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CVSS v3.1 |
In the Linux kernel, the following vulnerability has been resolved:
ACPICA: Fix use-after-free in acpi_ut_copy_ipackage_to_ipackage()
There is an use-after-free reported by KASAN:
BUG: KASAN: use-after-free in acpi_ut_remove_reference+0x3b/0x82
Read of size 1 at addr ffff888112afc460 by task modprobe/2111
CPU: 0 PID: 2111 Comm: modprobe Not tainted 6.1.0-rc7-dirty
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
Call Trace:
<TASK>
kasan_report+0xae/0xe0
acpi_ut_remove_reference+0x3b/0x82
acpi_ut_copy_iobject_to_iobject+0x3be/0x3d5
acpi_ds_store_object_to_local+0x15d/0x3a0
acpi_ex_store+0x78d/0x7fd
acpi_ex_opcode_1A_1T_1R+0xbe4/0xf9b
acpi_ps_parse_aml+0x217/0x8d5
...
</TASK>
The root cause of the problem is that the acpi_operand_object
is freed when acpi_ut_walk_package_tree() fails in
acpi_ut_copy_ipackage_to_ipackage(), lead to repeated release in
acpi_ut_copy_iobject_to_iobject(). The problem was introduced
by "8aa5e56eeb61" commit, this commit is to fix memory leak in
acpi_ut_copy_iobject_to_iobject(), repeatedly adding remove
operation, lead to "acpi_operand_object" used after free.
Fix it by removing acpi_ut_remove_reference() in
acpi_ut_copy_ipackage_to_ipackage(). acpi_ut_copy_ipackage_to_ipackage()
is called to copy an internal package object into another internal
package object, when it fails, the memory of acpi_operand_object
should be freed by the caller. |
In the Linux kernel, the following vulnerability has been resolved:
drm/amdkfd: Fix UBSAN shift-out-of-bounds warning
If get_num_sdma_queues or get_num_xgmi_sdma_queues is 0, we end up
doing a shift operation where the number of bits shifted equals
number of bits in the operand. This behaviour is undefined.
Set num_sdma_queues or num_xgmi_sdma_queues to ULLONG_MAX, if the
count is >= number of bits in the operand.
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1472 |
In the Linux kernel, the following vulnerability has been resolved:
fbdev: imxfb: Removed unneeded release_mem_region
Remove unnecessary release_mem_region from the error path to prevent
mem region from being released twice, which could avoid resource leak
or other unexpected issues. |
In the Linux kernel, the following vulnerability has been resolved:
pwm: lpc32xx: Remove handling of PWM channels
Because LPC32xx PWM controllers have only a single output which is
registered as the only PWM device/channel per controller, it is known in
advance that pwm->hwpwm value is always 0. On basis of this fact
simplify the code by removing operations with pwm->hwpwm, there is no
controls which require channel number as input.
Even though I wasn't aware at the time when I forward ported that patch,
this fixes a null pointer dereference as lpc32xx->chip.pwms is NULL
before devm_pwmchip_add() is called. |
In the Linux kernel, the following vulnerability has been resolved:
ipv6: Add lwtunnel encap size of all siblings in nexthop calculation
In function rt6_nlmsg_size(), the length of nexthop is calculated
by multipling the nexthop length of fib6_info and the number of
siblings. However if the fib6_info has no lwtunnel but the siblings
have lwtunnels, the nexthop length is less than it should be, and
it will trigger a warning in inet6_rt_notify() as follows:
WARNING: CPU: 0 PID: 6082 at net/ipv6/route.c:6180 inet6_rt_notify+0x120/0x130
......
Call Trace:
<TASK>
fib6_add_rt2node+0x685/0xa30
fib6_add+0x96/0x1b0
ip6_route_add+0x50/0xd0
inet6_rtm_newroute+0x97/0xa0
rtnetlink_rcv_msg+0x156/0x3d0
netlink_rcv_skb+0x5a/0x110
netlink_unicast+0x246/0x350
netlink_sendmsg+0x250/0x4c0
sock_sendmsg+0x66/0x70
___sys_sendmsg+0x7c/0xd0
__sys_sendmsg+0x5d/0xb0
do_syscall_64+0x3f/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
This bug can be reproduced by script:
ip -6 addr add 2002::2/64 dev ens2
ip -6 route add 100::/64 via 2002::1 dev ens2 metric 100
for i in 10 20 30 40 50 60 70;
do
ip link add link ens2 name ipv_$i type ipvlan
ip -6 addr add 2002::$i/64 dev ipv_$i
ifconfig ipv_$i up
done
for i in 10 20 30 40 50 60;
do
ip -6 route append 100::/64 encap ip6 dst 2002::$i via 2002::1
dev ipv_$i metric 100
done
ip -6 route append 100::/64 via 2002::1 dev ipv_70 metric 100
This patch fixes it by adding nexthop_len of every siblings using
rt6_nh_nlmsg_size(). |
In the Linux kernel, the following vulnerability has been resolved:
memory: of: Fix refcount leak bug in of_lpddr3_get_ddr_timings()
We should add the of_node_put() when breaking out of
for_each_child_of_node() as it will automatically increase
and decrease the refcount. |
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_conn: Fix crash on hci_create_cis_sync
When attempting to connect multiple ISO sockets without using
DEFER_SETUP may result in the following crash:
BUG: KASAN: null-ptr-deref in hci_create_cis_sync+0x18b/0x2b0
Read of size 2 at addr 0000000000000036 by task kworker/u3:1/50
CPU: 0 PID: 50 Comm: kworker/u3:1 Not tainted
6.0.0-rc7-02243-gb84a13ff4eda #4373
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS 1.16.0-1.fc36 04/01/2014
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
<TASK>
dump_stack_lvl+0x19/0x27
kasan_report+0xbc/0xf0
? hci_create_cis_sync+0x18b/0x2b0
hci_create_cis_sync+0x18b/0x2b0
? get_link_mode+0xd0/0xd0
? __ww_mutex_lock_slowpath+0x10/0x10
? mutex_lock+0xe0/0xe0
? get_link_mode+0xd0/0xd0
hci_cmd_sync_work+0x111/0x190
process_one_work+0x427/0x650
worker_thread+0x87/0x750
? process_one_work+0x650/0x650
kthread+0x14e/0x180
? kthread_exit+0x50/0x50
ret_from_fork+0x22/0x30
</TASK> |
In the Linux kernel, the following vulnerability has been resolved:
drm/vc4: drop all currently held locks if deadlock happens
If vc4_hdmi_reset_link() returns -EDEADLK, it means that a deadlock
happened in the locking context. This situation should be addressed by
dropping all currently held locks and block until the contended lock
becomes available. Currently, vc4 is not dealing with the deadlock
properly, producing the following output when PROVE_LOCKING is enabled:
[ 825.612809] ------------[ cut here ]------------
[ 825.612852] WARNING: CPU: 1 PID: 116 at drivers/gpu/drm/drm_modeset_lock.c:276 drm_modeset_drop_locks+0x60/0x68 [drm]
[ 825.613458] Modules linked in: 8021q mrp garp stp llc
raspberrypi_cpufreq brcmfmac brcmutil crct10dif_ce hci_uart cfg80211
btqca btbcm bluetooth vc4 raspberrypi_hwmon snd_soc_hdmi_codec cec
clk_raspberrypi ecdh_generic drm_display_helper ecc rfkill
drm_dma_helper drm_kms_helper pwm_bcm2835 bcm2835_thermal bcm2835_rng
rng_core i2c_bcm2835 drm fuse ip_tables x_tables ipv6
[ 825.613735] CPU: 1 PID: 116 Comm: kworker/1:2 Tainted: G W 6.1.0-rc6-01399-g941aae326315 #3
[ 825.613759] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
[ 825.613777] Workqueue: events output_poll_execute [drm_kms_helper]
[ 825.614038] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 825.614063] pc : drm_modeset_drop_locks+0x60/0x68 [drm]
[ 825.614603] lr : drm_helper_probe_detect+0x120/0x1b4 [drm_kms_helper]
[ 825.614829] sp : ffff800008313bf0
[ 825.614844] x29: ffff800008313bf0 x28: ffffcd7778b8b000 x27: 0000000000000000
[ 825.614883] x26: 0000000000000001 x25: 0000000000000001 x24: ffff677cc35c2758
[ 825.614920] x23: ffffcd7707d01430 x22: ffffcd7707c3edc7 x21: 0000000000000001
[ 825.614958] x20: 0000000000000000 x19: ffff800008313c10 x18: 000000000000b6d3
[ 825.614995] x17: ffffcd777835e214 x16: ffffcd7777cef870 x15: fffff81000000000
[ 825.615033] x14: 0000000000000000 x13: 0000000000000099 x12: 0000000000000002
[ 825.615070] x11: 72917988020af800 x10: 72917988020af800 x9 : 72917988020af800
[ 825.615108] x8 : ffff677cc665e0a8 x7 : d00a8c180000110c x6 : ffffcd77774c0054
[ 825.615145] x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
[ 825.615181] x2 : ffff677cc55e1880 x1 : ffffcd7777cef8ec x0 : ffff800008313c10
[ 825.615219] Call trace:
[ 825.615232] drm_modeset_drop_locks+0x60/0x68 [drm]
[ 825.615773] drm_helper_probe_detect+0x120/0x1b4 [drm_kms_helper]
[ 825.616003] output_poll_execute+0xe4/0x224 [drm_kms_helper]
[ 825.616233] process_one_work+0x2b4/0x618
[ 825.616264] worker_thread+0x24c/0x464
[ 825.616288] kthread+0xec/0x110
[ 825.616310] ret_from_fork+0x10/0x20
[ 825.616335] irq event stamp: 7634
[ 825.616349] hardirqs last enabled at (7633): [<ffffcd777831ee90>] _raw_spin_unlock_irq+0x3c/0x78
[ 825.616384] hardirqs last disabled at (7634): [<ffffcd7778315a78>] __schedule+0x134/0x9f0
[ 825.616411] softirqs last enabled at (7630): [<ffffcd7707aacea0>] local_bh_enable+0x4/0x30 [ipv6]
[ 825.617019] softirqs last disabled at (7618): [<ffffcd7707aace70>] local_bh_disable+0x4/0x30 [ipv6]
[ 825.617586] ---[ end trace 0000000000000000 ]---
Therefore, deal with the deadlock as suggested by [1], using the
function drm_modeset_backoff().
[1] https://docs.kernel.org/gpu/drm-kms.html?highlight=kms#kms-locking |
In the Linux kernel, the following vulnerability has been resolved:
ubi: ubi_wl_put_peb: Fix infinite loop when wear-leveling work failed
Following process will trigger an infinite loop in ubi_wl_put_peb():
ubifs_bgt ubi_bgt
ubifs_leb_unmap
ubi_leb_unmap
ubi_eba_unmap_leb
ubi_wl_put_peb wear_leveling_worker
e1 = rb_entry(rb_first(&ubi->used)
e2 = get_peb_for_wl(ubi)
ubi_io_read_vid_hdr // return err (flash fault)
out_error:
ubi->move_from = ubi->move_to = NULL
wl_entry_destroy(ubi, e1)
ubi->lookuptbl[e->pnum] = NULL
retry:
e = ubi->lookuptbl[pnum]; // return NULL
if (e == ubi->move_from) { // NULL == NULL gets true
goto retry; // infinite loop !!!
$ top
PID USER PR NI VIRT RES SHR S %CPU %MEM COMMAND
7676 root 20 0 0 0 0 R 100.0 0.0 ubifs_bgt0_0
Fix it by:
1) Letting ubi_wl_put_peb() returns directly if wearl leveling entry has
been removed from 'ubi->lookuptbl'.
2) Using 'ubi->wl_lock' protecting wl entry deletion to preventing an
use-after-free problem for wl entry in ubi_wl_put_peb().
Fetch a reproducer in [Link]. |
In the Linux kernel, the following vulnerability has been resolved:
s390/dasd: Fix potential memleak in dasd_eckd_init()
`dasd_reserve_req` is allocated before `dasd_vol_info_req`, and it
also needs to be freed before the error returns, just like the other
cases in this function. |
In the Linux kernel, the following vulnerability has been resolved:
drm/rockchip: lvds: fix PM usage counter unbalance in poweron
pm_runtime_get_sync will increment pm usage counter even it failed.
Forgetting to putting operation will result in reference leak here.
We fix it by replacing it with the newest pm_runtime_resume_and_get
to keep usage counter balanced. |
In the Linux kernel, the following vulnerability has been resolved:
hsr: Fix uninit-value access in fill_frame_info()
Syzbot reports the following uninit-value access problem.
=====================================================
BUG: KMSAN: uninit-value in fill_frame_info net/hsr/hsr_forward.c:601 [inline]
BUG: KMSAN: uninit-value in hsr_forward_skb+0x9bd/0x30f0 net/hsr/hsr_forward.c:616
fill_frame_info net/hsr/hsr_forward.c:601 [inline]
hsr_forward_skb+0x9bd/0x30f0 net/hsr/hsr_forward.c:616
hsr_dev_xmit+0x192/0x330 net/hsr/hsr_device.c:223
__netdev_start_xmit include/linux/netdevice.h:4889 [inline]
netdev_start_xmit include/linux/netdevice.h:4903 [inline]
xmit_one net/core/dev.c:3544 [inline]
dev_hard_start_xmit+0x247/0xa10 net/core/dev.c:3560
__dev_queue_xmit+0x34d0/0x52a0 net/core/dev.c:4340
dev_queue_xmit include/linux/netdevice.h:3082 [inline]
packet_xmit+0x9c/0x6b0 net/packet/af_packet.c:276
packet_snd net/packet/af_packet.c:3087 [inline]
packet_sendmsg+0x8b1d/0x9f30 net/packet/af_packet.c:3119
sock_sendmsg_nosec net/socket.c:730 [inline]
sock_sendmsg net/socket.c:753 [inline]
__sys_sendto+0x781/0xa30 net/socket.c:2176
__do_sys_sendto net/socket.c:2188 [inline]
__se_sys_sendto net/socket.c:2184 [inline]
__ia32_sys_sendto+0x11f/0x1c0 net/socket.c:2184
do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
__do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
do_fast_syscall_32+0x37/0x80 arch/x86/entry/common.c:203
do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:246
entry_SYSENTER_compat_after_hwframe+0x70/0x82
Uninit was created at:
slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
slab_alloc_node mm/slub.c:3478 [inline]
kmem_cache_alloc_node+0x577/0xa80 mm/slub.c:3523
kmalloc_reserve+0x148/0x470 net/core/skbuff.c:559
__alloc_skb+0x318/0x740 net/core/skbuff.c:644
alloc_skb include/linux/skbuff.h:1286 [inline]
alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6299
sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2794
packet_alloc_skb net/packet/af_packet.c:2936 [inline]
packet_snd net/packet/af_packet.c:3030 [inline]
packet_sendmsg+0x70e8/0x9f30 net/packet/af_packet.c:3119
sock_sendmsg_nosec net/socket.c:730 [inline]
sock_sendmsg net/socket.c:753 [inline]
__sys_sendto+0x781/0xa30 net/socket.c:2176
__do_sys_sendto net/socket.c:2188 [inline]
__se_sys_sendto net/socket.c:2184 [inline]
__ia32_sys_sendto+0x11f/0x1c0 net/socket.c:2184
do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
__do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
do_fast_syscall_32+0x37/0x80 arch/x86/entry/common.c:203
do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:246
entry_SYSENTER_compat_after_hwframe+0x70/0x82
It is because VLAN not yet supported in hsr driver. Return error
when protocol is ETH_P_8021Q in fill_frame_info() now to fix it. |
In the Linux kernel, the following vulnerability has been resolved:
scsi: qla4xxx: Add length check when parsing nlattrs
There are three places that qla4xxx parses nlattrs:
- qla4xxx_set_chap_entry()
- qla4xxx_iface_set_param()
- qla4xxx_sysfs_ddb_set_param()
and each of them directly converts the nlattr to specific pointer of
structure without length checking. This could be dangerous as those
attributes are not validated and a malformed nlattr (e.g., length 0) could
result in an OOB read that leaks heap dirty data.
Add the nla_len check before accessing the nlattr data and return EINVAL if
the length check fails. |
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix off-by-one errors in fast-commit block filling
Due to several different off-by-one errors, or perhaps due to a late
change in design that wasn't fully reflected in the code that was
actually merged, there are several very strange constraints on how
fast-commit blocks are filled with tlv entries:
- tlvs must start at least 10 bytes before the end of the block, even
though the minimum tlv length is 8. Otherwise, the replay code will
ignore them. (BUG: ext4_fc_reserve_space() could violate this
requirement if called with a len of blocksize - 9 or blocksize - 8.
Fortunately, this doesn't seem to happen currently.)
- tlvs must end at least 1 byte before the end of the block. Otherwise
the replay code will consider them to be invalid. This quirk
contributed to a bug (fixed by an earlier commit) where uninitialized
memory was being leaked to disk in the last byte of blocks.
Also, strangely these constraints don't apply to the replay code in
e2fsprogs, which will accept any tlvs in the blocks (with no bounds
checks at all, but that is a separate issue...).
Given that this all seems to be a bug, let's fix it by just filling
blocks with tlv entries in the natural way.
Note that old kernels will be unable to replay fast-commit journals
created by kernels that have this commit. |
In the Linux kernel, the following vulnerability has been resolved:
blk-mq: fix possible memleak when register 'hctx' failed
There's issue as follows when do fault injection test:
unreferenced object 0xffff888132a9f400 (size 512):
comm "insmod", pid 308021, jiffies 4324277909 (age 509.733s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 08 f4 a9 32 81 88 ff ff ...........2....
08 f4 a9 32 81 88 ff ff 00 00 00 00 00 00 00 00 ...2............
backtrace:
[<00000000e8952bb4>] kmalloc_node_trace+0x22/0xa0
[<00000000f9980e0f>] blk_mq_alloc_and_init_hctx+0x3f1/0x7e0
[<000000002e719efa>] blk_mq_realloc_hw_ctxs+0x1e6/0x230
[<000000004f1fda40>] blk_mq_init_allocated_queue+0x27e/0x910
[<00000000287123ec>] __blk_mq_alloc_disk+0x67/0xf0
[<00000000a2a34657>] 0xffffffffa2ad310f
[<00000000b173f718>] 0xffffffffa2af824a
[<0000000095a1dabb>] do_one_initcall+0x87/0x2a0
[<00000000f32fdf93>] do_init_module+0xdf/0x320
[<00000000cbe8541e>] load_module+0x3006/0x3390
[<0000000069ed1bdb>] __do_sys_finit_module+0x113/0x1b0
[<00000000a1a29ae8>] do_syscall_64+0x35/0x80
[<000000009cd878b0>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
Fault injection context as follows:
kobject_add
blk_mq_register_hctx
blk_mq_sysfs_register
blk_register_queue
device_add_disk
null_add_dev.part.0 [null_blk]
As 'blk_mq_register_hctx' may already add some objects when failed halfway,
but there isn't do fallback, caller don't know which objects add failed.
To solve above issue just do fallback when add objects failed halfway in
'blk_mq_register_hctx'. |
In the Linux kernel, the following vulnerability has been resolved:
scsi: libsas: Fix use-after-free bug in smp_execute_task_sg()
When executing SMP task failed, the smp_execute_task_sg() calls del_timer()
to delete "slow_task->timer". However, if the timer handler
sas_task_internal_timedout() is running, the del_timer() in
smp_execute_task_sg() will not stop it and a UAF will happen. The process
is shown below:
(thread 1) | (thread 2)
smp_execute_task_sg() | sas_task_internal_timedout()
... |
del_timer() |
... | ...
sas_free_task(task) |
kfree(task->slow_task) //FREE|
| task->slow_task->... //USE
Fix by calling del_timer_sync() in smp_execute_task_sg(), which makes sure
the timer handler have finished before the "task->slow_task" is
deallocated. |
In the Linux kernel, the following vulnerability has been resolved:
powerpc/rtas_flash: allow user copy to flash block cache objects
With hardened usercopy enabled (CONFIG_HARDENED_USERCOPY=y), using the
/proc/powerpc/rtas/firmware_update interface to prepare a system
firmware update yields a BUG():
kernel BUG at mm/usercopy.c:102!
Oops: Exception in kernel mode, sig: 5 [#1]
LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
Modules linked in:
CPU: 0 PID: 2232 Comm: dd Not tainted 6.5.0-rc3+ #2
Hardware name: IBM,8408-E8E POWER8E (raw) 0x4b0201 0xf000004 of:IBM,FW860.50 (SV860_146) hv:phyp pSeries
NIP: c0000000005991d0 LR: c0000000005991cc CTR: 0000000000000000
REGS: c0000000148c76a0 TRAP: 0700 Not tainted (6.5.0-rc3+)
MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 24002242 XER: 0000000c
CFAR: c0000000001fbd34 IRQMASK: 0
[ ... GPRs omitted ... ]
NIP usercopy_abort+0xa0/0xb0
LR usercopy_abort+0x9c/0xb0
Call Trace:
usercopy_abort+0x9c/0xb0 (unreliable)
__check_heap_object+0x1b4/0x1d0
__check_object_size+0x2d0/0x380
rtas_flash_write+0xe4/0x250
proc_reg_write+0xfc/0x160
vfs_write+0xfc/0x4e0
ksys_write+0x90/0x160
system_call_exception+0x178/0x320
system_call_common+0x160/0x2c4
The blocks of the firmware image are copied directly from user memory
to objects allocated from flash_block_cache, so flash_block_cache must
be created using kmem_cache_create_usercopy() to mark it safe for user
access.
[mpe: Trim and indent oops] |
In the Linux kernel, the following vulnerability has been resolved:
ext4: remove a BUG_ON in ext4_mb_release_group_pa()
If a malicious fuzzer overwrites the ext4 superblock while it is
mounted such that the s_first_data_block is set to a very large
number, the calculation of the block group can underflow, and trigger
a BUG_ON check. Change this to be an ext4_warning so that we don't
crash the kernel. |
In the Linux kernel, the following vulnerability has been resolved:
ALSA: ac97: fix possible memory leak in snd_ac97_dev_register()
If device_register() fails in snd_ac97_dev_register(), it should
call put_device() to give up reference, or the name allocated in
dev_set_name() is leaked. |
In the Linux kernel, the following vulnerability has been resolved:
ARC: mm: fix leakage of memory allocated for PTE
Since commit d9820ff ("ARC: mm: switch pgtable_t back to struct page *")
a memory leakage problem occurs. Memory allocated for page table entries
not released during process termination. This issue can be reproduced by
a small program that allocates a large amount of memory. After several
runs, you'll see that the amount of free memory has reduced and will
continue to reduce after each run. All ARC CPUs are effected by this
issue. The issue was introduced since the kernel stable release v5.15-rc1.
As described in commit d9820ff after switch pgtable_t back to struct
page *, a pointer to "struct page" and appropriate functions are used to
allocate and free a memory page for PTEs, but the pmd_pgtable macro hasn't
changed and returns the direct virtual address from the PMD (PGD) entry.
Than this address used as a parameter in the __pte_free() and as a result
this function couldn't release memory page allocated for PTEs.
Fix this issue by changing the pmd_pgtable macro and returning pointer to
struct page. |