Linux: >> Linux Kernel >> 4.7.5 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
serial: caif: fix use-after-free in caif_serial ldisc_close()
There is a use-after-free bug in caif_serial where handle_tx() may
access ser->tty after the tty has been freed.
The race condition occurs between ldisc_close() and packet transmission:
CPU 0 (close) CPU 1 (xmit)
------------- ------------
ldisc_close()
tty_kref_put(ser->tty)
[tty may be freed here]
<-- race window -->
caif_xmit()
handle_tx()
tty = ser->tty // dangling ptr
tty->ops->write() // UAF!
schedule_work()
ser_release()
unregister_netdevice()
The root cause is that tty_kref_put() is called in ldisc_close() while
the network device is still active and can receive packets.
Since ser and tty have a 1:1 binding relationship with consistent
lifecycles (ser is allocated in ldisc_open and freed in ser_release
via unregister_netdevice, and each ser binds exactly one tty), we can
safely defer the tty reference release to ser_release() where the
network device is unregistered.
Fix this by moving tty_kref_put() from ldisc_close() to ser_release(),
after unregister_netdevice(). This ensures the tty reference is held
as long as the network device exists, preventing the UAF.
Note: We save ser->tty before unregister_netdevice() because ser is
embedded in netdev's private data and will be freed along with netdev
(needs_free_netdev = true).
How to reproduce: Add mdelay(500) at the beginning of ldisc_close()
to widen the race window, then run the reproducer program [1].
Note: There is a separate deadloop issue in handle_tx() when using
PORT_UNKNOWN serial ports (e.g., /dev/ttyS3 in QEMU without proper
serial backend). This deadloop exists even without this patch,
and is likely caused by inconsistency between uart_write_room() and
uart_write() in serial core. It has been addressed in a separate
patch [2].
KASAN report:
==================================================================
BUG: KASAN: slab-use-after-free in handle_tx+0x5d1/0x620
Read of size 1 at addr ffff8881131e1490 by task caif_uaf_trigge/9929
Call Trace:
<TASK>
dump_stack_lvl+0x10e/0x1f0
print_report+0xd0/0x630
kasan_report+0xe4/0x120
handle_tx+0x5d1/0x620
dev_hard_start_xmit+0x9d/0x6c0
__dev_queue_xmit+0x6e2/0x4410
packet_xmit+0x243/0x360
packet_sendmsg+0x26cf/0x5500
__sys_sendto+0x4a3/0x520
__x64_sys_sendto+0xe0/0x1c0
do_syscall_64+0xc9/0xf80
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f615df2c0d7
Allocated by task 9930:
Freed by task 64:
Last potentially related work creation:
The buggy address belongs to the object at ffff8881131e1000
which belongs to the cache kmalloc-cg-2k of size 2048
The buggy address is located 1168 bytes inside of
freed 2048-byte region [ffff8881131e1000, ffff8881131e1800)
The buggy address belongs to the physical page:
page_owner tracks the page as allocated
page last free pid 9778 tgid 9778 stack trace:
Memory state around the buggy address:
ffff8881131e1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881131e1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881131e1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881131e1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881131e1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
[1]: https://gist.github.com/mrpre/f683f244544f7b11e7fa87df9e6c2eeb
[2]: https://lore.kernel.org/linux-serial/20260204074327.226165-1-jiayuan.chen@linux.dev/T/#u
CVSS Score
7.8
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
scsi: csiostor: Fix dereference of null pointer rn
The error exit path when rn is NULL ends up deferencing the null pointer rn
via the use of the macro CSIO_INC_STATS. Fix this by adding a new error
return path label after the use of the macro to avoid the deference.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1
When allocating initialized blocks from a large unwritten extent, or
when splitting an unwritten extent during end I/O and converting it to
initialized, there is currently a potential issue of stale data if the
extent needs to be split in the middle.
0 A B N
[UUUUUUUUUUUU] U: unwritten extent
[--DDDDDDDD--] D: valid data
|<- ->| ----> this range needs to be initialized
ext4_split_extent() first try to split this extent at B with
EXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but
ext4_split_extent_at() failed to split this extent due to temporary lack
of space. It zeroout B to N and mark the entire extent from 0 to N
as written.
0 A B N
[WWWWWWWWWWWW] W: written extent
[SSDDDDDDDDZZ] Z: zeroed, S: stale data
ext4_split_extent() then try to split this extent at A with
EXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and left
a stale written extent from 0 to A.
0 A B N
[WW|WWWWWWWWWW]
[SS|DDDDDDDDZZ]
Fix this by pass EXT4_EXT_DATA_PARTIAL_VALID1 to ext4_split_extent_at()
when splitting at B, don't convert the entire extent to written and left
it as unwritten after zeroing out B to N. The remaining work is just
like the standard two-part split. ext4_split_extent() will pass the
EXT4_EXT_DATA_VALID2 flag when it calls ext4_split_extent_at() for the
second time, allowing it to properly handle the split. If the split is
successful, it will keep extent from 0 to A as unwritten.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
ipvs: skip ipv6 extension headers for csum checks
Protocol checksum validation fails for IPv6 if there are extension
headers before the protocol header. iph->len already contains its
offset, so use it to fix the problem.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
smack: /smack/doi: accept previously used values
Writing to /smack/doi a value that has ever been
written there in the past disables networking for
non-ambient labels.
E.g.
# cat /smack/doi
3
# netlabelctl -p cipso list
Configured CIPSO mappings (1)
DOI value : 3
mapping type : PASS_THROUGH
# netlabelctl -p map list
Configured NetLabel domain mappings (3)
domain: "_" (IPv4)
protocol: UNLABELED
domain: DEFAULT (IPv4)
protocol: CIPSO, DOI = 3
domain: DEFAULT (IPv6)
protocol: UNLABELED
# cat /smack/ambient
_
# cat /proc/$$/attr/smack/current
_
# ping -c1 10.1.95.12
64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.964 ms
# echo foo >/proc/$$/attr/smack/current
# ping -c1 10.1.95.12
64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.956 ms
unknown option 86
# echo 4 >/smack/doi
# echo 3 >/smack/doi
!> [ 214.050395] smk_cipso_doi:691 cipso add rc = -17
# echo 3 >/smack/doi
!> [ 249.402261] smk_cipso_doi:678 remove rc = -2
!> [ 249.402261] smk_cipso_doi:691 cipso add rc = -17
# ping -c1 10.1.95.12
!!> ping: 10.1.95.12: Address family for hostname not supported
# echo _ >/proc/$$/attr/smack/current
# ping -c1 10.1.95.12
64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.617 ms
This happens because Smack keeps decommissioned DOIs,
fails to re-add them, and consequently refuses to add
the “default” domain map:
# netlabelctl -p cipso list
Configured CIPSO mappings (2)
DOI value : 3
mapping type : PASS_THROUGH
DOI value : 4
mapping type : PASS_THROUGH
# netlabelctl -p map list
Configured NetLabel domain mappings (2)
domain: "_" (IPv4)
protocol: UNLABELED
!> (no ipv4 map for default domain here)
domain: DEFAULT (IPv6)
protocol: UNLABELED
Fix by clearing decommissioned DOI definitions and
serializing concurrent DOI updates with a new lock.
Also:
- allow /smack/doi to live unconfigured, since
adding a map (netlbl_cfg_cipsov4_map_add) may fail.
CIPSO_V4_DOI_UNKNOWN(0) indicates the unconfigured DOI
- add new DOI before removing the old default map,
so the old map remains if the add fails
(2008-02-04, Casey Schaufler)
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
openvswitch: cap upcall PID array size and pre-size vport replies
The vport netlink reply helpers allocate a fixed-size skb with
nlmsg_new(NLMSG_DEFAULT_SIZE, ...) but serialize the full upcall PID
array via ovs_vport_get_upcall_portids(). Since
ovs_vport_set_upcall_portids() accepts any non-zero multiple of
sizeof(u32) with no upper bound, a CAP_NET_ADMIN user can install a PID
array large enough to overflow the reply buffer, causing nla_put() to
fail with -EMSGSIZE and hitting BUG_ON(err < 0). On systems with
unprivileged user namespaces enabled (e.g., Ubuntu default), this is
reachable via unshare -Urn since OVS vport mutation operations use
GENL_UNS_ADMIN_PERM.
kernel BUG at net/openvswitch/datapath.c:2414!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 1 UID: 0 PID: 65 Comm: poc Not tainted 7.0.0-rc7-00195-geb216e422044 #1
RIP: 0010:ovs_vport_cmd_set+0x34c/0x400
Call Trace:
<TASK>
genl_family_rcv_msg_doit (net/netlink/genetlink.c:1116)
genl_rcv_msg (net/netlink/genetlink.c:1194)
netlink_rcv_skb (net/netlink/af_netlink.c:2550)
genl_rcv (net/netlink/genetlink.c:1219)
netlink_unicast (net/netlink/af_netlink.c:1344)
netlink_sendmsg (net/netlink/af_netlink.c:1894)
__sys_sendto (net/socket.c:2206)
__x64_sys_sendto (net/socket.c:2209)
do_syscall_64 (arch/x86/entry/syscall_64.c:63)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
</TASK>
Kernel panic - not syncing: Fatal exception
Reject attempts to set more PIDs than nr_cpu_ids in
ovs_vport_set_upcall_portids(), and pre-compute the worst-case reply
size in ovs_vport_cmd_msg_size() based on that bound, similar to the
existing ovs_dp_cmd_msg_size(). nr_cpu_ids matches the cap already
used by the per-CPU dispatch configuration on the datapath side
(ovs_dp_cmd_fill_info() serialises at most nr_cpu_ids PIDs), so the
two sides stay consistent.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO
nf_osf_match_one() computes ctx->window % f->wss.val in the
OSF_WSS_MODULO branch with no guard for f->wss.val == 0. A
CAP_NET_ADMIN user can add such a fingerprint via nfnetlink; a
subsequent matching TCP SYN divides by zero and panics the kernel.
Reject the bogus fingerprint in nfnl_osf_add_callback() above the
per-option for-loop. f->wss is per-fingerprint, not per-option, so
the check must run regardless of f->opt_num (including 0). Also
reject wss.wc >= OSF_WSS_MAX; nf_osf_match_one() already treats that
as "should not happen".
Crash:
Oops: divide error: 0000 [#1] SMP KASAN NOPTI
RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)
Call Trace:
<IRQ>
nf_osf_match (net/netfilter/nfnetlink_osf.c:220)
xt_osf_match_packet (net/netfilter/xt_osf.c:32)
ipt_do_table (net/ipv4/netfilter/ip_tables.c:348)
nf_hook_slow (net/netfilter/core.c:622)
ip_local_deliver (net/ipv4/ip_input.c:265)
ip_rcv (include/linux/skbuff.h:1162)
__netif_receive_skb_one_core (net/core/dev.c:6181)
process_backlog (net/core/dev.c:6642)
__napi_poll (net/core/dev.c:7710)
net_rx_action (net/core/dev.c:7945)
handle_softirqs (kernel/softirq.c:622)
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
slip: reject VJ receive packets on instances with no rstate array
slhc_init() accepts rslots == 0 as a valid configuration, with the
documented meaning of 'no receive compression'. In that case the
allocation loop in slhc_init() is skipped, so comp->rstate stays
NULL and comp->rslot_limit stays 0 (from the kzalloc of struct
slcompress).
The receive helpers do not defend against that configuration.
slhc_uncompress() dereferences comp->rstate[x] when the VJ header
carries an explicit connection ID, and slhc_remember() later assigns
cs = &comp->rstate[...] after only comparing the packet's slot number
to comp->rslot_limit. Because rslot_limit is 0, slot 0 passes the
range check, and the code dereferences a NULL rstate.
The configuration is reachable in-tree through PPP. PPPIOCSMAXCID
stores its argument in a signed int, and (val >> 16) uses arithmetic
shift. Passing 0xffff0000 therefore sign-extends to -1, so val2 + 1
is 0 and ppp_generic.c ends up calling slhc_init(0, 1). Because
/dev/ppp open is gated by ns_capable(CAP_NET_ADMIN), the whole path
is reachable from an unprivileged user namespace. Once the malformed
VJ state is installed, any inbound VJ-compressed or VJ-uncompressed
frame that selects slot 0 crashes the kernel in softirq context:
Oops: general protection fault, probably for non-canonical
address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
RIP: 0010:slhc_uncompress (drivers/net/slip/slhc.c:519)
Call Trace:
<TASK>
ppp_receive_nonmp_frame (drivers/net/ppp/ppp_generic.c:2466)
ppp_input (drivers/net/ppp/ppp_generic.c:2359)
ppp_async_process (drivers/net/ppp/ppp_async.c:492)
tasklet_action_common (kernel/softirq.c:926)
handle_softirqs (kernel/softirq.c:623)
run_ksoftirqd (kernel/softirq.c:1055)
smpboot_thread_fn (kernel/smpboot.c:160)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:164)
</TASK>
Reject the receive side on such instances instead of touching rstate.
slhc_uncompress() falls through to its existing 'bad' label, which
bumps sls_i_error and enters the toss state. slhc_remember() mirrors
that with an explicit sls_i_error increment followed by slhc_toss();
the sls_i_runt counter is not used here because a missing rstate is
an internal configuration state, not a runt packet.
The transmit path is unaffected: the only in-tree caller that picks
rslots from userspace (ppp_generic.c) still supplies tslots >= 1, and
slip.c always calls slhc_init(16, 16), so comp->tstate remains valid
and slhc_compress() continues to work.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
slip: bound decode() reads against the compressed packet length
slhc_uncompress() parses a VJ-compressed TCP header by advancing a
pointer through the packet via decode() and pull16(). Neither helper
bounds-checks against isize, and decode() masks its return with
& 0xffff so it can never return the -1 that callers test for -- those
error paths are dead code.
A short compressed frame whose change byte requests optional fields
lets decode() read past the end of the packet. The over-read bytes
are folded into the cached cstate and reflected into subsequent
reconstructed packets.
Make decode() and pull16() take the packet end pointer and return -1
when exhausted. Add a bounds check before the TCP-checksum read.
The existing == -1 tests now do what they were always meant to.
CVSS Score
8.2
EPSS Score
0.003
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
netfilter: arp_tables: fix IEEE1394 ARP payload parsing
Weiming Shi says:
"arp_packet_match() unconditionally parses the ARP payload assuming two
hardware addresses are present (source and target). However,
IPv4-over-IEEE1394 ARP (RFC 2734) omits the target hardware address
field, and arp_hdr_len() already accounts for this by returning a
shorter length for ARPHRD_IEEE1394 devices.
As a result, on IEEE1394 interfaces arp_packet_match() advances past a
nonexistent target hardware address and reads the wrong bytes for both
the target device address comparison and the target IP address. This
causes arptables rules to match against garbage data, leading to
incorrect filtering decisions: packets that should be accepted may be
dropped and vice versa.
The ARP stack in net/ipv4/arp.c (arp_create and arp_process) already
handles this correctly by skipping the target hardware address for
ARPHRD_IEEE1394. Apply the same pattern to arp_packet_match()."
Mangle the original patch to always return 0 (no match) in case user
matches on the target hardware address which is never present in
IEEE1394.
Note that this returns 0 (no match) for either normal and inverse match
because matching in the target hardware address in ARPHRD_IEEE1394 has
never been supported by arptables. This is intentional, matching on the
target hardware address should never evaluate true for ARPHRD_IEEE1394.
Moreover, adjust arpt_mangle to drop the packet too as AI suggests:
In arpt_mangle, the logic assumes a standard ARP layout. Because
IEEE1394 (FireWire) omits the target hardware address, the linear
pointer arithmetic miscalculates the offset for the target IP address.
This causes mangling operations to write to the wrong location, leading
to packet corruption. To ensure safety, this patch drops packets
(NF_DROP) when mangling is requested for these fields on IEEE1394
devices, as the current implementation cannot correctly map the FireWire
ARP payload.
This omits both mangling target hardware and IP address. Even if IP
address mangling should be possible in IEEE1394, this would require
to adjust arpt_mangle offset calculation, which has never been
supported.
Based on patch from Weiming Shi <bestswngs@gmail.com>.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-27