Linux: >> Linux Kernel >> 4.20.8 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: cancel pending_rx_work before taking conn->lock
l2cap_conn_del() takes conn->lock and then calls cancel_work_sync() for
pending_rx_work. process_pending_rx() takes the same mutex, so teardown
can deadlock against the worker it is flushing.
This issue was found by our static analysis tool and then manually
reviewed against the current tree.
The grounded PoC kept the l2cap_conn_ready() -> queue_work(...,
&conn->pending_rx_work) submit path, the l2cap_conn_del() ->
cancel_work_sync(&conn->pending_rx_work) teardown path, and the
process_pending_rx() -> mutex_lock(&conn->lock) worker edge. Lockdep
WARNING: possible circular locking dependency detected
process_pending_rx+0x21/0x2a [vuln_msv]
l2cap_conn_del.constprop.0+0x3f/0x4e [vuln_msv]
*** DEADLOCK ***
Cancel pending_rx_work before taking conn->lock, matching the existing
lock-before-drain ordering used for the two delayed works in the same
teardown path. The pending_rx queue is still purged after the work has
been cancelled and conn->lock has been acquired.
CVSS Score
8.8
EPSS Score
0.003
Published
2026-07-20
In the Linux kernel, the following vulnerability has been resolved:
xfs: fail recovery on a committed log item with no regions
If the first op of a transaction is a bare transaction header
(len == sizeof(struct xfs_trans_header)), xlog_recover_add_to_trans()
adds an item but no region, leaving it on r_itemq with ri_cnt == 0 and
ri_buf == NULL.
The header can be split across op records, so later ops may still add
regions; the item is only invalid if the transaction commits with none.
The runtime commit path never emits such a transaction, so this only
happens on a crafted log. It came from an AI-assisted code audit of the
recovery parser.
xlog_recover_reorder_trans() calls ITEM_TYPE() on the item, which reads
*(unsigned short *)item->ri_buf[0].iov_base and faults on the NULL
ri_buf. Reject it there, before the commit handlers that also read
ri_buf[0].
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
RIP: 0010:xlog_recover_reorder_trans (fs/xfs/xfs_log_recover.c:1836)
xlog_recover_commit_trans (fs/xfs/xfs_log_recover.c:2043)
xlog_recover_process_data (fs/xfs/xfs_log_recover.c:2501)
xlog_do_recovery_pass (fs/xfs/xfs_log_recover.c:3244)
xlog_recover (fs/xfs/xfs_log_recover.c:3493)
xfs_log_mount (fs/xfs/xfs_log.c:618)
xfs_mountfs (fs/xfs/xfs_mount.c:1034)
xfs_fs_fill_super (fs/xfs/xfs_super.c:1938)
vfs_get_tree (fs/super.c:1695)
path_mount (fs/namespace.c:4161)
__x64_sys_mount (fs/namespace.c:4367)
CVSS Score
5.5
EPSS Score
0.002
Published
2026-07-20
In the Linux kernel, the following vulnerability has been resolved:
net: qualcomm: rmnet: fix endpoint use-after-free in rmnet_dellink()
rmnet_dellink() removes the endpoint from the hash table with
hlist_del_init_rcu() and then immediately frees it with kfree(). However,
RCU readers on the receive path (rmnet_rx_handler ->
__rmnet_map_ingress_handler) may still hold a reference to the endpoint and
dereference ep->egress_dev after the memory has been freed. The endpoint is
a kmalloc-32 object, and the stale read at offset 8 corresponds to the
egress_dev pointer.
BUG: unable to handle page fault for address: ffffffffde942eef
Oops: 0002 [#1] SMP NOPTI
CPU: 1 UID: 0 PID: 137 Comm: poc_write Not tainted 7.0.0+ #4 PREEMPTLAZY
RIP: 0010:rmnet_vnd_rx_fixup (rmnet_vnd.c:27)
Call Trace:
<TASK>
__rmnet_map_ingress_handler (rmnet_handlers.c:48 rmnet_handlers.c:101)
rmnet_rx_handler (rmnet_handlers.c:129 rmnet_handlers.c:235)
__netif_receive_skb_core.constprop.0 (net/core/dev.c:6096)
__netif_receive_skb_one_core (net/core/dev.c:6208)
netif_receive_skb (net/core/dev.c:6467)
tun_get_user (drivers/net/tun.c:1955)
tun_chr_write_iter (drivers/net/tun.c:2003)
vfs_write (fs/read_write.c:688)
ksys_write (fs/read_write.c:740)
</TASK>
Add an rcu_head field to struct rmnet_endpoint and replace kfree() with
kfree_rcu() so the endpoint memory remains valid through the RCU grace
period. Also remove the rmnet_vnd_dellink() call and inline only the
nr_rmnet_devs decrement, since rmnet_vnd_dellink() would set
ep->egress_dev to NULL during the grace period, creating a data race
with lockless readers.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-07-20
In the Linux kernel, the following vulnerability has been resolved:
netfilter: ipset: fix race between dump and ip_set_list resize
The release path of ip_set_dump_do() and ip_set_dump_done() read
inst->ip_set_list via ip_set_ref_netlink(), a plain rcu_dereference_raw()
of the array pointer. These run from netlink_recvmsg() without the nfnl
mutex and without an RCU read-side critical section.
A concurrent ip_set_create() can grow the array: it publishes the new
array, calls synchronize_net() and then kvfree()s the old one. Since the
dump paths read the array outside any RCU reader, synchronize_net() does
not wait for them and the old array can be freed while they still index
into it, causing a use-after-free.
The dumped set itself stays pinned via set->ref_netlink, so only the
array load needs protecting. Take rcu_read_lock() around it, matching
ip_set_get_byname() and __ip_set_put_byindex().
BUG: KASAN: slab-use-after-free in ip_set_dump_do (net/netfilter/ipset/ip_set_core.c:1697)
Read of size 8 at addr ffff88800b5c4018 by task exploit/150
Call Trace:
...
kasan_report (mm/kasan/report.c:595)
ip_set_dump_do (net/netfilter/ipset/ip_set_core.c:1697)
netlink_dump (net/netlink/af_netlink.c:2325)
netlink_recvmsg (net/netlink/af_netlink.c:1976)
sock_recvmsg (net/socket.c:1159)
__sys_recvfrom (net/socket.c:2315)
...
Oops: general protection fault, probably for non-canonical address ... KASAN NOPTI
KASAN: maybe wild-memory-access in range [0x02d6...d0-0x02d6...d7]
RIP: 0010:ip_set_dump_do (net/netfilter/ipset/ip_set_core.c:1698)
Kernel panic - not syncing: Fatal exception
CVSS Score
7.8
EPSS Score
0.001
Published
2026-07-20
In the Linux kernel, the following vulnerability has been resolved:
sysfs: don't remove existing directory on update failure
When sysfs_update_group() is called for a named group and create_files()
fails (e.g. -ENOMEM), internal_create_group() calls kernfs_remove(kn) on
the group directory. In the update path, kn was obtained via
kernfs_find_and_get() and refers to a directory that already existed
before this call. Removing it silently destroys a sysfs group that the
caller did not create.
Only remove the directory if we created it ourselves. On update failure
the directory remains as it is left empty by remove_files() inside
create_files(), but can be repopulated by a retry.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
af_unix: Fix UAF read of tail->len in unix_stream_data_wait()
unix_stream_data_wait() does skb_peek_tail(&sk->sk_receive_queue) without
holding any lock that prevents SKBs on that queue from being dequeued and
freed.
This has been the case since commit 79f632c71bea ("unix/stream: fix
peeking with an offset larger than data in queue").
The first consequence of this is that the pointer comparison
`tail != last` can be false even if `last` semantically refers to an
already-freed SKB while `tail` is a new SKB allocated at the same address;
which can cause unix_stream_data_wait() to wrongly keep blocking after new
data has arrived, but only in a weird scenario where a peeking recv() and
a normal recv() on the same socket are racing, which is probably not a
real problem.
But since commit 2b514574f7e8 ("net: af_unix: implement splice for stream
af_unix sockets"), `tail` is actually dereferenced, which can cause UAF in
the following race scenario (where test_setup() runs single-threaded,
and afterwards, test_thread1() and test_thread2() run concurrently in
two threads:
```
static int socks[2];
void test_setup(void) {
socketpair(AF_UNIX, SOCK_STREAM, 0, socks);
send(socks[1], "A", 1, 0);
int peekoff = 1;
setsockopt(socks[0], SOL_SOCKET, SO_PEEK_OFF, &peekoff, sizeof(peekoff));
}
void test_thread1(void) {
char dummy;
recv(socks[0], &dummy, 1, MSG_PEEK);
}
void test_thread2(void) {
char dummy;
recv(socks[0], &dummy, 1, 0);
shutdown(socks[1], SHUT_WR);
}
```
when racing like this:
```
thread1 thread2
unix_stream_read_generic
mutex_lock(&u->iolock)
skb_peek(&sk->sk_receive_queue)
skb_peek_next(skb, &sk->sk_receive_queue)
mutex_unlock(&u->iolock)
unix_stream_read_generic
unix_state_lock(sk)
skb_peek(&sk->sk_receive_queue)
unix_state_unlock(sk)
unix_stream_data_wait
unix_state_lock(sk)
tail = skb_peek_tail(&sk->sk_receive_queue)
spin_lock(&sk->sk_receive_queue.lock)
__skb_unlink(skb, &sk->sk_receive_queue)
spin_unlock(&sk->sk_receive_queue.lock)
consume_skb(skb) [frees the SKB]
`tail != last`: false
`tail`: true
`tail->len != last_len` ***UAF***
```
Fix the UAF by removing the read of tail->len; checking tail->len would
only make sense if SKBs in the receive queue of a UNIX socket could grow,
which can no longer happen.
Kuniyuki explained:
> When commit 869e7c62486e ("net: af_unix: implement stream sendpage
> support") added sendpage() support, data could be appended to the last
> skb in the receiver's queue.
>
> That's why we needed to check if the length of the last skb was changed
> while waiting for new data in unix_stream_data_wait().
>
> However, commit a0dbf5f818f9 ("af_unix: Support MSG_SPLICE_PAGES") and
> commit 57d44a354a43 ("unix: Convert unix_stream_sendpage() to use
> MSG_SPLICE_PAGES") refactored sendmsg(), and now data is always added
> to a new skb.
That means this fix is not suitable for kernels before 6.5.
CVSS Score
8.8
EPSS Score
0.001
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
rbd: eliminate a race in lock_dwork draining on unmap
Given how rbd_lock_add_request() and rbd_img_exclusive_lock() are
written, lock_dwork may be (re)queued more than it's actually needed:
for example in case a new I/O request comes in while we are in the
middle of rbd_acquire_lock() on behalf of another I/O request. This is
expected and with rbd_release_lock() preemptively canceling lock_dwork
is benign under normal operation.
A more problematic example is maybe_kick_acquire():
if (have_requests || delayed_work_pending(&rbd_dev->lock_dwork)) {
dout("%s rbd_dev %p kicking lock_dwork\n", __func__, rbd_dev);
mod_delayed_work(rbd_dev->task_wq, &rbd_dev->lock_dwork, 0);
}
It's not unrealistic for lock_dwork to get canceled right after
delayed_work_pending() returns true and for mod_delayed_work() to
requeue it right there anyway. This is a classic TOCTOU race.
When it comes to unmapping the image, there is an implicit assumption
of no self-initiated exclusive lock activity past the point of return
from rbd_dev_image_unlock() which unlocks the lock if it happens to be
held. This unlock is assumed to be final and lock_dwork (as well as
all other exclusive lock tasks, really) isn't expected to get queued
again. However, lock_dwork is canceled only in cancel_tasks_sync()
(i.e. later in the unmap sequence) and on top of that the cancellation
can get in effect nullified by maybe_kick_acquire(). This may result
in rbd_acquire_lock() executing after rbd_dev_device_release() and
rbd_dev_image_release() run and free and/or reset a bunch of things.
One of the possible failure modes then is a violated
rbd_assert(rbd_image_format_valid(rbd_dev->image_format));
in rbd_dev_header_info() which is called via rbd_dev_refresh() from
rbd_post_acquire_action().
Redo exclusive lock task draining to provide saner semantics and try
to meet the assumptions around rbd_dev_image_unlock().
CVSS Score
7.8
EPSS Score
0.001
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
ixgbevf: fix use-after-free in VEPA multicast source pruning
ixgbevf_clean_rx_irq() prunes frames whose source MAC matches the VF's
own address (VEPA multicast workaround) by freeing the skb and
continuing to the next descriptor:
dev_kfree_skb_irq(skb);
continue;
The skb pointer is declared outside the while loop and persists across
iterations. Because the continue skips the "skb = NULL" reset at the
bottom of the loop, the next iteration enters the "else if (skb)" path
and calls ixgbevf_add_rx_frag() on the freed skb, dereferencing
skb_shinfo(skb)->nr_frags - a use-after-free in NAPI softirq context.
The sibling driver iavf already handles this correctly by nulling the
pointer before continuing. Apply the same pattern here.
I do not have ixgbevf hardware; the bug was found by static analysis
(scan_drop_continue_loops.py + semgrep drop_continue_in_loop, multi-tool
corroboration with the highest score in the scan). The UAF was confirmed
under KASAN by loading a test module that reproduces the exact code
pattern (alloc skb, kfree_skb, then read skb_shinfo(skb)->nr_frags):
BUG: KASAN: slab-use-after-free in ixgbevf_uaf_test_init+0x100/0x1000
Read of size 8 at addr 000000006163ae78 by task insmod/30
freed 208-byte region [000000006163adc0, 000000006163ae90)
QEMU emulates igb (82576) but not ixgbe (82599), and the igbvf VF
driver does not include the VEPA source pruning path, so a full
end-to-end reproduction with emulated hardware was not possible.
CVSS Score
9.8
EPSS Score
0.005
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
vsock/vmci: fix UAF when peer resets connection during handshake
vmci_transport_recv_connecting_server() returned err = 0 for a peer
RST in its default switch arm:
err = pkt->type == VMCI_TRANSPORT_PACKET_TYPE_RST ? 0 : -EINVAL;
That made vmci_transport_recv_listen() skip vsock_remove_pending(),
leaving the pending socket on the listener's pending_links with
sk_state = TCP_CLOSE while destroy: still dropped the explicit
reference taken before schedule_delayed_work().
One second later vsock_pending_work() observed is_pending=true and
performed full cleanup: vsock_remove_pending() then the two trailing
sock_put(sk) calls -- the first reached refcount 0 and __sk_freed
the socket, and the second wrote into the freed object:
BUG: KASAN: slab-use-after-free in refcount_warn_saturate
Write of size 4 at addr ffff88800b1cac80 by task kworker
Workqueue: events vsock_pending_work
Treat peer RST like any other unexpected packet type (err = -EINVAL).
All destroy: arms now return err < 0, so vmci_transport_recv_listen()
removes pending from pending_links synchronously and
vsock_pending_work() takes the is_pending=false / !rejected branch,
dropping only its own work reference. This also closes the
multi-packet race Sashiko reported on v2: pending is removed from
the list before any subsequent packet can find it.
The pre-existing sk_acceptq_removed() gap on the err < 0 path of
vmci_transport_recv_listen() that Sashiko also noted is not
introduced or changed by this patch.
Tested on lts-6.12.79 with KASAN: 52/100 unpatched -> 0/100 patched.
CVSS Score
8.8
EPSS Score
0.001
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
scsi: isci: Fix use-after-free in device removal path
The ISCI completion tasklet is initialized in isci_host_alloc()
(drivers/scsi/isci/init.c:496) and scheduled from both MSI-X and legacy
interrupt handlers (drivers/scsi/isci/host.c:223,613).
isci_host_deinit() stops the controller and waits for stop completion,
but it never kills completion_tasklet before teardown continues. A
top-of-function tasklet_kill() is not sufficient here: interrupts are
only disabled when isci_host_stop_complete() runs, so until
wait_for_stop() returns the IRQ handlers can still requeue the
tasklet. The tasklet callback also re-enables interrupts after draining
completions, so killing the tasklet before the source is quiesced leaves
the same race open.
Once wait_for_stop() returns, no further IRQ-driven scheduling can
occur. Kill completion_tasklet there so teardown cannot race a queued
tasklet running on a dead ihost. On remove or unload, the stale callback
can otherwise dereference ihost and touch ihost->smu_registers after the
host lifetime ends.
A UML + KASAN analogue reproduced the failure class both with no
tasklet_kill() and with tasklet_kill() placed before source quiesce, and
stayed clean once the kill happened after quiescing the scheduling
source.
This mirrors commit f6ab594672d4 ("scsi: aic94xx: fix use-after-free in
device removal path"), but ISCI needs the kill after wait_for_stop().
CVSS Score
7.8
EPSS Score
0.002
Published
2026-07-19