Linux: >> Linux Kernel >> 4.14.63 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
btrfs: only release the dirty pages io tree after successful writes
[WARNING]
With extra warning on dirty extent buffers at umount (aka, the next
patch in the series), test case generic/388 can trigger the following
warning about dirty extent buffers at unmount time:
BTRFS critical (device dm-2 state E): emergency shutdown
BTRFS error (device dm-2 state E): error while writing out transaction: -30
BTRFS warning (device dm-2 state E): Skipping commit of aborted transaction.
BTRFS error (device dm-2 state EA): Transaction 9 aborted (error -30)
BTRFS: error (device dm-2 state EA) in cleanup_transaction:2068: errno=-30 Readonly filesystem
BTRFS info (device dm-2 state EA): forced readonly
BTRFS info (device dm-2 state EA): last unmount of filesystem 4fbf2e15-f941-49a0-bc7c-716315d2777c
------------[ cut here ]------------
WARNING: disk-io.c:3311 at invalidate_and_check_btree_folios+0xfd/0x1ca [btrfs], CPU#8: umount/914368
CPU: 8 UID: 0 PID: 914368 Comm: umount Tainted: G OE 7.1.0-rc1-custom+ #372 PREEMPT(full) 2de38db8d1deae71fde295430a0ff3ab98ccf596
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022
RIP: 0010:invalidate_and_check_btree_folios+0xfd/0x1ca [btrfs]
Call Trace:
<TASK>
close_ctree+0x52e/0x574 [btrfs d2f0b1cd330d1287e7a9919d112eadfc0e914efd]
generic_shutdown_super+0x89/0x1a0
kill_anon_super+0x16/0x40
btrfs_kill_super+0x16/0x20 [btrfs d2f0b1cd330d1287e7a9919d112eadfc0e914efd]
deactivate_locked_super+0x2d/0xb0
cleanup_mnt+0xdc/0x140
task_work_run+0x5a/0xa0
exit_to_user_mode_loop+0x123/0x4b0
do_syscall_64+0x243/0x7c0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
---[ end trace 0000000000000000 ]---
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30539776 owner 9 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30621696 owner 257 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30638080 owner 258 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30654464 owner 7 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30703616 owner 2 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30720000 owner 10 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30736384 owner 4 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30752768 owner 11 gen 9 refs 2 flags 0x7
I'm using a stripped down version, which seems to trigger the warning
more reliably:
_fsstress_pid=""
workload()
{
dmesg -C
mkfs.btrfs -f -K $dev > /dev/null
echo 1 > /sys/kernel/debug/clear_warn_once
mount $dev $mnt
$fsstress -w -n 1024 -p 4 -d $mnt &
_fsstress_pid=$!
sleep 0
$godown $mnt
pkill --echo -PIPE fsstress > /dev/null
wait $_fsstress_pid
unset _fsstress_pid
umount $mnt
if dmesg | grep -q "WARNING"; then
fail
fi
}
for (( i = 0; i < $runtime; i++ )); do
echo "=== $i/$runtime ==="
workload
done
[CAUSE]
Inside btrfs_write_and_wait_transaction(), we first try to write all
dirty ebs, then wait for them to finish.
After that we call btrfs_extent_io_tree_release() to free all
extent states from dirty_pages io tree.
However if we hit an error from btrfs_write_marked_extent(), then we
still call btrfs_extent_io_tree_release() to clear that dirty_pages io
tree, which may contain dirty records that we haven't yet submitted.
Furthermore, the later transaction cleanup path will utilize that
dirty_pages io tree to properly cleanup those dirty ebs, but since it's
already empty, no dirty ebs are properly cleaned up, thus will later
trigger the warnings inside invalidate_btree_folios().
---truncated---
CVSS Score
7.5
EPSS Score
0.004
Published
2026-06-26
In the Linux kernel, the following vulnerability has been resolved:
ipvs: clear the svc scheduler ptr early on edit
ip_vs_edit_service() while unbinding the old scheduler clears
the svc->scheduler ptr after the scheduler module initiates
RCU callbacks. This can cause packets to use the old
scheduler at the time when svc->sched_data is already freed
after RCU grace period.
Fix it by clearing the ptr early in ip_vs_unbind_scheduler(),
before the done_service method schedules any RCU callbacks.
Also, if the new scheduler fails to initialize when replacing
the old scheduler, try to restore the old scheduler while still
returning the error code.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
ipv6: mcast: Fix use-after-free when processing MLD queries
When processing an MLD query, a pointer to the multicast group address
is retrieved when initially parsing the packet. This pointer is later
dereferenced without being reloaded despite the fact that the skb header
might have been reallocated following the pskb_may_pull() calls, leading
to a use-after-free [1].
Fix by copying the multicast group address when the packet is initially
parsed.
[1]
BUG: KASAN: slab-use-after-free in __mld_query_work (net/ipv6/mcast.c:1512)
Read of size 8 at addr ffff8881154b8e90 by task kworker/4:1/118
Workqueue: mld mld_query_work
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
print_address_description.constprop.0 (mm/kasan/report.c:378)
print_report (mm/kasan/report.c:482)
kasan_report (mm/kasan/report.c:595)
__mld_query_work (net/ipv6/mcast.c:1512)
mld_query_work (net/ipv6/mcast.c:1563)
process_one_work (kernel/workqueue.c:3314)
worker_thread (kernel/workqueue.c:3397 kernel/workqueue.c:3478)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
</TASK>
[...]
Freed by task 118:
kasan_save_stack (mm/kasan/common.c:57)
kasan_save_track (mm/kasan/common.c:78)
kasan_save_free_info (mm/kasan/generic.c:584)
__kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)
kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6251 mm/slub.c:6566)
pskb_expand_head (net/core/skbuff.c:2335)
__pskb_pull_tail (net/core/skbuff.c:2878 (discriminator 4))
__mld_query_work (net/ipv6/mcast.c:1495 (discriminator 1))
mld_query_work (net/ipv6/mcast.c:1563)
process_one_work (kernel/workqueue.c:3314)
worker_thread (kernel/workqueue.c:3397 kernel/workqueue.c:3478)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
CVSS Score
8.8
EPSS Score
0.003
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()
pppol2tp_ioctl() read sock->sk->sk_user_data directly without any
locks or reference counting. If a controllable sleep was induced during
copy_from_user() (e.g. via a userfaultfd page fault sleep), a concurrent
socket close could trigger pppol2tp_session_close() asynchronously. This
frees the l2tp_session structure via the l2tp_session_del_work workqueue.
Upon resuming, the ioctl thread dereferences the stale session pointer,
resulting in a Use-After-Free (UAF).
Fix this by securely fetching the session reference using the RCU-safe,
refcounted helper pppol2tp_sock_to_session(sk) on entry. This locks the
session's refcount across the sleep. We structured the function to exit
via standard err breaks, guaranteeing that l2tp_session_put() is cleanly
called on all return paths to drop the reference.
To preserve existing behavior we validate the session and its magic
signature only for the specific L2TP commands that require it. This
ensures that generic/unknown ioctls called on an unconnected socket
still return -ENOIOCTLCMD and correctly fall back to generic handlers
(e.g. in sock_do_ioctl()).
CVSS Score
7.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
6lowpan: fix off-by-one in multicast context address compression
The second memcpy in lowpan_iphc_mcast_ctx_addr_compress() uses
&data[1] as destination and &ipaddr->s6_addr[11] as source, but
both should be offset by one: &data[2] and &ipaddr->s6_addr[12]
respectively.
This off-by-one has two consequences:
1. data[1] is overwritten with s6_addr[11], corrupting the RIID
field in the compressed multicast address
2. data[5] is never written, so uninitialized kernel stack memory
is transmitted over the network via lowpan_push_hc_data(),
leaking kernel stack contents
The correct inline data layout must match what the decompression
function lowpan_uncompress_multicast_ctx_daddr() expects:
data[0..1] = s6_addr[1..2] (flags/scope + RIID)
data[2..5] = s6_addr[12..15] (group ID)
Also zero-initialize the data array as a defensive measure against
similar bugs in the future.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_api: use RCU with deferred freeing for action lifecycle
When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
race with an associated action.
Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:
0: mutex_lock() <-- holds the idr lock
0: rcu_read_lock()
0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)
0: mutex_unlock() <-- releases the idr lock
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index) <-- Action removed from IDR
1: mutex_unlock() <-- mutex released allowing us to delete the action
1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory
This patch fixes the race condition between NEWTFILTER and DELFILTER by
adding struct rcu_head to tc_action used in the deferral and introducing a
call_rcu() in the delete path to defer the final kfree().
Note: this is a revert of commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu")
but also modernization/simplification to directly use kfree_rcu().
Let's illustrate the new restored code path:
0: rcu_read_lock()
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index)
1: mutex_unlock()
1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period
0: p = idr_find(idr, index)
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0
1: rcu_read_unlock() <-- release so freeing can run after grace period
After CPU1 calls idr_remove(), the object is no longer reachable through the IDR.
CPU0's subsequent idr_find() will return NULL, and even if it still held a
stale pointer, the immediate kfree() is now deferred until after the RCU grace
period, so no UAF can occur.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_ct: bail out on template ct in get eval
I noticed this issue while looking at a historic syzbot report [1].
A rule like the one below is enough to trigger the bug:
table ip t {
chain pre {
type filter hook prerouting priority raw;
ct zone set 1
ct original saddr 1.2.3.4 accept
}
}
The first expression attaches a per-cpu template ct via
nft_ct_set_zone_eval() (nf_ct_tmpl_alloc -> kzalloc, tuple is all
zero, nf_ct_l3num(ct) == 0). The next expression then calls
nft_ct_get_eval() on the same skb, treats the template as a real ct
and hits the 16-byte memcpy path. With dreg at NFT_REG32_15 this
overflows past struct nft_regs on the kernel stack; with smaller
dreg values it silently clobbers adjacent registers.
Reject template ct at the eval entry and in nft_ct_get_fast_eval(),
mirroring the check nft_ct_set_eval() already has. Additionally,
bound the address copy in NFT_CT_SRC / NFT_CT_DST by priv->len
instead of by nf_ct_l3num(ct): nf_ct_get_tuple() zeroes the tuple
before pkt_to_tuple() fills in only the protocol-relevant leading
bytes, so the trailing bytes of tuple->{src,dst}.u3.all are
well-defined zero. priv->len is validated at rule load, so the
copy size is now bounded by the destination register rather than
by an untrusted field on the conntrack.
[1]: https://syzkaller.appspot.com/bug?id=389cf09cb72926114fce90dc85a2c3231dcb647c
CVSS Score
7.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: bnep: reject short frames before parsing
A BNEP peer can send a short BNEP SDU. bnep_rx_frame() reads the
packet type byte immediately and, for control packets, reads the control
opcode and setup UUID-size byte before proving that those bytes are
present. bnep_rx_control() also dereferences the control opcode without
rejecting an empty control payload.
Use skb_pull_data() for the fixed fields in bnep_rx_frame() so a NULL
return gates each dereference. Split the control handler so the frame
path can pass an opcode that has already been pulled, and keep the
byte-buffer wrapper for extension control payloads.
For BNEP_SETUP_CONN_REQ, name the UUID-size byte before pulling the
setup payload. struct bnep_setup_conn_req carries destination and source
service UUIDs after that byte, each uuid_size bytes, so the parser now
documents that tuple explicitly instead of leaving the pull length as an
opaque multiplication.
Validation reproduced this kernel report:
KASAN slab-out-of-bounds in bnep_rx_frame.isra.0+0x130c/0x1790
The buggy address belongs to the object at ffff88800c0f7908 which belongs
to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes to the right of allocated 1-byte
region [ffff88800c0f7908, ffff88800c0f7909)
Read of size 1
Call trace:
dump_stack_lvl+0xb3/0x140 (?:?)
print_address_description+0x57/0x3a0 (?:?)
bnep_rx_frame+0x130c/0x1790 (net/bluetooth/bnep/core.c:306)
print_report+0xb9/0x2b0 (?:?)
__virt_addr_valid+0x1ba/0x3a0 (?:?)
srso_alias_return_thunk+0x5/0xfbef5 (?:?)
kasan_addr_to_slab+0x21/0x60 (?:?)
kasan_report+0xe0/0x110 (?:?)
process_one_work+0xfce/0x17e0 (kernel/workqueue.c:3200)
worker_thread+0x65c/0xe40 (?:?)
__kthread_parkme+0x184/0x230 (?:?)
kthread+0x35e/0x470 (?:?)
_raw_spin_unlock_irq+0x28/0x50 (?:?)
ret_from_fork+0x586/0x870 (?:?)
__switch_to+0x74f/0xdc0 (?:?)
ret_from_fork_asm+0x1a/0x30 (?:?)
CVSS Score
7.1
EPSS Score
0.003
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: RFCOMM: validate skb length in MCC handlers
The RFCOMM MCC handlers cast skb->data to protocol-specific structs
without validating skb->len first. A malicious remote device can send
truncated MCC frames and trigger out-of-bounds reads in these handlers.
Fix this by using skb_pull_data() to validate and access the required
data before dereferencing it.
rfcomm_recv_rpn() requires special handling since ETSI TS 07.10 allows
1-byte RPN requests. Handle this by validating only the DLCI byte first,
and validating the full struct only when len > 1.
CVSS Score
8.1
EPSS Score
0.003
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: MGMT: validate advertising TLV before type checks
tlv_data_is_valid() reads each advertising data field length from
data[i], then inspects data[i + 1] for managed EIR types before
checking that the current field still fits inside the supplied buffer.
A malformed field whose length byte is the last byte of the buffer can
therefore make the parser read one byte past the advertising data.
KASAN reported the following when a malformed MGMT_OP_ADD_ADVERTISING
request reached that path:
BUG: KASAN: vmalloc-out-of-bounds in tlv_data_is_valid()
Read of size 1
Call trace:
tlv_data_is_valid()
add_advertising()
hci_mgmt_cmd()
hci_sock_sendmsg()
Move the existing element-length check before any type-octet inspection
so each non-empty element is proven to contain its type byte before the
parser looks at data[i + 1].
CVSS Score
7.1
EPSS Score
0.002
Published
2026-06-25