->ainsn.insn)' will occur
with a null pointer reference. At this point prev->addr will not be a
prefixed instruction, so the check can be skipped.
Check if prev is ftrace-based kprobe before reading 'prev->ainsn.insn'
to fix this problem.
[mpe: Trim oops] |
| In the Linux kernel, the following vulnerability has been resolved:
drivers: perf: marvell_cn10k: Fix hotplug callback leak in tad_pmu_init()
tad_pmu_init() won't remove the callback added by cpuhp_setup_state_multi()
when platform_driver_register() failed. Remove the callback by
cpuhp_remove_multi_state() in fail path.
Similar to the handling of arm_ccn_init() in commit 26242b330093 ("bus:
arm-ccn: Prevent hotplug callback leak") |
| In the Linux kernel, the following vulnerability has been resolved:
HSI: omap_ssi: Fix refcount leak in ssi_probe
When returning or breaking early from a
for_each_available_child_of_node() loop, we need to explicitly call
of_node_put() on the child node to possibly release the node. |
| In the Linux kernel, the following vulnerability has been resolved:
dccp: Fix out of bounds access in DCCP error handler
There was a previous attempt to fix an out-of-bounds access in the DCCP
error handlers, but that fix assumed that the error handlers only want
to access the first 8 bytes of the DCCP header. Actually, they also look
at the DCCP sequence number, which is stored beyond 8 bytes, so an
explicit pskb_may_pull() is required. |
| In the Linux kernel, the following vulnerability has been resolved:
netlink: annotate lockless accesses to nlk->max_recvmsg_len
syzbot reported a data-race in data-race in netlink_recvmsg() [1]
Indeed, netlink_recvmsg() can be run concurrently,
and netlink_dump() also needs protection.
[1]
BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg
read to 0xffff888141840b38 of 8 bytes by task 23057 on cpu 0:
netlink_recvmsg+0xea/0x730 net/netlink/af_netlink.c:1988
sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
__sys_recvfrom+0x1ee/0x2e0 net/socket.c:2194
__do_sys_recvfrom net/socket.c:2212 [inline]
__se_sys_recvfrom net/socket.c:2208 [inline]
__x64_sys_recvfrom+0x78/0x90 net/socket.c:2208
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
write to 0xffff888141840b38 of 8 bytes by task 23037 on cpu 1:
netlink_recvmsg+0x114/0x730 net/netlink/af_netlink.c:1989
sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
____sys_recvmsg+0x156/0x310 net/socket.c:2720
___sys_recvmsg net/socket.c:2762 [inline]
do_recvmmsg+0x2e5/0x710 net/socket.c:2856
__sys_recvmmsg net/socket.c:2935 [inline]
__do_sys_recvmmsg net/socket.c:2958 [inline]
__se_sys_recvmmsg net/socket.c:2951 [inline]
__x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x0000000000000000 -> 0x0000000000001000
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23037 Comm: syz-executor.2 Not tainted 6.3.0-rc4-syzkaller-00195-g5a57b48fdfcb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 |
| In the Linux kernel, the following vulnerability has been resolved:
blk-mq: release crypto keyslot before reporting I/O complete
Once all I/O using a blk_crypto_key has completed, filesystems can call
blk_crypto_evict_key(). However, the block layer currently doesn't call
blk_crypto_put_keyslot() until the request is being freed, which happens
after upper layers have been told (via bio_endio()) the I/O has
completed. This causes a race condition where blk_crypto_evict_key()
can see 'slot_refs != 0' without there being an actual bug.
This makes __blk_crypto_evict_key() hit the
'WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)' and return without
doing anything, eventually causing a use-after-free in
blk_crypto_reprogram_all_keys(). (This is a very rare bug and has only
been seen when per-file keys are being used with fscrypt.)
There are two options to fix this: either release the keyslot before
bio_endio() is called on the request's last bio, or make
__blk_crypto_evict_key() ignore slot_refs. Let's go with the first
solution, since it preserves the ability to report bugs (via
WARN_ON_ONCE) where a key is evicted while still in-use. |
