Security Vulnerabilities
- CVEs Published In July 2025
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_conntrack: fix crash due to removal of uninitialised entry
A crash in conntrack was reported while trying to unlink the conntrack
entry from the hash bucket list:
[exception RIP: __nf_ct_delete_from_lists+172]
[..]
#7 [ff539b5a2b043aa0] nf_ct_delete at ffffffffc124d421 [nf_conntrack]
#8 [ff539b5a2b043ad0] nf_ct_gc_expired at ffffffffc124d999 [nf_conntrack]
#9 [ff539b5a2b043ae0] __nf_conntrack_find_get at ffffffffc124efbc [nf_conntrack]
[..]
The nf_conn struct is marked as allocated from slab but appears to be in
a partially initialised state:
ct hlist pointer is garbage; looks like the ct hash value
(hence crash).
ct->status is equal to IPS_CONFIRMED|IPS_DYING, which is expected
ct->timeout is 30000 (=30s), which is unexpected.
Everything else looks like normal udp conntrack entry. If we ignore
ct->status and pretend its 0, the entry matches those that are newly
allocated but not yet inserted into the hash:
- ct hlist pointers are overloaded and store/cache the raw tuple hash
- ct->timeout matches the relative time expected for a new udp flow
rather than the absolute 'jiffies' value.
If it were not for the presence of IPS_CONFIRMED,
__nf_conntrack_find_get() would have skipped the entry.
Theory is that we did hit following race:
cpu x cpu y cpu z
found entry E found entry E
E is expired <preemption>
nf_ct_delete()
return E to rcu slab
init_conntrack
E is re-inited,
ct->status set to 0
reply tuplehash hnnode.pprev
stores hash value.
cpu y found E right before it was deleted on cpu x.
E is now re-inited on cpu z. cpu y was preempted before
checking for expiry and/or confirm bit.
->refcnt set to 1
E now owned by skb
->timeout set to 30000
If cpu y were to resume now, it would observe E as
expired but would skip E due to missing CONFIRMED bit.
nf_conntrack_confirm gets called
sets: ct->status |= CONFIRMED
This is wrong: E is not yet added
to hashtable.
cpu y resumes, it observes E as expired but CONFIRMED:
<resumes>
nf_ct_expired()
-> yes (ct->timeout is 30s)
confirmed bit set.
cpu y will try to delete E from the hashtable:
nf_ct_delete() -> set DYING bit
__nf_ct_delete_from_lists
Even this scenario doesn't guarantee a crash:
cpu z still holds the table bucket lock(s) so y blocks:
wait for spinlock held by z
CONFIRMED is set but there is no
guarantee ct will be added to hash:
"chaintoolong" or "clash resolution"
logic both skip the insert step.
reply hnnode.pprev still stores the
hash value.
unlocks spinlock
return NF_DROP
<unblocks, then
crashes on hlist_nulls_del_rcu pprev>
In case CPU z does insert the entry into the hashtable, cpu y will unlink
E again right away but no crash occurs.
Without 'cpu y' race, 'garbage' hlist is of no consequence:
ct refcnt remains at 1, eventually skb will be free'd and E gets
destroyed via: nf_conntrack_put -> nf_conntrack_destroy -> nf_ct_destroy.
To resolve this, move the IPS_CONFIRMED assignment after the table
insertion but before the unlock.
Pablo points out that the confirm-bit-store could be reordered to happen
before hlist add resp. the timeout fixup, so switch to set_bit and
before_atomic memory barrier to prevent this.
It doesn't matter if other CPUs can observe a newly inserted entry right
before the CONFIRMED bit was set:
Such event cannot be distinguished from above "E is the old incarnation"
case: the entry will be skipped.
Also change nf_ct_should_gc() to first check the confirmed bit.
The gc sequence is:
1. Check if entry has expired, if not skip to next entry
2. Obtain a reference to the expired entry.
3. Call nf_ct_should_gc() to double-check step 1.
nf_ct_should_gc() is thus called only for entries that already failed an
expiry check. After this patch, once the confirmed bit check pas
---truncated---
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: Fix null-ptr-deref in l2cap_sock_resume_cb()
syzbot reported null-ptr-deref in l2cap_sock_resume_cb(). [0]
l2cap_sock_resume_cb() has a similar problem that was fixed by commit
1bff51ea59a9 ("Bluetooth: fix use-after-free error in lock_sock_nested()").
Since both l2cap_sock_kill() and l2cap_sock_resume_cb() are executed
under l2cap_sock_resume_cb(), we can avoid the issue simply by checking
if chan->data is NULL.
Let's not access to the killed socket in l2cap_sock_resume_cb().
[0]:
BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:82 [inline]
BUG: KASAN: null-ptr-deref in clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
BUG: KASAN: null-ptr-deref in l2cap_sock_resume_cb+0xb4/0x17c net/bluetooth/l2cap_sock.c:1711
Write of size 8 at addr 0000000000000570 by task kworker/u9:0/52
CPU: 1 UID: 0 PID: 52 Comm: kworker/u9:0 Not tainted 6.16.0-rc4-syzkaller-g7482bb149b9f #0 PREEMPT
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: hci0 hci_rx_work
Call trace:
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:501 (C)
__dump_stack+0x30/0x40 lib/dump_stack.c:94
dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
print_report+0x58/0x84 mm/kasan/report.c:524
kasan_report+0xb0/0x110 mm/kasan/report.c:634
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:189
__kasan_check_write+0x20/0x30 mm/kasan/shadow.c:37
instrument_atomic_write include/linux/instrumented.h:82 [inline]
clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
l2cap_sock_resume_cb+0xb4/0x17c net/bluetooth/l2cap_sock.c:1711
l2cap_security_cfm+0x524/0xea0 net/bluetooth/l2cap_core.c:7357
hci_auth_cfm include/net/bluetooth/hci_core.h:2092 [inline]
hci_auth_complete_evt+0x2e8/0xa4c net/bluetooth/hci_event.c:3514
hci_event_func net/bluetooth/hci_event.c:7511 [inline]
hci_event_packet+0x650/0xe9c net/bluetooth/hci_event.c:7565
hci_rx_work+0x320/0xb18 net/bluetooth/hci_core.c:4070
process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
process_scheduled_works kernel/workqueue.c:3321 [inline]
worker_thread+0x958/0xed8 kernel/workqueue.c:3402
kthread+0x5fc/0x75c kernel/kthread.c:464
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847
In the Linux kernel, the following vulnerability has been resolved:
usb: net: sierra: check for no status endpoint
The driver checks for having three endpoints and
having bulk in and out endpoints, but not that
the third endpoint is interrupt input.
Rectify the omission.
In the Linux kernel, the following vulnerability has been resolved:
smc: Fix various oops due to inet_sock type confusion.
syzbot reported weird splats [0][1] in cipso_v4_sock_setattr() while
freeing inet_sk(sk)->inet_opt.
The address was freed multiple times even though it was read-only memory.
cipso_v4_sock_setattr() did nothing wrong, and the root cause was type
confusion.
The cited commit made it possible to create smc_sock as an INET socket.
The issue is that struct smc_sock does not have struct inet_sock as the
first member but hijacks AF_INET and AF_INET6 sk_family, which confuses
various places.
In this case, inet_sock.inet_opt was actually smc_sock.clcsk_data_ready(),
which is an address of a function in the text segment.
$ pahole -C inet_sock vmlinux
struct inet_sock {
...
struct ip_options_rcu * inet_opt; /* 784 8 */
$ pahole -C smc_sock vmlinux
struct smc_sock {
...
void (*clcsk_data_ready)(struct sock *); /* 784 8 */
The same issue for another field was reported before. [2][3]
At that time, an ugly hack was suggested [4], but it makes both INET
and SMC code error-prone and hard to change.
Also, yet another variant was fixed by a hacky commit 98d4435efcbf3
("net/smc: prevent NULL pointer dereference in txopt_get").
Instead of papering over the root cause by such hacks, we should not
allow non-INET socket to reuse the INET infra.
Let's add inet_sock as the first member of smc_sock.
[0]:
kvfree_call_rcu(): Double-freed call. rcu_head 000000006921da73
WARNING: CPU: 0 PID: 6718 at mm/slab_common.c:1956 kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955
Modules linked in:
CPU: 0 UID: 0 PID: 6718 Comm: syz.0.17 Tainted: G W 6.16.0-rc4-syzkaller-g7482bb149b9f #0 PREEMPT
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955
lr : kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955
sp : ffff8000a03a7730
x29: ffff8000a03a7730 x28: 00000000fffffff5 x27: 1fffe000184823d3
x26: dfff800000000000 x25: ffff0000c2411e9e x24: ffff0000dd88da00
x23: ffff8000891ac9a0 x22: 00000000ffffffea x21: ffff8000891ac9a0
x20: ffff8000891ac9a0 x19: ffff80008afc2480 x18: 00000000ffffffff
x17: 0000000000000000 x16: ffff80008ae642c8 x15: ffff700011ede14c
x14: 1ffff00011ede14c x13: 0000000000000004 x12: ffffffffffffffff
x11: ffff700011ede14c x10: 0000000000ff0100 x9 : 5fa3c1ffaf0ff000
x8 : 5fa3c1ffaf0ff000 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff8000a03a7078 x4 : ffff80008f766c20 x3 : ffff80008054d360
x2 : 0000000000000000 x1 : 0000000000000201 x0 : 0000000000000000
Call trace:
kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 (P)
cipso_v4_sock_setattr+0x2f0/0x3f4 net/ipv4/cipso_ipv4.c:1914
netlbl_sock_setattr+0x240/0x334 net/netlabel/netlabel_kapi.c:1000
smack_netlbl_add+0xa8/0x158 security/smack/smack_lsm.c:2581
smack_inode_setsecurity+0x378/0x430 security/smack/smack_lsm.c:2912
security_inode_setsecurity+0x118/0x3c0 security/security.c:2706
__vfs_setxattr_noperm+0x174/0x5c4 fs/xattr.c:251
__vfs_setxattr_locked+0x1ec/0x218 fs/xattr.c:295
vfs_setxattr+0x158/0x2ac fs/xattr.c:321
do_setxattr fs/xattr.c:636 [inline]
file_setxattr+0x1b8/0x294 fs/xattr.c:646
path_setxattrat+0x2ac/0x320 fs/xattr.c:711
__do_sys_fsetxattr fs/xattr.c:761 [inline]
__se_sys_fsetxattr fs/xattr.c:758 [inline]
__arm64_sys_fsetxattr+0xc0/0xdc fs/xattr.c:758
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
[
---truncated---
In the Linux kernel, the following vulnerability has been resolved:
rpl: Fix use-after-free in rpl_do_srh_inline().
Running lwt_dst_cache_ref_loop.sh in selftest with KASAN triggers
the splat below [0].
rpl_do_srh_inline() fetches ipv6_hdr(skb) and accesses it after
skb_cow_head(), which is illegal as the header could be freed then.
Let's fix it by making oldhdr to a local struct instead of a pointer.
[0]:
[root@fedora net]# ./lwt_dst_cache_ref_loop.sh
...
TEST: rpl (input)
[ 57.631529] ==================================================================
BUG: KASAN: slab-use-after-free in rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)
Read of size 40 at addr ffff888122bf96d8 by task ping6/1543
CPU: 50 UID: 0 PID: 1543 Comm: ping6 Not tainted 6.16.0-rc5-01302-gfadd1e6231b1 #23 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl (lib/dump_stack.c:122)
print_report (mm/kasan/report.c:409 mm/kasan/report.c:521)
kasan_report (mm/kasan/report.c:221 mm/kasan/report.c:636)
kasan_check_range (mm/kasan/generic.c:175 (discriminator 1) mm/kasan/generic.c:189 (discriminator 1))
__asan_memmove (mm/kasan/shadow.c:94 (discriminator 2))
rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)
rpl_input (net/ipv6/rpl_iptunnel.c:201 net/ipv6/rpl_iptunnel.c:282)
lwtunnel_input (net/core/lwtunnel.c:459)
ipv6_rcv (./include/net/dst.h:471 (discriminator 1) ./include/net/dst.h:469 (discriminator 1) net/ipv6/ip6_input.c:79 (discriminator 1) ./include/linux/netfilter.h:317 (discriminator 1) ./include/linux/netfilter.h:311 (discriminator 1) net/ipv6/ip6_input.c:311 (discriminator 1))
__netif_receive_skb_one_core (net/core/dev.c:5967)
process_backlog (./include/linux/rcupdate.h:869 net/core/dev.c:6440)
__napi_poll.constprop.0 (net/core/dev.c:7452)
net_rx_action (net/core/dev.c:7518 net/core/dev.c:7643)
handle_softirqs (kernel/softirq.c:579)
do_softirq (kernel/softirq.c:480 (discriminator 20))
</IRQ>
<TASK>
__local_bh_enable_ip (kernel/softirq.c:407)
__dev_queue_xmit (net/core/dev.c:4740)
ip6_finish_output2 (./include/linux/netdevice.h:3358 ./include/net/neighbour.h:526 ./include/net/neighbour.h:540 net/ipv6/ip6_output.c:141)
ip6_finish_output (net/ipv6/ip6_output.c:215 net/ipv6/ip6_output.c:226)
ip6_output (./include/linux/netfilter.h:306 net/ipv6/ip6_output.c:248)
ip6_send_skb (net/ipv6/ip6_output.c:1983)
rawv6_sendmsg (net/ipv6/raw.c:588 net/ipv6/raw.c:918)
__sys_sendto (net/socket.c:714 (discriminator 1) net/socket.c:729 (discriminator 1) net/socket.c:2228 (discriminator 1))
__x64_sys_sendto (net/socket.c:2231)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
RIP: 0033:0x7f68cffb2a06
Code: 5d e8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 75 19 83 e2 39 83 fa 08 75 11 e8 26 ff ff ff 66 0f 1f 44 00 00 48 8b 45 10 0f 05 <48> 8b 5d f8 c9 c3 0f 1f 40 00 f3 0f 1e fa 55 48 89 e5 48 83 ec 08
RSP: 002b:00007ffefb7c53d0 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000564cd69f10a0 RCX: 00007f68cffb2a06
RDX: 0000000000000040 RSI: 0000564cd69f10a4 RDI: 0000000000000003
RBP: 00007ffefb7c53f0 R08: 0000564cd6a032ac R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000564cd69f10a4
R13: 0000000000000040 R14: 00007ffefb7c66e0 R15: 0000564cd69f10a0
</TASK>
Allocated by task 1543:
kasan_save_stack (mm/kasan/common.c:48)
kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1))
__kasan_slab_alloc (mm/kasan/common.c:319 mm/kasan/common.c:345)
kmem_cache_alloc_node_noprof (./include/linux/kasan.h:250 mm/slub.c:4148 mm/slub.c:4197 mm/slub.c:4249)
kmalloc_reserve (net/core/skbuff.c:581 (discriminator 88))
__alloc_skb (net/core/skbuff.c:669)
__ip6_append_data (net/ipv6/ip6_output.c:1672 (discriminator 1))
ip6_
---truncated---
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sch_qfq: Fix race condition on qfq_aggregate
A race condition can occur when 'agg' is modified in qfq_change_agg
(called during qfq_enqueue) while other threads access it
concurrently. For example, qfq_dump_class may trigger a NULL
dereference, and qfq_delete_class may cause a use-after-free.
This patch addresses the issue by:
1. Moved qfq_destroy_class into the critical section.
2. Added sch_tree_lock protection to qfq_dump_class and
qfq_dump_class_stats.
In the Linux kernel, the following vulnerability has been resolved:
comedi: Fix initialization of data for instructions that write to subdevice
Some Comedi subdevice instruction handlers are known to access
instruction data elements beyond the first `insn->n` elements in some
cases. The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions
allocate at least `MIN_SAMPLES` (16) data elements to deal with this,
but they do not initialize all of that. For Comedi instruction codes
that write to the subdevice, the first `insn->n` data elements are
copied from user-space, but the remaining elements are left
uninitialized. That could be a problem if the subdevice instruction
handler reads the uninitialized data. Ensure that the first
`MIN_SAMPLES` elements are initialized before calling these instruction
handlers, filling the uncopied elements with 0. For
`do_insnlist_ioctl()`, the same data buffer elements are used for
handling a list of instructions, so ensure the first `MIN_SAMPLES`
elements are initialized for each instruction that writes to the
subdevice.
In the Linux kernel, the following vulnerability has been resolved:
comedi: Fix use of uninitialized data in insn_rw_emulate_bits()
For Comedi `INSN_READ` and `INSN_WRITE` instructions on "digital"
subdevices (subdevice types `COMEDI_SUBD_DI`, `COMEDI_SUBD_DO`, and
`COMEDI_SUBD_DIO`), it is common for the subdevice driver not to have
`insn_read` and `insn_write` handler functions, but to have an
`insn_bits` handler function for handling Comedi `INSN_BITS`
instructions. In that case, the subdevice's `insn_read` and/or
`insn_write` function handler pointers are set to point to the
`insn_rw_emulate_bits()` function by `__comedi_device_postconfig()`.
For `INSN_WRITE`, `insn_rw_emulate_bits()` currently assumes that the
supplied `data[0]` value is a valid copy from user memory. It will at
least exist because `do_insnlist_ioctl()` and `do_insn_ioctl()` in
"comedi_fops.c" ensure at lease `MIN_SAMPLES` (16) elements are
allocated. However, if `insn->n` is 0 (which is allowable for
`INSN_READ` and `INSN_WRITE` instructions, then `data[0]` may contain
uninitialized data, and certainly contains invalid data, possibly from a
different instruction in the array of instructions handled by
`do_insnlist_ioctl()`. This will result in an incorrect value being
written to the digital output channel (or to the digital input/output
channel if configured as an output), and may be reflected in the
internal saved state of the channel.
Fix it by returning 0 early if `insn->n` is 0, before reaching the code
that accesses `data[0]`. Previously, the function always returned 1 on
success, but it is supposed to be the number of data samples actually
read or written up to `insn->n`, which is 0 in this case.
In the Linux kernel, the following vulnerability has been resolved:
comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
The handling of the `COMEDI_INSNLIST` ioctl allocates a kernel buffer to
hold the array of `struct comedi_insn`, getting the length from the
`n_insns` member of the `struct comedi_insnlist` supplied by the user.
The allocation will fail with a WARNING and a stack dump if it is too
large.
Avoid that by failing with an `-EINVAL` error if the supplied `n_insns`
value is unreasonable.
Define the limit on the `n_insns` value in the `MAX_INSNS` macro. Set
this to the same value as `MAX_SAMPLES` (65536), which is the maximum
allowed sum of the values of the member `n` in the array of `struct
comedi_insn`, and sensible comedi instructions will have an `n` of at
least 1.
In the Linux kernel, the following vulnerability has been resolved:
net/sched: Return NULL when htb_lookup_leaf encounters an empty rbtree
htb_lookup_leaf has a BUG_ON that can trigger with the following:
tc qdisc del dev lo root
tc qdisc add dev lo root handle 1: htb default 1
tc class add dev lo parent 1: classid 1:1 htb rate 64bit
tc qdisc add dev lo parent 1:1 handle 2: netem
tc qdisc add dev lo parent 2:1 handle 3: blackhole
ping -I lo -c1 -W0.001 127.0.0.1
The root cause is the following:
1. htb_dequeue calls htb_dequeue_tree which calls the dequeue handler on
the selected leaf qdisc
2. netem_dequeue calls enqueue on the child qdisc
3. blackhole_enqueue drops the packet and returns a value that is not
just NET_XMIT_SUCCESS
4. Because of this, netem_dequeue calls qdisc_tree_reduce_backlog, and
since qlen is now 0, it calls htb_qlen_notify -> htb_deactivate ->
htb_deactiviate_prios -> htb_remove_class_from_row -> htb_safe_rb_erase
5. As this is the only class in the selected hprio rbtree,
__rb_change_child in __rb_erase_augmented sets the rb_root pointer to
NULL
6. Because blackhole_dequeue returns NULL, netem_dequeue returns NULL,
which causes htb_dequeue_tree to call htb_lookup_leaf with the same
hprio rbtree, and fail the BUG_ON
The function graph for this scenario is shown here:
0) | htb_enqueue() {
0) + 13.635 us | netem_enqueue();
0) 4.719 us | htb_activate_prios();
0) # 2249.199 us | }
0) | htb_dequeue() {
0) 2.355 us | htb_lookup_leaf();
0) | netem_dequeue() {
0) + 11.061 us | blackhole_enqueue();
0) | qdisc_tree_reduce_backlog() {
0) | qdisc_lookup_rcu() {
0) 1.873 us | qdisc_match_from_root();
0) 6.292 us | }
0) 1.894 us | htb_search();
0) | htb_qlen_notify() {
0) 2.655 us | htb_deactivate_prios();
0) 6.933 us | }
0) + 25.227 us | }
0) 1.983 us | blackhole_dequeue();
0) + 86.553 us | }
0) # 2932.761 us | qdisc_warn_nonwc();
0) | htb_lookup_leaf() {
0) | BUG_ON();
------------------------------------------
The full original bug report can be seen here [1].
We can fix this just by returning NULL instead of the BUG_ON,
as htb_dequeue_tree returns NULL when htb_lookup_leaf returns
NULL.
[1] https://lore.kernel.org/netdev/pF5XOOIim0IuEfhI-SOxTgRvNoDwuux7UHKnE_Y5-zVd4wmGvNk2ceHjKb8ORnzw0cGwfmVu42g9dL7XyJLf1NEzaztboTWcm0Ogxuojoeo=@willsroot.io/