Linux: >> Linux Kernel >> 6.1.124 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
KEYS: trusted: Fix a memory leak in tpm2_load_cmd
'tpm2_load_cmd' allocates a tempoary blob indirectly via 'tpm2_key_decode'
but it is not freed in the failure paths. Address this by wrapping the blob
into with a cleanup helper.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-23
In the Linux kernel, the following vulnerability has been resolved:
io_uring/poll: correctly handle io_poll_add() return value on update
When the core of io_uring was updated to handle completions
consistently and with fixed return codes, the POLL_REMOVE opcode
with updates got slightly broken. If a POLL_ADD is pending and
then POLL_REMOVE is used to update the events of that request, if that
update causes the POLL_ADD to now trigger, then that completion is lost
and a CQE is never posted.
Additionally, ensure that if an update does cause an existing POLL_ADD
to complete, that the completion value isn't always overwritten with
-ECANCELED. For that case, whatever io_poll_add() set the value to
should just be retained.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-23
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: Fix refcount leak when invalid session is found on session lookup
When a session is found but its state is not SMB2_SESSION_VALID, It
indicates that no valid session was found, but it is missing to decrement
the reference count acquired by the session lookup, which results in
a reference count leak. This patch fixes the issue by explicitly calling
ksmbd_user_session_put to release the reference to the session.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-23
In the Linux kernel, the following vulnerability has been resolved:
net: sock: fix hardened usercopy panic in sock_recv_errqueue
skbuff_fclone_cache was created without defining a usercopy region,
[1] unlike skbuff_head_cache which properly whitelists the cb[] field.
[2] This causes a usercopy BUG() when CONFIG_HARDENED_USERCOPY is
enabled and the kernel attempts to copy sk_buff.cb data to userspace
via sock_recv_errqueue() -> put_cmsg().
The crash occurs when: 1. TCP allocates an skb using alloc_skb_fclone()
(from skbuff_fclone_cache) [1]
2. The skb is cloned via skb_clone() using the pre-allocated fclone
[3] 3. The cloned skb is queued to sk_error_queue for timestamp
reporting 4. Userspace reads the error queue via recvmsg(MSG_ERRQUEUE)
5. sock_recv_errqueue() calls put_cmsg() to copy serr->ee from skb->cb
[4] 6. __check_heap_object() fails because skbuff_fclone_cache has no
usercopy whitelist [5]
When cloned skbs allocated from skbuff_fclone_cache are used in the
socket error queue, accessing the sock_exterr_skb structure in skb->cb
via put_cmsg() triggers a usercopy hardening violation:
[ 5.379589] usercopy: Kernel memory exposure attempt detected from SLUB object 'skbuff_fclone_cache' (offset 296, size 16)!
[ 5.382796] kernel BUG at mm/usercopy.c:102!
[ 5.383923] Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
[ 5.384903] CPU: 1 UID: 0 PID: 138 Comm: poc_put_cmsg Not tainted 6.12.57 #7
[ 5.384903] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 5.384903] RIP: 0010:usercopy_abort+0x6c/0x80
[ 5.384903] Code: 1a 86 51 48 c7 c2 40 15 1a 86 41 52 48 c7 c7 c0 15 1a 86 48 0f 45 d6 48 c7 c6 80 15 1a 86 48 89 c1 49 0f 45 f3 e8 84 27 88 ff <0f> 0b 490
[ 5.384903] RSP: 0018:ffffc900006f77a8 EFLAGS: 00010246
[ 5.384903] RAX: 000000000000006f RBX: ffff88800f0ad2a8 RCX: 1ffffffff0f72e74
[ 5.384903] RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffffff87b973a0
[ 5.384903] RBP: 0000000000000010 R08: 0000000000000000 R09: fffffbfff0f72e74
[ 5.384903] R10: 0000000000000003 R11: 79706f6372657375 R12: 0000000000000001
[ 5.384903] R13: ffff88800f0ad2b8 R14: ffffea00003c2b40 R15: ffffea00003c2b00
[ 5.384903] FS: 0000000011bc4380(0000) GS:ffff8880bf100000(0000) knlGS:0000000000000000
[ 5.384903] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 5.384903] CR2: 000056aa3b8e5fe4 CR3: 000000000ea26004 CR4: 0000000000770ef0
[ 5.384903] PKRU: 55555554
[ 5.384903] Call Trace:
[ 5.384903] <TASK>
[ 5.384903] __check_heap_object+0x9a/0xd0
[ 5.384903] __check_object_size+0x46c/0x690
[ 5.384903] put_cmsg+0x129/0x5e0
[ 5.384903] sock_recv_errqueue+0x22f/0x380
[ 5.384903] tls_sw_recvmsg+0x7ed/0x1960
[ 5.384903] ? srso_alias_return_thunk+0x5/0xfbef5
[ 5.384903] ? schedule+0x6d/0x270
[ 5.384903] ? srso_alias_return_thunk+0x5/0xfbef5
[ 5.384903] ? mutex_unlock+0x81/0xd0
[ 5.384903] ? __pfx_mutex_unlock+0x10/0x10
[ 5.384903] ? __pfx_tls_sw_recvmsg+0x10/0x10
[ 5.384903] ? _raw_spin_lock_irqsave+0x8f/0xf0
[ 5.384903] ? _raw_read_unlock_irqrestore+0x20/0x40
[ 5.384903] ? srso_alias_return_thunk+0x5/0xfbef5
The crash offset 296 corresponds to skb2->cb within skbuff_fclones:
- sizeof(struct sk_buff) = 232 - offsetof(struct sk_buff, cb) = 40 -
offset of skb2.cb in fclones = 232 + 40 = 272 - crash offset 296 =
272 + 24 (inside sock_exterr_skb.ee)
This patch uses a local stack variable as a bounce buffer to avoid the hardened usercopy check failure.
[1] https://elixir.bootlin.com/linux/v6.12.62/source/net/ipv4/tcp.c#L885
[2] https://elixir.bootlin.com/linux/v6.12.62/source/net/core/skbuff.c#L5104
[3] https://elixir.bootlin.com/linux/v6.12.62/source/net/core/skbuff.c#L5566
[4] https://elixir.bootlin.com/linux/v6.12.62/source/net/core/skbuff.c#L5491
[5] https://elixir.bootlin.com/linux/v6.12.62/source/mm/slub.c#L5719
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-21
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sch_qfq: Fix NULL deref when deactivating inactive aggregate in qfq_reset
`qfq_class->leaf_qdisc->q.qlen > 0` does not imply that the class
itself is active.
Two qfq_class objects may point to the same leaf_qdisc. This happens
when:
1. one QFQ qdisc is attached to the dev as the root qdisc, and
2. another QFQ qdisc is temporarily referenced (e.g., via qdisc_get()
/ qdisc_put()) and is pending to be destroyed, as in function
tc_new_tfilter.
When packets are enqueued through the root QFQ qdisc, the shared
leaf_qdisc->q.qlen increases. At the same time, the second QFQ
qdisc triggers qdisc_put and qdisc_destroy: the qdisc enters
qfq_reset() with its own q->q.qlen == 0, but its class's leaf
qdisc->q.qlen > 0. Therefore, the qfq_reset would wrongly deactivate
an inactive aggregate and trigger a null-deref in qfq_deactivate_agg:
[ 0.903172] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 0.903571] #PF: supervisor write access in kernel mode
[ 0.903860] #PF: error_code(0x0002) - not-present page
[ 0.904177] PGD 10299b067 P4D 10299b067 PUD 10299c067 PMD 0
[ 0.904502] Oops: Oops: 0002 [#1] SMP NOPTI
[ 0.904737] CPU: 0 UID: 0 PID: 135 Comm: exploit Not tainted 6.19.0-rc3+ #2 NONE
[ 0.905157] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
[ 0.905754] RIP: 0010:qfq_deactivate_agg (include/linux/list.h:992 (discriminator 2) include/linux/list.h:1006 (discriminator 2) net/sched/sch_qfq.c:1367 (discriminator 2) net/sched/sch_qfq.c:1393 (discriminator 2))
[ 0.906046] Code: 0f 84 4d 01 00 00 48 89 70 18 8b 4b 10 48 c7 c2 ff ff ff ff 48 8b 78 08 48 d3 e2 48 21 f2 48 2b 13 48 8b 30 48 d3 ea 8b 4b 18 0
Code starting with the faulting instruction
===========================================
0: 0f 84 4d 01 00 00 je 0x153
6: 48 89 70 18 mov %rsi,0x18(%rax)
a: 8b 4b 10 mov 0x10(%rbx),%ecx
d: 48 c7 c2 ff ff ff ff mov $0xffffffffffffffff,%rdx
14: 48 8b 78 08 mov 0x8(%rax),%rdi
18: 48 d3 e2 shl %cl,%rdx
1b: 48 21 f2 and %rsi,%rdx
1e: 48 2b 13 sub (%rbx),%rdx
21: 48 8b 30 mov (%rax),%rsi
24: 48 d3 ea shr %cl,%rdx
27: 8b 4b 18 mov 0x18(%rbx),%ecx
...
[ 0.907095] RSP: 0018:ffffc900004a39a0 EFLAGS: 00010246
[ 0.907368] RAX: ffff8881043a0880 RBX: ffff888102953340 RCX: 0000000000000000
[ 0.907723] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 0.908100] RBP: ffff888102952180 R08: 0000000000000000 R09: 0000000000000000
[ 0.908451] R10: ffff8881043a0000 R11: 0000000000000000 R12: ffff888102952000
[ 0.908804] R13: ffff888102952180 R14: ffff8881043a0ad8 R15: ffff8881043a0880
[ 0.909179] FS: 000000002a1a0380(0000) GS:ffff888196d8d000(0000) knlGS:0000000000000000
[ 0.909572] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.909857] CR2: 0000000000000000 CR3: 0000000102993002 CR4: 0000000000772ef0
[ 0.910247] PKRU: 55555554
[ 0.910391] Call Trace:
[ 0.910527] <TASK>
[ 0.910638] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1485)
[ 0.910826] qdisc_reset (include/linux/skbuff.h:2195 include/linux/skbuff.h:2501 include/linux/skbuff.h:3424 include/linux/skbuff.h:3430 net/sched/sch_generic.c:1036)
[ 0.911040] __qdisc_destroy (net/sched/sch_generic.c:1076)
[ 0.911236] tc_new_tfilter (net/sched/cls_api.c:2447)
[ 0.911447] rtnetlink_rcv_msg (net/core/rtnetlink.c:6958)
[ 0.911663] ? __pfx_rtnetlink_rcv_msg (net/core/rtnetlink.c:6861)
[ 0.911894] netlink_rcv_skb (net/netlink/af_netlink.c:2550)
[ 0.912100] netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)
[ 0.912296] ? __alloc_skb (net/core/skbuff.c:706)
[ 0.912484] netlink_sendmsg (net/netlink/af
---truncated---
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-21
In the Linux kernel, the following vulnerability has been resolved:
iommu: disable SVA when CONFIG_X86 is set
Patch series "Fix stale IOTLB entries for kernel address space", v7.
This proposes a fix for a security vulnerability related to IOMMU Shared
Virtual Addressing (SVA). In an SVA context, an IOMMU can cache kernel
page table entries. When a kernel page table page is freed and
reallocated for another purpose, the IOMMU might still hold stale,
incorrect entries. This can be exploited to cause a use-after-free or
write-after-free condition, potentially leading to privilege escalation or
data corruption.
This solution introduces a deferred freeing mechanism for kernel page
table pages, which provides a safe window to notify the IOMMU to
invalidate its caches before the page is reused.
This patch (of 8):
In the IOMMU Shared Virtual Addressing (SVA) context, the IOMMU hardware
shares and walks the CPU's page tables. The x86 architecture maps the
kernel's virtual address space into the upper portion of every process's
page table. Consequently, in an SVA context, the IOMMU hardware can walk
and cache kernel page table entries.
The Linux kernel currently lacks a notification mechanism for kernel page
table changes, specifically when page table pages are freed and reused.
The IOMMU driver is only notified of changes to user virtual address
mappings. This can cause the IOMMU's internal caches to retain stale
entries for kernel VA.
Use-After-Free (UAF) and Write-After-Free (WAF) conditions arise when
kernel page table pages are freed and later reallocated. The IOMMU could
misinterpret the new data as valid page table entries. The IOMMU might
then walk into attacker-controlled memory, leading to arbitrary physical
memory DMA access or privilege escalation. This is also a
Write-After-Free issue, as the IOMMU will potentially continue to write
Accessed and Dirty bits to the freed memory while attempting to walk the
stale page tables.
Currently, SVA contexts are unprivileged and cannot access kernel
mappings. However, the IOMMU will still walk kernel-only page tables all
the way down to the leaf entries, where it realizes the mapping is for the
kernel and errors out. This means the IOMMU still caches these
intermediate page table entries, making the described vulnerability a real
concern.
Disable SVA on x86 architecture until the IOMMU can receive notification
to flush the paging cache before freeing the CPU kernel page table pages.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
ublk: fix deadlock when reading partition table
When one process(such as udev) opens ublk block device (e.g., to read
the partition table via bdev_open()), a deadlock[1] can occur:
1. bdev_open() grabs disk->open_mutex
2. The process issues read I/O to ublk backend to read partition table
3. In __ublk_complete_rq(), blk_update_request() or blk_mq_end_request()
runs bio->bi_end_io() callbacks
4. If this triggers fput() on file descriptor of ublk block device, the
work may be deferred to current task's task work (see fput() implementation)
5. This eventually calls blkdev_release() from the same context
6. blkdev_release() tries to grab disk->open_mutex again
7. Deadlock: same task waiting for a mutex it already holds
The fix is to run blk_update_request() and blk_mq_end_request() with bottom
halves disabled. This forces blkdev_release() to run in kernel work-queue
context instead of current task work context, and allows ublk server to make
forward progress, and avoids the deadlock.
[axboe: rewrite comment in ublk]
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix use-after-free in ksmbd_tree_connect_put under concurrency
Under high concurrency, A tree-connection object (tcon) is freed on
a disconnect path while another path still holds a reference and later
executes *_put()/write on it.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-01-13
In the Linux kernel, the following vulnerability has been resolved:
iomap: Fix possible overflow condition in iomap_write_delalloc_scan
folio_next_index() returns an unsigned long value which left shifted
by PAGE_SHIFT could possibly cause an overflow on 32-bit system. Instead
use folio_pos(folio) + folio_size(folio), which does this correctly.
CVSS Score
7.8
EPSS Score
0.0
Published
2025-12-30
In the Linux kernel, the following vulnerability has been resolved:
bpf: Do not let BPF test infra emit invalid GSO types to stack
Yinhao et al. reported that their fuzzer tool was able to trigger a
skb_warn_bad_offload() from netif_skb_features() -> gso_features_check().
When a BPF program - triggered via BPF test infra - pushes the packet
to the loopback device via bpf_clone_redirect() then mentioned offload
warning can be seen. GSO-related features are then rightfully disabled.
We get into this situation due to convert___skb_to_skb() setting
gso_segs and gso_size but not gso_type. Technically, it makes sense
that this warning triggers since the GSO properties are malformed due
to the gso_type. Potentially, the gso_type could be marked non-trustworthy
through setting it at least to SKB_GSO_DODGY without any other specific
assumptions, but that also feels wrong given we should not go further
into the GSO engine in the first place.
The checks were added in 121d57af308d ("gso: validate gso_type in GSO
handlers") because there were malicious (syzbot) senders that combine
a protocol with a non-matching gso_type. If we would want to drop such
packets, gso_features_check() currently only returns feature flags via
netif_skb_features(), so one location for potentially dropping such skbs
could be validate_xmit_unreadable_skb(), but then otoh it would be
an additional check in the fast-path for a very corner case. Given
bpf_clone_redirect() is the only place where BPF test infra could emit
such packets, lets reject them right there.
CVSS Score
5.5
EPSS Score
0.0
Published
2025-12-24