Linux: >> Linux Kernel >> 4.19.101 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
ASoC: stm32: sai: fix OF node leak on probe
The reference taken to the sync provider OF node when probing the
platform device is currently only dropped if the set_sync() callback
fails during DAI probe.
Make sure to drop the reference on platform probe failures (e.g. probe
deferral) and on driver unbind.
This also avoids a potential use-after-free in case the DAI is ever
reprobed without first rebinding the platform driver.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: btusb: revert use of devm_kzalloc in btusb
This reverts commit 98921dbd00c4e ("Bluetooth: Use devm_kzalloc in
btusb.c file").
In btusb_probe(), we use devm_kzalloc() to allocate the btusb data. This
ties the lifetime of all the btusb data to the binding of a driver to
one interface, INTF. In a driver that binds to other interfaces, ISOC
and DIAG, this is an accident waiting to happen.
The issue is revealed in btusb_disconnect(), where calling
usb_driver_release_interface(&btusb_driver, data->intf) will have devm
free the data that is also being used by the other interfaces of the
driver that may not be released yet.
To fix this, revert the use of devm and go back to freeing memory
explicitly.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
drm/ttm: Avoid NULL pointer deref for evicted BOs
It is possible for a BO to exist that is not currently associated with a
resource, e.g. because it has been evicted.
When devcoredump tries to read the contents of all BOs for dumping, we need
to expect this as well -- in this case, ENODATA is recorded instead of the
buffer contents.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
Input: lkkbd - disable pending work before freeing device
lkkbd_interrupt() schedules lk->tq via schedule_work(), and the work
handler lkkbd_reinit() dereferences the lkkbd structure and its
serio/input_dev fields.
lkkbd_disconnect() and error paths in lkkbd_connect() free the lkkbd
structure without preventing the reinit work from being queued again
until serio_close() returns. This can allow the work handler to run
after the structure has been freed, leading to a potential use-after-free.
Use disable_work_sync() instead of cancel_work_sync() to ensure the
reinit work cannot be re-queued, and call it both in lkkbd_disconnect()
and in lkkbd_connect() error paths after serio_open().
CVSS Score
7.8
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
functionfs: fix the open/removal races
ffs_epfile_open() can race with removal, ending up with file->private_data
pointing to freed object.
There is a total count of opened files on functionfs (both ep0 and
dynamic ones) and when it hits zero, dynamic files get removed.
Unfortunately, that removal can happen while another thread is
in ffs_epfile_open(), but has not incremented the count yet.
In that case open will succeed, leaving us with UAF on any subsequent
read() or write().
The root cause is that ffs->opened is misused; atomic_dec_and_test() vs.
atomic_add_return() is not a good idea, when object remains visible all
along.
To untangle that
* serialize openers on ffs->mutex (both for ep0 and for dynamic files)
* have dynamic ones use atomic_inc_not_zero() and fail if we had
zero ->opened; in that case the file we are opening is doomed.
* have the inodes of dynamic files marked on removal (from the
callback of simple_recursive_removal()) - clear ->i_private there.
* have open of dynamic ones verify they hadn't been already removed,
along with checking that state is FFS_ACTIVE.
CVSS Score
4.7
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
scsi: aic94xx: fix use-after-free in device removal path
The asd_pci_remove() function fails to synchronize with pending tasklets
before freeing the asd_ha structure, leading to a potential
use-after-free vulnerability.
When a device removal is triggered (via hot-unplug or module unload),
race condition can occur.
The fix adds tasklet_kill() before freeing the asd_ha structure,
ensuring all scheduled tasklets complete before cleanup proceeds.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
driver core: fix potential null-ptr-deref in device_add()
I got the following null-ptr-deref report while doing fault injection test:
BUG: kernel NULL pointer dereference, address: 0000000000000058
CPU: 2 PID: 278 Comm: 37-i2c-ds2482 Tainted: G B W N 6.1.0-rc3+
RIP: 0010:klist_put+0x2d/0xd0
Call Trace:
<TASK>
klist_remove+0xf1/0x1c0
device_release_driver_internal+0x196/0x210
bus_remove_device+0x1bd/0x240
device_add+0xd3d/0x1100
w1_add_master_device+0x476/0x490 [wire]
ds2482_probe+0x303/0x3e0 [ds2482]
This is how it happened:
w1_alloc_dev()
// The dev->driver is set to w1_master_driver.
memcpy(&dev->dev, device, sizeof(struct device));
device_add()
bus_add_device()
dpm_sysfs_add() // It fails, calls bus_remove_device.
// error path
bus_remove_device()
// The dev->driver is not null, but driver is not bound.
__device_release_driver()
klist_remove(&dev->p->knode_driver) <-- It causes null-ptr-deref.
// normal path
bus_probe_device() // It's not called yet.
device_bind_driver()
If dev->driver is set, in the error path after calling bus_add_device()
in device_add(), bus_remove_device() is called, then the device will be
detached from driver. But device_bind_driver() is not called yet, so it
causes null-ptr-deref while access the 'knode_driver'. To fix this, set
dev->driver to null in the error path before calling bus_remove_device().
CVSS Score
5.5
EPSS Score
0.0
Published
2025-12-30
In the Linux kernel, the following vulnerability has been resolved:
HID: uclogic: Correct devm device reference for hidinput input_dev name
Reference the HID device rather than the input device for the devm
allocation of the input_dev name. Referencing the input_dev would lead to a
use-after-free when the input_dev was unregistered and subsequently fires a
uevent that depends on the name. At the point of firing the uevent, the
name would be freed by devres management.
Use devm_kasprintf to simplify the logic for allocating memory and
formatting the input_dev name string.
CVSS Score
7.8
EPSS Score
0.0
Published
2025-12-30
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix racy bitfield write in btrfs_clear_space_info_full()
From the memory-barriers.txt document regarding memory barrier ordering
guarantees:
(*) These guarantees do not apply to bitfields, because compilers often
generate code to modify these using non-atomic read-modify-write
sequences. Do not attempt to use bitfields to synchronize parallel
algorithms.
(*) Even in cases where bitfields are protected by locks, all fields
in a given bitfield must be protected by one lock. If two fields
in a given bitfield are protected by different locks, the compiler's
non-atomic read-modify-write sequences can cause an update to one
field to corrupt the value of an adjacent field.
btrfs_space_info has a bitfield sharing an underlying word consisting of
the fields full, chunk_alloc, and flush:
struct btrfs_space_info {
struct btrfs_fs_info * fs_info; /* 0 8 */
struct btrfs_space_info * parent; /* 8 8 */
...
int clamp; /* 172 4 */
unsigned int full:1; /* 176: 0 4 */
unsigned int chunk_alloc:1; /* 176: 1 4 */
unsigned int flush:1; /* 176: 2 4 */
...
Therefore, to be safe from parallel read-modify-writes losing a write to
one of the bitfield members protected by a lock, all writes to all the
bitfields must use the lock. They almost universally do, except for
btrfs_clear_space_info_full() which iterates over the space_infos and
writes out found->full = 0 without a lock.
Imagine that we have one thread completing a transaction in which we
finished deleting a block_group and are thus calling
btrfs_clear_space_info_full() while simultaneously the data reclaim
ticket infrastructure is running do_async_reclaim_data_space():
T1 T2
btrfs_commit_transaction
btrfs_clear_space_info_full
data_sinfo->full = 0
READ: full:0, chunk_alloc:0, flush:1
do_async_reclaim_data_space(data_sinfo)
spin_lock(&space_info->lock);
if(list_empty(tickets))
space_info->flush = 0;
READ: full: 0, chunk_alloc:0, flush:1
MOD/WRITE: full: 0, chunk_alloc:0, flush:0
spin_unlock(&space_info->lock);
return;
MOD/WRITE: full:0, chunk_alloc:0, flush:1
and now data_sinfo->flush is 1 but the reclaim worker has exited. This
breaks the invariant that flush is 0 iff there is no work queued or
running. Once this invariant is violated, future allocations that go
into __reserve_bytes() will add tickets to space_info->tickets but will
see space_info->flush is set to 1 and not queue the work. After this,
they will block forever on the resulting ticket, as it is now impossible
to kick the worker again.
I also confirmed by looking at the assembly of the affected kernel that
it is doing RMW operations. For example, to set the flush (3rd) bit to 0,
the assembly is:
andb $0xfb,0x60(%rbx)
and similarly for setting the full (1st) bit to 0:
andb $0xfe,-0x20(%rax)
So I think this is really a bug on practical systems. I have observed
a number of systems in this exact state, but am currently unable to
reproduce it.
Rather than leaving this footgun lying around for the future, take
advantage of the fact that there is room in the struct anyway, and that
it is already quite large and simply change the three bitfield members to
bools. This avoids writes to space_info->full having any effect on
---truncated---
CVSS Score
5.5
EPSS Score
0.0
Published
2025-12-24
In the Linux kernel, the following vulnerability has been resolved:
team: Move team device type change at the end of team_port_add
Attempting to add a port device that is already up will expectedly fail,
but not before modifying the team device header_ops.
In the case of the syzbot reproducer the gre0 device is
already in state UP when it attempts to add it as a
port device of team0, this fails but before that
header_ops->create of team0 is changed from eth_header to ipgre_header
in the call to team_dev_type_check_change.
Later when we end up in ipgre_header() struct ip_tunnel* points to nonsense
as the private data of the device still holds a struct team.
Example sequence of iproute2 commands to reproduce the hang/BUG():
ip link add dev team0 type team
ip link add dev gre0 type gre
ip link set dev gre0 up
ip link set dev gre0 master team0
ip link set dev team0 up
ping -I team0 1.1.1.1
Move team_dev_type_check_change down where all other checks have passed
as it changes the dev type with no way to restore it in case
one of the checks that follow it fail.
Also make sure to preserve the origial mtu assignment:
- If port_dev is not the same type as dev, dev takes mtu from port_dev
- If port_dev is the same type as dev, port_dev takes mtu from dev
This is done by adding a conditional before the call to dev_set_mtu
to prevent it from assigning port_dev->mtu = dev->mtu and instead
letting team_dev_type_check_change assign dev->mtu = port_dev->mtu.
The conditional is needed because the patch moves the call to
team_dev_type_check_change past dev_set_mtu.
Testing:
- team device driver in-tree selftests
- Add/remove various devices as slaves of team device
- syzbot
CVSS Score
5.5
EPSS Score
0.0
Published
2025-12-23