Linux: >> Linux Kernel >> 4.20.1 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
wifi: brcmfmac: Fix potential use-after-free issue when stopping watchdog task
Watchdog task might end between send_sig() and kthread_stop() calls, what
results in the use-after-free issue. Fix this by increasing watchdog task
reference count before calling send_sig() and dropping it by switching to
kthread_stop_put().
CVSS Score
7.8
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
RDMA/mlx4: Fix mis-use of RCU in mlx4_srq_event()
Sashiko points out the radix_tree itself is RCU safe, but nothing ever
frees the mlx4_srq struct with RCU, and it isn't even accessed within the
RCU critical section. It also will crash if an event is delivered before
the srq object is finished initializing.
Use the spinlock since it isn't easy to make RCU work, use
refcount_inc_not_zero() to protect against partially initialized objects,
and order the refcount_set() to be after the srq is fully initialized.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl
Just like in a previous problem in this driver, usblp_ctrl_msg() will
collapse the usb_control_msg() return value to 0/-errno, discarding the
actual number of bytes transferred.
Ideally that short command should be detected and error out, but many
printers are known to send "incorrect" responses back so we can't just
do that.
statusbuf is kmalloc(8) at probe time and never filled before the first
LPGETSTATUS ioctl.
usblp_read_status() requests 1 byte. If a malicious printer responds
with zero bytes, *statusbuf is one byte of stale kmalloc heap,
sign-extended into the local int status, which the LPGETSTATUS path then
copy_to_user()s directly to the ioctl caller.
Fix this all by just zapping out the memory buffer when allocated at
probe time. If a later call does a short read, the data will be
identical to what the device sent it the last time, so there is no
"leak" of information happening.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: fix uninit-value by validating catalog record size
Syzbot reported a KMSAN uninit-value issue in hfsplus_strcasecmp(). The
root cause is that hfs_brec_read() doesn't validate that the on-disk
record size matches the expected size for the record type being read.
When mounting a corrupted filesystem, hfs_brec_read() may read less data
than expected. For example, when reading a catalog thread record, the
debug output showed:
HFSPLUS_BREC_READ: rec_len=520, fd->entrylength=26
HFSPLUS_BREC_READ: WARNING - entrylength (26) < rec_len (520) - PARTIAL READ!
hfs_brec_read() only validates that entrylength is not greater than the
buffer size, but doesn't check if it's less than expected. It successfully
reads 26 bytes into a 520-byte structure and returns success, leaving 494
bytes uninitialized.
This uninitialized data in tmp.thread.nodeName then gets copied by
hfsplus_cat_build_key_uni() and used by hfsplus_strcasecmp(), triggering
the KMSAN warning when the uninitialized bytes are used as array indices
in case_fold().
Fix by introducing hfsplus_brec_read_cat() wrapper that:
1. Calls hfs_brec_read() to read the data
2. Validates the record size based on the type field:
- Fixed size for folder and file records
- Variable size for thread records (depends on string length)
3. Returns -EIO if size doesn't match expected
For thread records, check against HFSPLUS_MIN_THREAD_SZ before reading
nodeName.length to avoid reading uninitialized data at call sites that
don't zero-initialize the entry structure.
Also initialize the tmp variable in hfsplus_find_cat() as defensive
programming to ensure no uninitialized data even if validation is
bypassed.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
ALSA: pcm: oss: Fix data race at accessing runtime.oss.trigger
Currently the runtime.oss.trigger field may be accessed concurrently
without protection, which may lead to the data race. And, in this
case, it may lead to more severe problem because it's a bit field; as
writing the data, it may overwrite other bit fields as well, which
confuses the operation completely, as spotted by fuzzing.
Fix it by covering runtime.oss.trigger bit fled also with the existing
params_lock mutex in both snd_pcm_oss_get_trigger() and
snd_pcm_oss_poll().
CVSS Score
7.8
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix btrfs_ioctl_space_info() slot_count TOCTOU which can lead to info-leak
btrfs_ioctl_space_info() has a TOCTOU race between two passes over the
block group RAID type lists. The first pass counts entries to determine
the allocation size, then the second pass fills the buffer. The
groups_sem rwlock is released between passes, allowing concurrent block
group removal to reduce the entry count.
When the second pass fills fewer entries than the first pass counted,
copy_to_user() copies the full alloc_size bytes including trailing
uninitialized kmalloc bytes to userspace.
Fix by copying only total_spaces entries (the actually-filled count from
the second pass) instead of alloc_size bytes, and switch to kzalloc so
any future copy size mismatch cannot leak heap data.
CVSS Score
4.7
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix missing last_unlink_trans update when removing a directory
When removing a directory we are not updating its last_unlink_trans field,
which can result in incorrect fsync behaviour in case some one fsyncs the
directory after it was removed because it's holding a file descriptor on
it.
Example scenario:
mkdir /mnt/dir1
mkdir /mnt/dir1/dir2
mkdir /mnt/dir3
sync -f /mnt
# Do some change to the directory and fsync it.
chmod 700 /mnt/dir1
xfs_io -c fsync /mnt/dir1
# Move dir2 out of dir1 so that dir1 becomes empty.
mv /mnt/dir1/dir2 /mnt/dir3/
open fd on /mnt/dir1
call rmdir(2) on path "/mnt/dir1"
fsync fd
<trigger power failure>
When attempting to mount the filesystem, the log replay will fail with
an -EIO error and dmesg/syslog has the following:
[445771.626482] BTRFS info (device dm-0): first mount of filesystem 0368bbea-6c5e-44b5-b409-09abe496e650
[445771.626486] BTRFS info (device dm-0): using crc32c checksum algorithm
[445771.627912] BTRFS info (device dm-0): start tree-log replay
[445771.628335] page: refcount:2 mapcount:0 mapping:0000000061443ddc index:0x1d00 pfn:0x7072a5
[445771.629453] memcg:ffff89f400351b00
[445771.629892] aops:btree_aops [btrfs] ino:1
[445771.630737] flags: 0x17fffc00000402a(uptodate|lru|private|writeback|node=0|zone=2|lastcpupid=0x1ffff)
[445771.632359] raw: 017fffc00000402a fffff47284d950c8 fffff472907b7c08 ffff89f458e412b8
[445771.633713] raw: 0000000000001d00 ffff89f6c51d1a90 00000002ffffffff ffff89f400351b00
[445771.635029] page dumped because: eb page dump
[445771.635825] BTRFS critical (device dm-0): corrupt leaf: root=5 block=30408704 slot=10 ino=258, invalid nlink: has 2 expect no more than 1 for dir
[445771.638088] BTRFS info (device dm-0): leaf 30408704 gen 10 total ptrs 17 free space 14878 owner 5
[445771.638091] BTRFS info (device dm-0): refs 4 lock_owner 0 current 3581087
[445771.638094] item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160
[445771.638097] inode generation 3 transid 9 size 16 nbytes 16384
[445771.638098] block group 0 mode 40755 links 1 uid 0 gid 0
[445771.638100] rdev 0 sequence 2 flags 0x0
[445771.638102] atime 1775744884.0
[445771.660056] ctime 1775744885.645502983
[445771.660058] mtime 1775744885.645502983
[445771.660060] otime 1775744884.0
[445771.660062] item 1 key (256 INODE_REF 256) itemoff 16111 itemsize 12
[445771.660064] index 0 name_len 2
[445771.660066] item 2 key (256 DIR_ITEM 1843588421) itemoff 16077 itemsize 34
[445771.660068] location key (259 1 0) type 2
[445771.660070] transid 9 data_len 0 name_len 4
[445771.660075] item 3 key (256 DIR_ITEM 2363071922) itemoff 16043 itemsize 34
[445771.660076] location key (257 1 0) type 2
[445771.660077] transid 9 data_len 0 name_len 4
[445771.660078] item 4 key (256 DIR_INDEX 2) itemoff 16009 itemsize 34
[445771.660079] location key (257 1 0) type 2
[445771.660080] transid 9 data_len 0 name_len 4
[445771.660081] item 5 key (256 DIR_INDEX 3) itemoff 15975 itemsize 34
[445771.660082] location key (259 1 0) type 2
[445771.660083] transid 9 data_len 0 name_len 4
[445771.660084] item 6 key (257 INODE_ITEM 0) itemoff 15815 itemsize 160
[445771.660086] inode generation 9 transid 9 size 8 nbytes 0
[445771.660087] block group 0 mode 40777 links 1 uid 0 gid 0
[445771.660088] rdev 0 sequence 2 flags 0x0
[445771.660089] atime 1775744885.641174097
[445771.660090] ctime 1775744885.645502983
[445771.660091] mtime 1775744885.645502983
[445771.660105] otime 1775744885.641174097
[445771.660106] item 7 key (257 INODE_REF 256) itemoff 15801 itemsize 14
[445771.660107] index 2 name_len 4
[445771.660108] item 8 key (257 DIR_ITEM 2676584006) itemoff 15767 itemsize 34
[445771.660109] location key (2
---truncated---
CVSS Score
5.5
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
md/raid10: fix divide-by-zero in setup_geo() with zero far_copies
setup_geo() extracts near_copies (nc) and far_copies (fc) from the
user-provided layout parameter without checking for zero. When fc=0
with the "improved" far set layout selected, 'geo->far_set_size =
disks / fc' triggers a divide-by-zero.
Validate nc and fc immediately after extraction, returning -1 if
either is zero.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
wifi: b43legacy: enforce bounds check on firmware key index in RX path
Same fix as b43: the firmware-controlled key index in b43legacy_rx()
can exceed dev->max_nr_keys. The existing B43legacy_WARN_ON is
non-enforcing in production builds, allowing an out-of-bounds read of
dev->key[].
Make the check enforcing by dropping the frame for invalid indices.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-05-28
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Fix pin leak and publication ordering in __pkvm_init_vcpu()
Two bugs exist in the vCPU initialisation path:
1. If a check fails after hyp_pin_shared_mem() succeeds, the cleanup
path jumps to 'unlock' without calling unpin_host_vcpu() or
unpin_host_sve_state(), permanently leaking pin references on the
host vCPU and SVE state pages.
Extract a register_hyp_vcpu() helper that performs the checks and
the store. When register_hyp_vcpu() returns an error, call
unpin_host_vcpu() and unpin_host_sve_state() inline before falling
through to the existing 'unlock' label.
2. register_hyp_vcpu() publishes the new vCPU pointer into
'hyp_vm->vcpus[]' with a bare store, allowing a concurrent caller
of pkvm_load_hyp_vcpu() to observe a partially initialised vCPU
object.
Ensure the store uses smp_store_release() and the load uses
smp_load_acquire(). While 'vm_table_lock' currently serialises the
store and the load, these barriers ensure the reader sees the fully
initialised 'hyp_vcpu' object even if there were a lockless path or
if the lock's own ordering guarantees were insufficient for nested
object initialization.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-05-28