Linux: >> Linux Kernel >> 4.18.0-193.el8 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
btrfs: set BTRFS_ROOT_ORPHAN_CLEANUP during subvol create
We have recently observed a number of subvolumes with broken dentries.
ls-ing the parent dir looks like:
drwxrwxrwt 1 root root 16 Jan 23 16:49 .
drwxr-xr-x 1 root root 24 Jan 23 16:48 ..
d????????? ? ? ? ? ? broken_subvol
and similarly stat-ing the file fails.
In this state, deleting the subvol fails with ENOENT, but attempting to
create a new file or subvol over it errors out with EEXIST and even
aborts the fs. Which leaves us a bit stuck.
dmesg contains a single notable error message reading:
"could not do orphan cleanup -2"
2 is ENOENT and the error comes from the failure handling path of
btrfs_orphan_cleanup(), with the stack leading back up to
btrfs_lookup().
btrfs_lookup
btrfs_lookup_dentry
btrfs_orphan_cleanup // prints that message and returns -ENOENT
After some detailed inspection of the internal state, it became clear
that:
- there are no orphan items for the subvol
- the subvol is otherwise healthy looking, it is not half-deleted or
anything, there is no drop progress, etc.
- the subvol was created a while ago and does the meaningful first
btrfs_orphan_cleanup() call that sets BTRFS_ROOT_ORPHAN_CLEANUP much
later.
- after btrfs_orphan_cleanup() fails, btrfs_lookup_dentry() returns -ENOENT,
which results in a negative dentry for the subvolume via
d_splice_alias(NULL, dentry), leading to the observed behavior. The
bug can be mitigated by dropping the dentry cache, at which point we
can successfully delete the subvolume if we want.
i.e.,
btrfs_lookup()
btrfs_lookup_dentry()
if (!sb_rdonly(inode->vfs_inode)->vfs_inode)
btrfs_orphan_cleanup(sub_root)
test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)
btrfs_search_slot() // finds orphan item for inode N
...
prints "could not do orphan cleanup -2"
if (inode == ERR_PTR(-ENOENT))
inode = NULL;
return d_splice_alias(NULL, dentry) // NEGATIVE DENTRY for valid subvolume
btrfs_orphan_cleanup() does test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)
on the root when it runs, so it cannot run more than once on a given
root, so something else must run concurrently. However, the obvious
routes to deleting an orphan when nlinks goes to 0 should not be able to
run without first doing a lookup into the subvolume, which should run
btrfs_orphan_cleanup() and set the bit.
The final important observation is that create_subvol() calls
d_instantiate_new() but does not set BTRFS_ROOT_ORPHAN_CLEANUP, so if
the dentry cache gets dropped, the next lookup into the subvolume will
make a real call into btrfs_orphan_cleanup() for the first time. This
opens up the possibility of concurrently deleting the inode/orphan items
but most typical evict() paths will be holding a reference on the parent
dentry (child dentry holds parent->d_lockref.count via dget in
d_alloc(), released in __dentry_kill()) and prevent the parent from
being removed from the dentry cache.
The one exception is delayed iputs. Ordered extent creation calls
igrab() on the inode. If the file is unlinked and closed while those
refs are held, iput() in __dentry_kill() decrements i_count but does
not trigger eviction (i_count > 0). The child dentry is freed and the
subvol dentry's d_lockref.count drops to 0, making it evictable while
the inode is still alive.
Since there are two races (the race between writeback and unlink and
the race between lookup and delayed iputs), and there are too many moving
parts, the following three diagrams show the complete picture.
(Only the second and third are races)
Phase 1:
Create Subvol in dentry cache without BTRFS_ROOT_ORPHAN_CLEANUP set
btrfs_mksubvol()
lookup_one_len()
__lookup_slow()
d_alloc_parallel()
__d_alloc() // d_lockref.count = 1
create_subvol(dentry)
// doesn't touch the bit..
d_instantiate_new(dentry, inode) // dentry in cache with d_lockref.c
---truncated---
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
module: Fix kernel panic when a symbol st_shndx is out of bounds
The module loader doesn't check for bounds of the ELF section index in
simplify_symbols():
for (i = 1; i < symsec->sh_size / sizeof(Elf_Sym); i++) {
const char *name = info->strtab + sym[i].st_name;
switch (sym[i].st_shndx) {
case SHN_COMMON:
[...]
default:
/* Divert to percpu allocation if a percpu var. */
if (sym[i].st_shndx == info->index.pcpu)
secbase = (unsigned long)mod_percpu(mod);
else
/** HERE --> **/ secbase = info->sechdrs[sym[i].st_shndx].sh_addr;
sym[i].st_value += secbase;
break;
}
}
A symbol with an out-of-bounds st_shndx value, for example 0xffff
(known as SHN_XINDEX or SHN_HIRESERVE), may cause a kernel panic:
BUG: unable to handle page fault for address: ...
RIP: 0010:simplify_symbols+0x2b2/0x480
...
Kernel panic - not syncing: Fatal exception
This can happen when module ELF is legitimately using SHN_XINDEX or
when it is corrupted.
Add a bounds check in simplify_symbols() to validate that st_shndx is
within the valid range before using it.
This issue was discovered due to a bug in llvm-objcopy, see relevant
discussion for details [1].
[1] https://lore.kernel.org/linux-modules/20251224005752.201911-1-ihor.solodrai@linux.dev/
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix null-ptr-deref on l2cap_sock_ready_cb
Before using sk pointer, check if it is null.
Fix the following:
KASAN: null-ptr-deref in range [0x0000000000000260-0x0000000000000267]
CPU: 0 UID: 0 PID: 5985 Comm: kworker/0:5 Not tainted 7.0.0-rc4-00029-ga989fde763f4 #1 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-9.fc43 06/10/2025
Workqueue: events l2cap_info_timeout
RIP: 0010:kasan_byte_accessible+0x12/0x30
Code: 79 ff ff ff 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 40 d6 48 c1 ef 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 07 3c 08 0f 92 c0 c3 cc cce
veth0_macvtap: entered promiscuous mode
RSP: 0018:ffffc90006e0f808 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff89746018 RCX: 0000000080000001
RDX: 0000000000000000 RSI: ffffffff89746018 RDI: 000000000000004c
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff8aae3e70 R12: 0000000000000000
R13: 0000000000000260 R14: 0000000000000260 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8880983c2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005582615a5008 CR3: 000000007007e000 CR4: 0000000000752ef0
PKRU: 55555554
Call Trace:
<TASK>
__kasan_check_byte+0x12/0x40
lock_acquire+0x79/0x2e0
lock_sock_nested+0x48/0x100
? l2cap_sock_ready_cb+0x46/0x160
l2cap_sock_ready_cb+0x46/0x160
l2cap_conn_start+0x779/0xff0
? __pfx_l2cap_conn_start+0x10/0x10
? l2cap_info_timeout+0x60/0xa0
? __pfx___mutex_lock+0x10/0x10
l2cap_info_timeout+0x68/0xa0
? process_scheduled_works+0xa8d/0x18c0
process_scheduled_works+0xb6e/0x18c0
? __pfx_process_scheduled_works+0x10/0x10
? assign_work+0x3d5/0x5e0
worker_thread+0xa53/0xfc0
kthread+0x388/0x470
? __pfx_worker_thread+0x10/0x10
? __pfx_kthread+0x10/0x10
ret_from_fork+0x51e/0xb90
? __pfx_ret_from_fork+0x10/0x10
veth1_macvtap: entered promiscuous mode
? __switch_to+0xc7d/0x1450
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
batman_adv: batadv0: Interface activated: batadv_slave_0
batman_adv: batadv0: Interface activated: batadv_slave_1
netdevsim netdevsim7 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim7 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim7 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim7 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
RIP: 0010:kasan_byte_accessible+0x12/0x30
Code: 79 ff ff ff 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 40 d6 48 c1 ef 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 07 3c 08 0f 92 c0 c3 cc cce
ieee80211 phy39: Selected rate control algorithm 'minstrel_ht'
RSP: 0018:ffffc90006e0f808 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff89746018 RCX: 0000000080000001
RDX: 0000000000000000 RSI: ffffffff89746018 RDI: 000000000000004c
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff8aae3e70 R12: 0000000000000000
R13: 0000000000000260 R14: 0000000000000260 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8880983c2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7e16139e9c CR3: 000000000e74e000 CR4: 0000000000752ef0
PKRU: 55555554
Kernel panic - not syncing: Fatal exception
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Validate PDU length before reading SDU length in l2cap_ecred_data_rcv()
l2cap_ecred_data_rcv() reads the SDU length field from skb->data using
get_unaligned_le16() without first verifying that skb contains at least
L2CAP_SDULEN_SIZE (2) bytes. When skb->len is less than 2, this reads
past the valid data in the skb.
The ERTM reassembly path correctly calls pskb_may_pull() before reading
the SDU length (l2cap_reassemble_sdu, L2CAP_SAR_START case). Apply the
same validation to the Enhanced Credit Based Flow Control data path.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
af_key: validate families in pfkey_send_migrate()
syzbot was able to trigger a crash in skb_put() [1]
Issue is that pfkey_send_migrate() does not check old/new families,
and that set_ipsecrequest() @family argument was truncated,
thus possibly overfilling the skb.
Validate families early, do not wait set_ipsecrequest().
[1]
skbuff: skb_over_panic: text:ffffffff8a752120 len:392 put:16 head:ffff88802a4ad040 data:ffff88802a4ad040 tail:0x188 end:0x180 dev:<NULL>
kernel BUG at net/core/skbuff.c:214 !
Call Trace:
<TASK>
skb_over_panic net/core/skbuff.c:219 [inline]
skb_put+0x159/0x210 net/core/skbuff.c:2655
skb_put_zero include/linux/skbuff.h:2788 [inline]
set_ipsecrequest net/key/af_key.c:3532 [inline]
pfkey_send_migrate+0x1270/0x2e50 net/key/af_key.c:3636
km_migrate+0x155/0x260 net/xfrm/xfrm_state.c:2848
xfrm_migrate+0x2140/0x2450 net/xfrm/xfrm_policy.c:4705
xfrm_do_migrate+0x8ff/0xaa0 net/xfrm/xfrm_user.c:3150
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
net: fix fanout UAF in packet_release() via NETDEV_UP race
`packet_release()` has a race window where `NETDEV_UP` can re-register a
socket into a fanout group's `arr[]` array. The re-registration is not
cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout
array.
`packet_release()` does NOT zero `po->num` in its `bind_lock` section.
After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex`
still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`
that already found the socket in `sklist` can re-register the hook.
For fanout sockets, this re-registration calls `__fanout_link(sk, po)`
which adds the socket back into `f->arr[]` and increments `f->num_members`,
but does NOT increment `f->sk_ref`.
The fix sets `po->num` to zero in `packet_release` while `bind_lock` is
held to prevent NETDEV_UP from linking, preventing the race window.
This bug was found following an additional audit with Claude Code based
on CVE-2025-38617.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
nfc: nci: fix circular locking dependency in nci_close_device
nci_close_device() flushes rx_wq and tx_wq while holding req_lock.
This causes a circular locking dependency because nci_rx_work()
running on rx_wq can end up taking req_lock too:
nci_rx_work -> nci_rx_data_packet -> nci_data_exchange_complete
-> __sk_destruct -> rawsock_destruct -> nfc_deactivate_target
-> nci_deactivate_target -> nci_request -> mutex_lock(&ndev->req_lock)
Move the flush of rx_wq after req_lock has been released.
This should safe (I think) because NCI_UP has already been cleared
and the transport is closed, so the work will see it and return
-ENETDOWN.
NIPA has been hitting this running the nci selftest with a debug
kernel on roughly 4% of the runs.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: btintel: serialize btintel_hw_error() with hci_req_sync_lock
btintel_hw_error() issues two __hci_cmd_sync() calls (HCI_OP_RESET
and Intel exception-info retrieval) without holding
hci_req_sync_lock(). This lets it race against
hci_dev_do_close() -> btintel_shutdown_combined(), which also runs
__hci_cmd_sync() under the same lock. When both paths manipulate
hdev->req_status/req_rsp concurrently, the close path may free the
response skb first, and the still-running hw_error path hits a
slab-use-after-free in kfree_skb().
Wrap the whole recovery sequence in hci_req_sync_lock/unlock so it
is serialized with every other synchronous HCI command issuer.
Below is the data race report and the kasan report:
BUG: data-race in __hci_cmd_sync_sk / btintel_shutdown_combined
read of hdev->req_rsp at net/bluetooth/hci_sync.c:199
by task kworker/u17:1/83:
__hci_cmd_sync_sk+0x12f2/0x1c30 net/bluetooth/hci_sync.c:200
__hci_cmd_sync+0x55/0x80 net/bluetooth/hci_sync.c:223
btintel_hw_error+0x114/0x670 drivers/bluetooth/btintel.c:254
hci_error_reset+0x348/0xa30 net/bluetooth/hci_core.c:1030
write/free by task ioctl/22580:
btintel_shutdown_combined+0xd0/0x360
drivers/bluetooth/btintel.c:3648
hci_dev_close_sync+0x9ae/0x2c10 net/bluetooth/hci_sync.c:5246
hci_dev_do_close+0x232/0x460 net/bluetooth/hci_core.c:526
BUG: KASAN: slab-use-after-free in
sk_skb_reason_drop+0x43/0x380 net/core/skbuff.c:1202
Read of size 4 at addr ffff888144a738dc
by task kworker/u17:1/83:
__hci_cmd_sync_sk+0x12f2/0x1c30 net/bluetooth/hci_sync.c:200
__hci_cmd_sync+0x55/0x80 net/bluetooth/hci_sync.c:223
btintel_hw_error+0x186/0x670 drivers/bluetooth/btintel.c:260
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
team: fix header_ops type confusion with non-Ethernet ports
Similar to commit 950803f72547 ("bonding: fix type confusion in
bond_setup_by_slave()") team has the same class of header_ops type
confusion.
For non-Ethernet ports, team_setup_by_port() copies port_dev->header_ops
directly. When the team device later calls dev_hard_header() or
dev_parse_header(), these callbacks can run with the team net_device
instead of the real lower device, so netdev_priv(dev) is interpreted as
the wrong private type and can crash.
The syzbot report shows a crash in bond_header_create(), but the root
cause is in team: the topology is gre -> bond -> team, and team calls
the inherited header_ops with its own net_device instead of the lower
device, so bond_header_create() receives a team device and interprets
netdev_priv() as bonding private data, causing a type confusion crash.
Fix this by introducing team header_ops wrappers for create/parse,
selecting a team port under RCU, and calling the lower device callbacks
with port->dev, so each callback always sees the correct net_device
context.
Also pass the selected lower device to the lower parse callback, so
recursion is bounded in stacked non-Ethernet topologies and parse
callbacks always run with the correct device context.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
udp: Fix wildcard bind conflict check when using hash2
When binding a udp_sock to a local address and port, UDP uses
two hashes (udptable->hash and udptable->hash2) for collision
detection. The current code switches to "hash2" when
hslot->count > 10.
"hash2" is keyed by local address and local port.
"hash" is keyed by local port only.
The issue can be shown in the following bind sequence (pseudo code):
bind(fd1, "[fd00::1]:8888")
bind(fd2, "[fd00::2]:8888")
bind(fd3, "[fd00::3]:8888")
bind(fd4, "[fd00::4]:8888")
bind(fd5, "[fd00::5]:8888")
bind(fd6, "[fd00::6]:8888")
bind(fd7, "[fd00::7]:8888")
bind(fd8, "[fd00::8]:8888")
bind(fd9, "[fd00::9]:8888")
bind(fd10, "[fd00::10]:8888")
/* Correctly return -EADDRINUSE because "hash" is used
* instead of "hash2". udp_lib_lport_inuse() detects the
* conflict.
*/
bind(fail_fd, "[::]:8888")
/* After one more socket is bound to "[fd00::11]:8888",
* hslot->count exceeds 10 and "hash2" is used instead.
*/
bind(fd11, "[fd00::11]:8888")
bind(fail_fd, "[::]:8888") /* succeeds unexpectedly */
The same issue applies to the IPv4 wildcard address "0.0.0.0"
and the IPv4-mapped wildcard address "::ffff:0.0.0.0". For
example, if there are existing sockets bound to
"192.168.1.[1-11]:8888", then binding "0.0.0.0:8888" or
"[::ffff:0.0.0.0]:8888" can also miss the conflict when
hslot->count > 10.
TCP inet_csk_get_port() already has the correct check in
inet_use_bhash2_on_bind(). Rename it to
inet_use_hash2_on_bind() and move it to inet_hashtables.h
so udp.c can reuse it in this fix.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22