| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
sh: dma: Fix DMA channel offset calculation
Various SoCs of the SH3, SH4 and SH4A family, which use this driver,
feature a differing number of DMA channels, which can be distributed
between up to two DMAC modules. The existing implementation fails to
correctly accommodate for all those variations, resulting in wrong
channel offset calculations and leading to kernel panics.
Rewrite dma_base_addr() in order to properly calculate channel offsets
in a DMAC module. Fix dmaor_read_reg() and dmaor_write_reg(), so that
the correct DMAC module base is selected for the DMAOR register. |
| In the Linux kernel, the following vulnerability has been resolved:
platform/x86: think-lmi: Fix memory leaks when parsing ThinkStation WMI strings
My previous commit introduced a memory leak where the item allocated
from tlmi_setting was not freed.
This commit also renames it to avoid confusion with the similarly name
variable in the same function. |
| In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: Add check for kmemdup
Since the kmemdup may return NULL pointer,
it should be better to add check for the return value
in order to avoid NULL pointer dereference. |
| In the Linux kernel, the following vulnerability has been resolved:
rcuscale: Move rcu_scale_writer() schedule_timeout_uninterruptible() to _idle()
The rcuscale.holdoff module parameter can be used to delay the start
of rcu_scale_writer() kthread. However, the hung-task timeout will
trigger when the timeout specified by rcuscale.holdoff is greater than
hung_task_timeout_secs:
runqemu kvm nographic slirp qemuparams="-smp 4 -m 2048M"
bootparams="rcuscale.shutdown=0 rcuscale.holdoff=300"
[ 247.071753] INFO: task rcu_scale_write:59 blocked for more than 122 seconds.
[ 247.072529] Not tainted 6.4.0-rc1-00134-gb9ed6de8d4ff #7
[ 247.073400] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 247.074331] task:rcu_scale_write state:D stack:30144 pid:59 ppid:2 flags:0x00004000
[ 247.075346] Call Trace:
[ 247.075660] <TASK>
[ 247.075965] __schedule+0x635/0x1280
[ 247.076448] ? __pfx___schedule+0x10/0x10
[ 247.076967] ? schedule_timeout+0x2dc/0x4d0
[ 247.077471] ? __pfx_lock_release+0x10/0x10
[ 247.078018] ? enqueue_timer+0xe2/0x220
[ 247.078522] schedule+0x84/0x120
[ 247.078957] schedule_timeout+0x2e1/0x4d0
[ 247.079447] ? __pfx_schedule_timeout+0x10/0x10
[ 247.080032] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.080591] ? __pfx_process_timeout+0x10/0x10
[ 247.081163] ? __pfx_sched_set_fifo_low+0x10/0x10
[ 247.081760] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.082287] rcu_scale_writer+0x6b1/0x7f0
[ 247.082773] ? mark_held_locks+0x29/0xa0
[ 247.083252] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.083865] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.084412] kthread+0x179/0x1c0
[ 247.084759] ? __pfx_kthread+0x10/0x10
[ 247.085098] ret_from_fork+0x2c/0x50
[ 247.085433] </TASK>
This commit therefore replaces schedule_timeout_uninterruptible() with
schedule_timeout_idle(). |
| In the Linux kernel, the following vulnerability has been resolved:
ASoC: codecs: tx-macro: Fix for KASAN: slab-out-of-bounds
When we run syzkaller we get below Out of Bound.
"KASAN: slab-out-of-bounds Read in regcache_flat_read"
Below is the backtrace of the issue:
dump_backtrace+0x0/0x4c8
show_stack+0x34/0x44
dump_stack_lvl+0xd8/0x118
print_address_description+0x30/0x2d8
kasan_report+0x158/0x198
__asan_report_load4_noabort+0x44/0x50
regcache_flat_read+0x10c/0x110
regcache_read+0xf4/0x180
_regmap_read+0xc4/0x278
_regmap_update_bits+0x130/0x290
regmap_update_bits_base+0xc0/0x15c
snd_soc_component_update_bits+0xa8/0x22c
snd_soc_component_write_field+0x68/0xd4
tx_macro_digital_mute+0xec/0x140
Actually There is no need to have decimator with 32 bits.
By limiting the variable with short type u8 issue is resolved. |
| In the Linux kernel, the following vulnerability has been resolved:
PCI/DOE: Fix destroy_work_on_stack() race
The following debug object splat was observed in testing:
ODEBUG: free active (active state 0) object: 0000000097d23782 object type: work_struct hint: doe_statemachine_work+0x0/0x510
WARNING: CPU: 1 PID: 71 at lib/debugobjects.c:514 debug_print_object+0x7d/0xb0
...
Workqueue: pci 0000:36:00.0 DOE [1 doe_statemachine_work
RIP: 0010:debug_print_object+0x7d/0xb0
...
Call Trace:
? debug_print_object+0x7d/0xb0
? __pfx_doe_statemachine_work+0x10/0x10
debug_object_free.part.0+0x11b/0x150
doe_statemachine_work+0x45e/0x510
process_one_work+0x1d4/0x3c0
This occurs because destroy_work_on_stack() was called after signaling
the completion in the calling thread. This creates a race between
destroy_work_on_stack() and the task->work struct going out of scope in
pci_doe().
Signal the work complete after destroying the work struct. This is safe
because signal_task_complete() is the final thing the work item does and
the workqueue code is careful not to access the work struct after. |
| In the Linux kernel, the following vulnerability has been resolved:
m68k: Only force 030 bus error if PC not in exception table
__get_kernel_nofault() does copy data in supervisor mode when
forcing a task backtrace log through /proc/sysrq_trigger.
This is expected cause a bus error exception on e.g. NULL
pointer dereferencing when logging a kernel task has no
workqueue associated. This bus error ought to be ignored.
Our 030 bus error handler is ill equipped to deal with this:
Whenever ssw indicates a kernel mode access on a data fault,
we don't even attempt to handle the fault and instead always
send a SEGV signal (or panic). As a result, the check
for exception handling at the fault PC (buried in
send_sig_fault() which gets called from do_page_fault()
eventually) is never used.
In contrast, both 040 and 060 access error handlers do not
care whether a fault happened on supervisor mode access,
and will call do_page_fault() on those, ultimately honoring
the exception table.
Add a check in bus_error030 to call do_page_fault() in case
we do have an entry for the fault PC in our exception table.
I had attempted a fix for this earlier in 2019 that did rely
on testing pagefault_disabled() (see link below) to achieve
the same thing, but this patch should be more generic.
Tested on 030 Atari Falcon. |
| In the Linux kernel, the following vulnerability has been resolved:
net: libwx: fix memory leak in wx_setup_rx_resources
When wx_alloc_page_pool() failed in wx_setup_rx_resources(), it doesn't
release DMA buffer. Add dma_free_coherent() in the error path to release
the DMA buffer. |
| In the Linux kernel, the following vulnerability has been resolved:
regulator: raa215300: Fix resource leak in case of error
The clk_register_clkdev() allocates memory by calling vclkdev_alloc() and
this memory is not freed in the error path. Similarly, resources allocated
by clk_register_fixed_rate() are not freed in the error path.
Fix these issues by using devm_clk_hw_register_fixed_rate() and
devm_clk_hw_register_clkdev().
After this, the static variable clk is not needed. Replace it withÂ
local variable hw in probe() and drop calling clk_unregister_fixed_rate()
from raa215300_rtc_unregister_device(). |
| In the Linux kernel, the following vulnerability has been resolved:
blk-mq: fix tags leak when shrink nr_hw_queues
Although we don't need to realloc set->tags[] when shrink nr_hw_queues,
we need to free them. Or these tags will be leaked.
How to reproduce:
1. mount -t configfs configfs /mnt
2. modprobe null_blk nr_devices=0 submit_queues=8
3. mkdir /mnt/nullb/nullb0
4. echo 1 > /mnt/nullb/nullb0/power
5. echo 4 > /mnt/nullb/nullb0/submit_queues
6. rmdir /mnt/nullb/nullb0
In step 4, will alloc 9 tags (8 submit queues and 1 poll queue), then
in step 5, new_nr_hw_queues = 5 (4 submit queues and 1 poll queue).
At last in step 6, only these 5 tags are freed, the other 4 tags leaked. |
| In the Linux kernel, the following vulnerability has been resolved:
net: ipa: only reset hashed tables when supported
Last year, the code that manages GSI channel transactions switched
from using spinlock-protected linked lists to using indexes into the
ring buffer used for a channel. Recently, Google reported seeing
transaction reference count underflows occasionally during shutdown.
Doug Anderson found a way to reproduce the issue reliably, and
bisected the issue to the commit that eliminated the linked lists
and the lock. The root cause was ultimately determined to be
related to unused transactions being committed as part of the modem
shutdown cleanup activity. Unused transactions are not normally
expected (except in error cases).
The modem uses some ranges of IPA-resident memory, and whenever it
shuts down we zero those ranges. In ipa_filter_reset_table() a
transaction is allocated to zero modem filter table entries. If
hashing is not supported, hashed table memory should not be zeroed.
But currently nothing prevents that, and the result is an unused
transaction. Something similar occurs when we zero routing table
entries for the modem.
By preventing any attempt to clear hashed tables when hashing is not
supported, the reference count underflow is avoided in this case.
Note that there likely remains an issue with properly freeing unused
transactions (if they occur due to errors). This patch addresses
only the underflows that Google originally reported. |
| In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: xsk: Fix invalid buffer access for legacy rq
The below crash can be encountered when using xdpsock in rx mode for
legacy rq: the buffer gets released in the XDP_REDIRECT path, and then
once again in the driver. This fix sets the flag to avoid releasing on
the driver side.
XSK handling of buffers for legacy rq was relying on the caller to set
the skip release flag. But the referenced fix started using fragment
counts for pages instead of the skip flag.
Crash log:
general protection fault, probably for non-canonical address 0xffff8881217e3a: 0000 [#1] SMP
CPU: 0 PID: 14 Comm: ksoftirqd/0 Not tainted 6.5.0-rc1+ #31
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:bpf_prog_03b13f331978c78c+0xf/0x28
Code: ...
RSP: 0018:ffff88810082fc98 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888138404901 RCX: c0ffffc900027cbc
RDX: ffffffffa000b514 RSI: 00ffff8881217e32 RDI: ffff888138404901
RBP: ffff88810082fc98 R08: 0000000000091100 R09: 0000000000000006
R10: 0000000000000800 R11: 0000000000000800 R12: ffffc9000027a000
R13: ffff8881217e2dc0 R14: ffff8881217e2910 R15: ffff8881217e2f00
FS: 0000000000000000(0000) GS:ffff88852c800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564cb2e2cde0 CR3: 000000010e603004 CR4: 0000000000370eb0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
? die_addr+0x32/0x80
? exc_general_protection+0x192/0x390
? asm_exc_general_protection+0x22/0x30
? 0xffffffffa000b514
? bpf_prog_03b13f331978c78c+0xf/0x28
mlx5e_xdp_handle+0x48/0x670 [mlx5_core]
? dev_gro_receive+0x3b5/0x6e0
mlx5e_xsk_skb_from_cqe_linear+0x6e/0x90 [mlx5_core]
mlx5e_handle_rx_cqe+0x55/0x100 [mlx5_core]
mlx5e_poll_rx_cq+0x87/0x6e0 [mlx5_core]
mlx5e_napi_poll+0x45e/0x6b0 [mlx5_core]
__napi_poll+0x25/0x1a0
net_rx_action+0x28a/0x300
__do_softirq+0xcd/0x279
? sort_range+0x20/0x20
run_ksoftirqd+0x1a/0x20
smpboot_thread_fn+0xa2/0x130
kthread+0xc9/0xf0
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30
</TASK>
Modules linked in: mlx5_ib mlx5_core rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm ib_uverbs ib_core xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat br_netfilter overlay zram zsmalloc fuse [last unloaded: mlx5_core]
---[ end trace 0000000000000000 ]--- |
| In the Linux kernel, the following vulnerability has been resolved:
hte: tegra-194: Fix off by one in tegra_hte_map_to_line_id()
The "map_sz" is the number of elements in the "m" array so the >
comparison needs to be changed to >= to prevent an out of bounds
read. |
| In the Linux kernel, the following vulnerability has been resolved:
clk: imx93: fix memory leak and missing unwind goto in imx93_clocks_probe
In function probe(), it returns directly without unregistered hws
when error occurs.
Fix this by adding 'goto unregister_hws;' on line 295 and
line 310.
Use devm_kzalloc() instead of kzalloc() to automatically
free the memory using devm_kfree() when error occurs.
Replace of_iomap() with devm_of_iomap() to automatically
handle the unused ioremap region and delete 'iounmap(anatop_base);'
in unregister_hws. |
| In the Linux kernel, the following vulnerability has been resolved:
serial: 8250: Fix oops for port->pm on uart_change_pm()
Unloading a hardware specific 8250 driver can produce error "Unable to
handle kernel paging request at virtual address" about ten seconds after
unloading the driver. This happens on uart_hangup() calling
uart_change_pm().
Turns out commit 04e82793f068 ("serial: 8250: Reinit port->pm on port
specific driver unbind") was only a partial fix. If the hardware specific
driver has initialized port->pm function, we need to clear port->pm too.
Just reinitializing port->ops does not do this. Otherwise serial8250_pm()
will call port->pm() instead of serial8250_do_pm(). |
| In the Linux kernel, the following vulnerability has been resolved:
net: Fix load-tearing on sk->sk_stamp in sock_recv_cmsgs().
KCSAN found a data race in sock_recv_cmsgs() where the read access
to sk->sk_stamp needs READ_ONCE().
BUG: KCSAN: data-race in packet_recvmsg / packet_recvmsg
write (marked) to 0xffff88803c81f258 of 8 bytes by task 19171 on cpu 0:
sock_write_timestamp include/net/sock.h:2670 [inline]
sock_recv_cmsgs include/net/sock.h:2722 [inline]
packet_recvmsg+0xb97/0xd00 net/packet/af_packet.c:3489
sock_recvmsg_nosec net/socket.c:1019 [inline]
sock_recvmsg+0x11a/0x130 net/socket.c:1040
sock_read_iter+0x176/0x220 net/socket.c:1118
call_read_iter include/linux/fs.h:1845 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x5e0/0x630 fs/read_write.c:470
ksys_read+0x163/0x1a0 fs/read_write.c:613
__do_sys_read fs/read_write.c:623 [inline]
__se_sys_read fs/read_write.c:621 [inline]
__x64_sys_read+0x41/0x50 fs/read_write.c:621
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x72/0xdc
read to 0xffff88803c81f258 of 8 bytes by task 19183 on cpu 1:
sock_recv_cmsgs include/net/sock.h:2721 [inline]
packet_recvmsg+0xb64/0xd00 net/packet/af_packet.c:3489
sock_recvmsg_nosec net/socket.c:1019 [inline]
sock_recvmsg+0x11a/0x130 net/socket.c:1040
sock_read_iter+0x176/0x220 net/socket.c:1118
call_read_iter include/linux/fs.h:1845 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x5e0/0x630 fs/read_write.c:470
ksys_read+0x163/0x1a0 fs/read_write.c:613
__do_sys_read fs/read_write.c:623 [inline]
__se_sys_read fs/read_write.c:621 [inline]
__x64_sys_read+0x41/0x50 fs/read_write.c:621
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x72/0xdc
value changed: 0xffffffffc4653600 -> 0x0000000000000000
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19183 Comm: syz-executor.5 Not tainted 6.3.0-rc7-02330-gca6270c12e20 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 |
| In the Linux kernel, the following vulnerability has been resolved:
Revert "drm/msm: Add missing check and destroy for alloc_ordered_workqueue"
This reverts commit 643b7d0869cc7f1f7a5ac7ca6bd25d88f54e31d0.
A recent patch that tried to fix up the msm_drm_init() paths with
respect to the workqueue but only ended up making things worse:
First, the newly added calls to msm_drm_uninit() on early errors would
trigger NULL-pointer dereferences, for example, as the kms pointer would
not have been initialised. (Note that these paths were also modified by
a second broken error handling patch which in effect cancelled out this
part when merged.)
Second, the newly added allocation sanity check would still leak the
previously allocated drm device.
Instead of trying to salvage what was badly broken (and clearly not
tested), let's revert the bad commit so that clean and backportable
fixes can be added in its place.
Patchwork: https://patchwork.freedesktop.org/patch/525107/ |
| In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: TC, Fix using eswitch mapping in nic mode
Cited patch is using the eswitch object mapping pool while
in nic mode where it isn't initialized. This results in the
trace below [0].
Fix that by using either nic or eswitch object mapping pool
depending if eswitch is enabled or not.
[0]:
[ 826.446057] ==================================================================
[ 826.446729] BUG: KASAN: slab-use-after-free in mlx5_add_flow_rules+0x30/0x490 [mlx5_core]
[ 826.447515] Read of size 8 at addr ffff888194485830 by task tc/6233
[ 826.448243] CPU: 16 PID: 6233 Comm: tc Tainted: G W 6.3.0-rc6+ #1
[ 826.448890] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[ 826.449785] Call Trace:
[ 826.450052] <TASK>
[ 826.450302] dump_stack_lvl+0x33/0x50
[ 826.450650] print_report+0xc2/0x610
[ 826.450998] ? __virt_addr_valid+0xb1/0x130
[ 826.451385] ? mlx5_add_flow_rules+0x30/0x490 [mlx5_core]
[ 826.451935] kasan_report+0xae/0xe0
[ 826.452276] ? mlx5_add_flow_rules+0x30/0x490 [mlx5_core]
[ 826.452829] mlx5_add_flow_rules+0x30/0x490 [mlx5_core]
[ 826.453368] ? __kmalloc_node+0x5a/0x120
[ 826.453733] esw_add_restore_rule+0x20f/0x270 [mlx5_core]
[ 826.454288] ? mlx5_eswitch_add_send_to_vport_meta_rule+0x260/0x260 [mlx5_core]
[ 826.455011] ? mutex_unlock+0x80/0xd0
[ 826.455361] ? __mutex_unlock_slowpath.constprop.0+0x210/0x210
[ 826.455862] ? mapping_add+0x2cb/0x440 [mlx5_core]
[ 826.456425] mlx5e_tc_action_miss_mapping_get+0x139/0x180 [mlx5_core]
[ 826.457058] ? mlx5e_tc_update_skb_nic+0xb0/0xb0 [mlx5_core]
[ 826.457636] ? __kasan_kmalloc+0x77/0x90
[ 826.458000] ? __kmalloc+0x57/0x120
[ 826.458336] mlx5_tc_ct_flow_offload+0x325/0xe40 [mlx5_core]
[ 826.458916] ? ct_kernel_enter.constprop.0+0x48/0xa0
[ 826.459360] ? mlx5_tc_ct_parse_action+0xf0/0xf0 [mlx5_core]
[ 826.459933] ? mlx5e_mod_hdr_attach+0x491/0x520 [mlx5_core]
[ 826.460507] ? mlx5e_mod_hdr_get+0x12/0x20 [mlx5_core]
[ 826.461046] ? mlx5e_tc_attach_mod_hdr+0x154/0x170 [mlx5_core]
[ 826.461635] mlx5e_configure_flower+0x969/0x2110 [mlx5_core]
[ 826.462217] ? _raw_spin_lock_bh+0x85/0xe0
[ 826.462597] ? __mlx5e_add_fdb_flow+0x750/0x750 [mlx5_core]
[ 826.463163] ? kasan_save_stack+0x2e/0x40
[ 826.463534] ? down_read+0x115/0x1b0
[ 826.463878] ? down_write_killable+0x110/0x110
[ 826.464288] ? tc_setup_action.part.0+0x9f/0x3b0
[ 826.464701] ? mlx5e_is_uplink_rep+0x4c/0x90 [mlx5_core]
[ 826.465253] ? mlx5e_tc_reoffload_flows_work+0x130/0x130 [mlx5_core]
[ 826.465878] tc_setup_cb_add+0x112/0x250
[ 826.466247] fl_hw_replace_filter+0x230/0x310 [cls_flower]
[ 826.466724] ? fl_hw_destroy_filter+0x1a0/0x1a0 [cls_flower]
[ 826.467212] fl_change+0x14e1/0x2030 [cls_flower]
[ 826.467636] ? sock_def_readable+0x89/0x120
[ 826.468019] ? fl_tmplt_create+0x2d0/0x2d0 [cls_flower]
[ 826.468509] ? kasan_unpoison+0x23/0x50
[ 826.468873] ? get_random_u16+0x180/0x180
[ 826.469244] ? __radix_tree_lookup+0x2b/0x130
[ 826.469640] ? fl_get+0x7b/0x140 [cls_flower]
[ 826.470042] ? fl_mask_put+0x200/0x200 [cls_flower]
[ 826.470478] ? __mutex_unlock_slowpath.constprop.0+0x210/0x210
[ 826.470973] ? fl_tmplt_create+0x2d0/0x2d0 [cls_flower]
[ 826.471427] tc_new_tfilter+0x644/0x1050
[ 826.471795] ? tc_get_tfilter+0x860/0x860
[ 826.472170] ? __thaw_task+0x130/0x130
[ 826.472525] ? arch_stack_walk+0x98/0xf0
[ 826.472892] ? cap_capable+0x9f/0xd0
[ 826.473235] ? security_capable+0x47/0x60
[ 826.473608] rtnetlink_rcv_msg+0x1d5/0x550
[ 826.473985] ? rtnl_calcit.isra.0+0x1f0/0x1f0
[ 826.474383] ? __stack_depot_save+0x35/0x4c0
[ 826.474779] ? kasan_save_stack+0x2e/0x40
[ 826.475149] ? kasan_save_stack+0x1e/0x40
[ 826.475518] ? __kasan_record_aux_stack+0x9f/0xb0
[ 826.475939] ? task_work_add+0x77/0x1c0
[ 826.476305] netlink_rcv_skb+0xe0/0x210
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
virtio-vdpa: Fix cpumask memory leak in virtio_vdpa_find_vqs()
Free the cpumask allocated by create_affinity_masks() before returning
from the function. |
| In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix potential user-after-free
This fixes all instances of which requires to allocate a buffer calling
alloc_skb which may release the chan lock and reacquire later which
makes it possible that the chan is disconnected in the meantime. |
