| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
netfilter: cttimeout: detach dataplane timeout policy and repurpose refcount
Add a refcount for struct nf_ct_timeout which is used by ct extension to
set the custom ct timeout policy, this tells us that the ct timeout is
being used by a conntrack entry. When the last conntrack entry drops the
refcount on the ct timeout, the ct timeout is released.
Remove the refcount for control plane which controls if the ruleset
refers to the timeout policy. After this update, it is possible to
remove the ct timeout policy from nfnetlink_cttimeout immediately.
This is for simplicity not to handle two refcounts on a single object.
Remove nf_queue_nf_hook_drop(): a packet sitting in nfqueue will just
hold a reference to the nf_ct_timeout object until packet is reinjected,
since this is part of the ct extension, this will be released by the
time the conntrack is freed.
nf_ct_untimeout() is still called to clean up in a best effort basis:
the ct timeout on existing entries gets removed when the ct timeout goes
away, but as long as the iptables ruleset still refers to the ct timeout
through a template, new conntracks may keep attaching it and extend its
lifetime until the rule is removed.
nf_ct_untimeout() is not called anymore from module removal path, this
is unlikely to find timeouts give module refcount is bumped, and the new
refcount already tracks the ct timeout policy use so it is released when
unused. |
| In the Linux kernel, the following vulnerability has been resolved:
ASoC: meson: aiu: Validate written enum values
The AIU HDMI and internal codec mux put callbacks use the written enum
value with snd_soc_enum_item_to_val() before checking whether the value is
valid for the enumeration.
Reject out-of-range values before converting the enum item, matching the
validation already done by the G12A HDMI and internal codec mux controls. |
| In the Linux kernel, the following vulnerability has been resolved:
ipv4: fib: Don't dump dying fib_info in fib_leaf_notify().
syzbot reported use-after-free in nsim_fib4_prepare_event(). [0]
The problem is that the following functions call fib_info_hold() /
refcount_inc() while dumping fib_info under RCU, which is unsafe.
* mlxsw_sp_router_fib4_event()
* rocker_router_fib_event()
* nsim_fib4_prepare_event()
refcount_inc_not_zero() must be used, but it would be too late
there.
Let's guarantee the lifetime of fib_info in fib_leaf_notify().
Note that IPv6 does not need the corresponding change since
fib6_table_dump() holds fib6_table.tb6_lock.
[0]:
refcount_t: addition on 0; use-after-free.
WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25, CPU#0: kworker/u8:15/3420
Modules linked in:
CPU: 0 UID: 0 PID: 3420 Comm: kworker/u8:15 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: netns cleanup_net
RIP: 0010:refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25
Code: eb 66 85 db 74 3e 83 fb 01 75 4c e8 1b f1 22 fd 48 8d 3d 84 cb f1 0a 67 48 0f b9 3a eb 4a e8 08 f1 22 fd 48 8d 3d 81 cb f1 0a <67> 48 0f b9 3a eb 37 e8 f5 f0 22 fd 48 8d 3d 7e cb f1 0a 67 48 0f
RSP: 0018:ffffc9000f2c7270 EFLAGS: 00010293
RAX: ffffffff84a18858 RBX: 0000000000000002 RCX: ffff888032ff9ec0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8f9353e0
RBP: 0000000000000000 R08: ffff888032ff9ec0 R09: 0000000000000005
R10: 0000000000000100 R11: 0000000000000004 R12: ffff8880570cc000
R13: dffffc0000000000 R14: ffff88802b40563c R15: ffff8880570cc000
FS: 0000000000000000(0000) GS:ffff888126173000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb1f4d5d000 CR3: 000000006072a000 CR4: 00000000003526f0
Call Trace:
<TASK>
__refcount_add include/linux/refcount.h:-1 [inline]
__refcount_inc include/linux/refcount.h:366 [inline]
refcount_inc include/linux/refcount.h:383 [inline]
fib_info_hold include/net/ip_fib.h:629 [inline]
nsim_fib4_prepare_event drivers/net/netdevsim/fib.c:930 [inline]
nsim_fib_event_schedule_work drivers/net/netdevsim/fib.c:1000 [inline]
nsim_fib_event_nb+0x1055/0x1240 drivers/net/netdevsim/fib.c:1043
call_fib_notifier+0x45/0x80 net/core/fib_notifier.c:25
call_fib_entry_notifier net/ipv4/fib_trie.c:90 [inline]
fib_leaf_notify net/ipv4/fib_trie.c:2176 [inline]
fib_table_notify net/ipv4/fib_trie.c:2194 [inline]
fib_notify+0x36b/0x5e0 net/ipv4/fib_trie.c:2217
fib_net_dump net/core/fib_notifier.c:70 [inline]
register_fib_notifier+0x184/0x360 net/core/fib_notifier.c:108
nsim_fib_create+0x85d/0x9f0 drivers/net/netdevsim/fib.c:1596
nsim_dev_reload_create drivers/net/netdevsim/dev.c:1604 [inline]
nsim_dev_reload_up+0x374/0x7c0 drivers/net/netdevsim/dev.c:1058
devlink_reload+0x501/0x8d0 net/devlink/dev.c:475
devlink_pernet_pre_exit+0x1ff/0x420 net/devlink/core.c:558
ops_pre_exit_list net/core/net_namespace.c:161 [inline]
ops_undo_list+0x187/0x940 net/core/net_namespace.c:234
cleanup_net+0x56e/0x800 net/core/net_namespace.c:702
process_one_work kernel/workqueue.c:3314 [inline]
process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3397
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3478
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK> |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: Guard __get_user acesss with access_ok for uprobe_multi data
As reported by sashiko [1] we need to use access_ok to check the user
space data bounds before we use __get-user to get it.
[1] https://lore.kernel.org/bpf/20260610145235.CB1441F00893@smtp.kernel.org/ |
| In the Linux kernel, the following vulnerability has been resolved:
coresight: platform: defer connection counter increment until alloc succeeds
coresight_add_out_conn() increments nr_outconns before calling
devm_krealloc_array() and again before devm_kmalloc(). If either
allocation fails, the counter is already bumped while the corresponding
array entry is NULL or uninitialized garbage.
coresight_add_in_conn() has the same problem with nr_inconns and
devm_krealloc_array().
In both cases the probe returns -ENOMEM, which causes
coresight_get_platform_data() to call coresight_release_platform_data()
for cleanup. That function iterates up to nr_outconns (or nr_inconns)
entries and dereferences each pointer unconditionally, hitting the NULL
or garbage entry and panicking instead of failing gracefully.
Fix by moving the counter increments to after all allocations succeed,
so the struct is always consistent on any error path. |
| In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: ISO: fix malformed ISO_END/CONT handling
Core specification (Part C vol 4 sec 5.4.5) does not exclude empty
ISO_CONT, ISO_END packets. We currently reject them if they are last.
If controller sends malformed sequence
ISO_START -> rx_len = 4, ISO_CONT skb->len 4, ISO_START
that ends payload in ISO_CONT, we leak conn->rx_skb. If controller sends
too long ISO_END, we panic on skb_put. If controller sends too short
ISO_END we accept it.
Fix by marking unfinished ISO_START via conn->rx_skb != NULL. Check
skb->len properly before skb_put. Combine the ISO_CONT/END code paths
as they require the same initial checks. Reject too short ISO_END
packets. |
| In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix busy dentry warning on unmount after DIO
Commit c68337442f03 ("cifs: Fix busy dentry used after unmounting") fixed
the issue in cifs where deferred close of a file led to a dentry reference
count not being released in umount, by flushing deferredclose_wq in
cifs_kill_sb() to solve it.
However, the cifs DIO path suffers from the same busy-dentry problem caused
by a delayed dentry reference-count release:
[dio] [cifsd] [close + umount]
netfs_unbuffered_write_iter_locked
...
cifs_demultiplex_thread
netfs_unbuffered_write
cifs_issue_write
netfs_wait_for_in_progress_stream [1]
...
netfs_write_subrequest_terminated
netfs_subreq_clear_in_progress
netfs_wake_collector // wake [1]
netfs_put_subrequest
netfs_put_request
queue_work(system_dfl_wq, xxx) [2]
// dio write return cifs_close
_cifsFileInfo_put
// cfile->count 2->1
--cfile->count [3]
// umount
cifs_kill_sb
kill_anon_super
// warning triggered!
shrink_dcache_for_umount [4]
[system_dfl_wq] [5]
netfs_free_request
...
_cifsFileInfo_put
// cfile->count 1->0
--cfile->count
queue_work(fileinfo_put_wq, xxx)
[fileinfo_put_wq] [6]
cifsFileInfo_put_work
cifsFileInfo_put_final
dput
If the umount path is triggered before [5], it results warning:
BUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1)
[unmount of cifs cifs]
The existing per-inode ictx->io_count wait in cifs_evict_inode() does not
help: it lives in the inode eviction path, which runs after
shrink_dcache_for_umount() has already warned about the busy dentries.
Fix it by adding a per-superblock outstanding-rreq counter that is
incremented in cifs_init_request() and decremented in cifs_free_request().
In cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach
0 - which guarantees that all cleanup_work for this sb have run and thus
all relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq.
Then drain the workqueue so the dentry refs are dropped.
This is a targeted wait, not a flush of the system-wide system_dfl_wq. |
| In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: mgmt: hold reference for hci_conn in mgmt_pending_cmds
Dereferencing RCU-protected pointers outside critical sections is
invalid and may lead to UAF. Use of hci_conn in hci_sync callbacks also
needs to hold refcount to avoid UAF.
Take appropriate locks for hci_conn lookups, and take refcount for
hci_conn pointers stored in mgmt_pending_cmd so that the pointer stays
valid.
When accessing conn->state, ensure hdev->lock is held to avoid data
race. |
| In the Linux kernel, the following vulnerability has been resolved:
drop_monitor: fix size calculations for 64-bit attributes
net_dm_packet_report_fill() and net_dm_hw_packet_report_fill() use
nla_put_u64_64bit() to append 64-bit attributes (NET_DM_ATTR_PC and
NET_DM_ATTR_TIMESTAMP).
On 32-bit architectures without CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS,
nla_put_u64_64bit() may append a 4-byte NET_DM_ATTR_PAD attribute for
64-bit alignment.
However, net_dm_packet_report_size() and net_dm_hw_packet_report_size()
used nla_total_size(sizeof(u64)) instead of nla_total_size_64bit(sizeof(u64)),
budgeting 12 bytes instead of up to 16 bytes.
This under-estimation of SKB size can lead to an skb_over_panic() when
__nla_reserve() or skb_put() is subsequently called.
Fix this by using nla_total_size_64bit(sizeof(u64)) in both size calculations. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: set new_stream to NULL after release
In dm_update_crtc_state(), the skip_modeset path releases new_stream
via dc_stream_release() but does not set the pointer to NULL.
If a later error (e.g., color management failure) triggers the fail
label, the error path calls dc_stream_release() again on the same
dangling pointer, causing a double release and potential use-after-free.
Fix this by setting new_stream to NULL after the initial release.
(cherry picked from commit 99f3af19073b3ddbfd96e789124cce12c4277b28) |
| In the Linux kernel, the following vulnerability has been resolved:
libceph: Reject monmaps advertising zero monitors
A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a
monitor to the client. This monmap contains information about the
existing monitors in the cluster. Currently, a monmap indicating that
there are zero monitors in the cluster is treated as valid. However, it
is impossible to have zero monitors in the cluster and still receive a
valid monmap from a monitor. Therefore, such a monmap must be corrupted
and should be treated as invalid. Furthermore, a monmap with a monitor
count of zero can subsequently crash the client when attempting to open
a session with a monitor in __open_session(). This happens because the
"BUG_ON(monc->monmap->num_mon < 1)" assertion in pick_new_mon() is
triggered.
This patch extends a check in ceph_monmap_decode() to also reject
arriving mon_maps with num_mon == 0 rather than only with
num_mon > CEPH_MAX_MON.
[ idryomov: drop "log output for unusual values of num_mon" part ] |
| In the Linux kernel, the following vulnerability has been resolved:
ksmbd: validate ACE size against SID sub-authorities
set_ntacl_dacl() validates sid.num_subauth before copying an ACE, but
does not verify that the declared ACE size contains all sub-authorities
described by that field. An undersized ACE can therefore be copied
and later make the POSIX ACL deduplication walk inspect data beyond
the copied ACE boundary.
The existing initial bound check is also too small. It only ensures
that the ACE size field is accessible before set_ntacl_dacl() reads
sid.num_subauth farther into the input buffer.
Require enough input for the fixed SID header before accessing
num_subauth, reject ACEs smaller than that header, and skip ACEs
whose declared size cannot contain the complete SID. This makes the
validation consistent with the other ACE walk paths. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: Fix shadow paging use-after-free due to unexpected role
Commit 0cb2af2ea66ad ("KVM: x86: Fix shadow paging use-after-free due
to unexpected GFN") fixed a shadow paging mismatch between stored and
computed GFNs; the bug could be triggered by changing a PDE mapping from
outside the guest, and then deleting a memslot. The rmap_remove()
call would miss entries created after the PDE change because the GFN
of the leaf SPTE does not match the GFN of the struct kvm_mmu_page.
A similar hole however remains if the modified PDE points to a non-leaf
page. In this case the gfn can be made to match, but the role does not
match: the original large 2MB page creates a kvm_mmu_page with direct=1,
while the new 4KB needs a kvm_mmu_page with direct=0. However,
kvm_mmu_get_child_sp() does not compare the role, and therefore reuses
the page.
The next step is installing a leaf (4KB) SPTE on the new path which
records an rmap entry under the gfn resolved by the walk. But when
that child is zapped its parent kvm_mmu_page has direct=1 and
kvm_mmu_page_get_gfn() computes the gfn for the 4KB page as
sp->gfn + index instead of using sp->shadowed_translation[] (or sp->gfns[]
in older kernels). It therefore fails to remove the recorded entry.
When the memslot is dropped the shadow page is freed but the rmap
entry survives, as in the scenario that was already fixed. Code that
later walks that gfn (dirty logging, MMU notifier invalidation, and
so on) dereferences an sptep that lies in the freed page, causing the
use-after-free. |
| In the Linux kernel, the following vulnerability has been resolved:
af_unix: Drop all SCM attributes for SOCKMAP.
SOCKMAP can hide inflight fd from AF_UNIX GC.
When a socket in SOCKMAP receives skb with inflight fd,
sk_psock_verdict_data_ready() looks up the mapped socket and
enqueue skb to its psock->ingress_skb.
Since neither the old nor the new GC can inspect the psock
queue, the hidden skb leaks the inflight sockets. Note that
this cannot be detected via kmemleak because inflight sockets
are linked to a global list.
In addition, SOCKMAP redirect breaks the Tarjan-based GC's
assumption that unix_edge.successor is always alive, which
is no longer true once skb is redirected, resulting in
use-after-free below. [0]
Moreover, SOCKMAP does not call scm_stat_del() properly,
so unix_show_fdinfo() could report an incorrect fd count.
sk_msg_recvmsg() does not support any SCM attributes in the
first place.
Let's drop all SCM attributes before passing skb to the
SOCKMAP layer.
[0]:
BUG: KASAN: slab-use-after-free in unix_del_edges (net/unix/garbage.c:118 net/unix/garbage.c:181 net/unix/garbage.c:251)
Read of size 8 at addr ffff888125362670 by task kworker/56:1/496
CPU: 56 UID: 0 PID: 496 Comm: kworker/56:1 Not tainted 7.0.0-rc7-00263-gb9d8b856689d #3 PREEMPT(lazy)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
Workqueue: events sk_psock_backlog
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:122)
print_report (mm/kasan/report.c:379)
kasan_report (mm/kasan/report.c:597)
unix_del_edges (net/unix/garbage.c:118 net/unix/garbage.c:181 net/unix/garbage.c:251)
unix_destroy_fpl (net/unix/garbage.c:317)
unix_destruct_scm (./include/net/scm.h:80 ./include/net/scm.h:86 net/unix/af_unix.c:1976)
sk_psock_backlog (./include/linux/skbuff.h:?)
process_scheduled_works (kernel/workqueue.c:?)
worker_thread (kernel/workqueue.c:?)
kthread (kernel/kthread.c:438)
ret_from_fork (arch/x86/kernel/process.c:164)
ret_from_fork_asm (arch/x86/entry/entry_64.S:258)
</TASK>
Allocated by task 955:
kasan_save_track (mm/kasan/common.c:58 mm/kasan/common.c:78)
__kasan_slab_alloc (mm/kasan/common.c:369)
kmem_cache_alloc_noprof (mm/slub.c:4539)
sk_prot_alloc (net/core/sock.c:2240)
sk_alloc (net/core/sock.c:2301)
unix_create1 (net/unix/af_unix.c:1099)
unix_create (net/unix/af_unix.c:1169)
__sock_create (net/socket.c:1606)
__sys_socketpair (net/socket.c:1811)
__x64_sys_socketpair (net/socket.c:1863 net/socket.c:1860 net/socket.c:1860)
do_syscall_64 (arch/x86/entry/syscall_64.c:?)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
Freed by task 496:
kasan_save_track (mm/kasan/common.c:58 mm/kasan/common.c:78)
kasan_save_free_info (mm/kasan/generic.c:587)
__kasan_slab_free (mm/kasan/common.c:287)
kmem_cache_free (mm/slub.c:6165)
__sk_destruct (net/core/sock.c:2282 net/core/sock.c:2384)
sk_psock_destroy (./include/net/sock.h:?)
process_scheduled_works (kernel/workqueue.c:?)
worker_thread (kernel/workqueue.c:?)
kthread (kernel/kthread.c:438)
ret_from_fork (arch/x86/kernel/process.c:164)
ret_from_fork_asm (arch/x86/entry/entry_64.S:258) |
| In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_tables: join hook list via splice_list_rcu() in commit phase
Publish new hooks in the list into the basechain/flowtable using
splice_list_rcu() to ensure netlink dump list traversal via rcu is safe
while concurrent ruleset update is going on. |
| In the Linux kernel, the following vulnerability has been resolved:
eventpoll: fix ep_remove struct eventpoll / struct file UAF
ep_remove() (via ep_remove_file()) cleared file->f_ep under
file->f_lock but then kept using @file inside the critical section
(is_file_epoll(), hlist_del_rcu() through the head, spin_unlock).
A concurrent __fput() taking the eventpoll_release() fastpath in
that window observed the transient NULL, skipped
eventpoll_release_file() and ran to f_op->release / file_free().
For the epoll-watches-epoll case, f_op->release is
ep_eventpoll_release() -> ep_clear_and_put() -> ep_free(), which
kfree()s the watched struct eventpoll. Its embedded ->refs
hlist_head is exactly where epi->fllink.pprev points, so the
subsequent hlist_del_rcu()'s "*pprev = next" scribbles into freed
kmalloc-192 memory.
In addition, struct file is SLAB_TYPESAFE_BY_RCU, so the slot
backing @file could be recycled by alloc_empty_file() --
reinitializing f_lock and f_ep -- while ep_remove() is still
nominally inside that lock. The upshot is an attacker-controllable
kmem_cache_free() against the wrong slab cache.
Pin @file via epi_fget() at the top of ep_remove() and gate the
critical section on the pin succeeding. With the pin held @file
cannot reach refcount zero, which holds __fput() off and
transitively keeps the watched struct eventpoll alive across the
hlist_del_rcu() and the f_lock use, closing both UAFs.
If the pin fails @file has already reached refcount zero and its
__fput() is in flight. Because we bailed before clearing f_ep,
that path takes the eventpoll_release() slow path into
eventpoll_release_file() and blocks on ep->mtx until the waiter
side's ep_clear_and_put() drops it. The bailed epi's share of
ep->refcount stays intact, so the trailing ep_refcount_dec_and_test()
in ep_clear_and_put() cannot free the eventpoll out from under
eventpoll_release_file(); the orphaned epi is then cleaned up
there.
A successful pin also proves we are not racing
eventpoll_release_file() on this epi, so drop the now-redundant
re-check of epi->dying under f_lock. The cheap lockless
READ_ONCE(epi->dying) fast-path bailout stays. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: Fix shadow paging use-after-free due to unexpected GFN
The shadow MMU computes GFNs for direct shadow pages using sp->gfn plus
the SPTE index. This assumption breaks for shadow paging if the guest
page tables are modified between VM entries (similar to commit
aad885e77496, "KVM: x86/mmu: Drop/zap existing present SPTE even
when creating an MMIO SPTE", 2026-03-27). The flow is as follows:
- a PDE is installed for a 2MB mapping, and a page in that area is
accessed. KVM creates a kvm_mmu_page consisting of 512 4KB pages;
the kvm_mmu_page is marked by FNAME(fetch) as direct-mapped because
the guest's mapping is a huge page (and thus contiguous).
- the PDE mapping is changed from outside the guest.
- the guest accesses another page in the same 2MB area. KVM installs
a new leaf SPTE and rmap entry; the SPTE uses the "correct" GFN
(i.e. based on the new mapping, as changed in the previous step) but
that GFN is outside of the [sp->gfn, sp->gfn + 511] range; therefore
the rmap entry cannot be found and removed when the kvm_mmu_page
is zapped.
- the memslot that covers the first 2MB mapping is deleted, and the
kvm_mmu_page for the now-invalid GPA is zapped. However, rmap_remove()
only looks at the [sp->gfn, sp->gfn + 511] range established in step 1,
and fails to find the rmap entry that was recorded by step 3.
- any operation that causes an rmap walk for the same page accessed
by step 3 then walks a stale rmap and dereferences a freed kvm_mmu_page.
This includes dirty logging or MMU notifier invalidations (e.g., from
MADV_DONTNEED).
The underlying issue is that KVM's walking of shadow PTEs assumes that
if a SPTE is present when KVM wants to install a non-leaf SPTE, then the
existing kvm_mmu_page must be for the correct gfn. Because the only way
for the gfn to be wrong is if KVM messed up and failed to zap a SPTE...
which shouldn't happen, but *actually* only happens in response to a
guest write.
That bug dates back literally forever, as even the first version of KVM
assumes that the GFN matches and walks into the "wrong" shadow page.
However, that was only an imprecision until 2032a93d66fa ("KVM: MMU:
Don't allocate gfns page for direct mmu pages") came along.
Fix it by checking for a target gfn mismatch and zapping the existing
SPTE. That way the old SP and rmap entries are gone, KVM installs
the rmap in the right location, and everyone is happy. |
| In the Linux kernel, the following vulnerability has been resolved:
landlock: Fix handling of disconnected directories
Disconnected files or directories can appear when they are visible and
opened from a bind mount, but have been renamed or moved from the source
of the bind mount in a way that makes them inaccessible from the mount
point (i.e. out of scope).
Previously, access rights tied to files or directories opened through a
disconnected directory were collected by walking the related hierarchy
down to the root of the filesystem, without taking into account the
mount point because it couldn't be found. This could lead to
inconsistent access results, potential access right widening, and
hard-to-debug renames, especially since such paths cannot be printed.
For a sandboxed task to create a disconnected directory, it needs to
have write access (i.e. FS_MAKE_REG, FS_REMOVE_FILE, and FS_REFER) to
the underlying source of the bind mount, and read access to the related
mount point. Because a sandboxed task cannot acquire more access
rights than those defined by its Landlock domain, this could lead to
inconsistent access rights due to missing permissions that should be
inherited from the mount point hierarchy, while inheriting permissions
from the filesystem hierarchy hidden by this mount point instead.
Landlock now handles files and directories opened from disconnected
directories by taking into account the filesystem hierarchy when the
mount point is not found in the hierarchy walk, and also always taking
into account the mount point from which these disconnected directories
were opened. This ensures that a rename is not allowed if it would
widen access rights [1].
The rationale is that, even if disconnected hierarchies might not be
visible or accessible to a sandboxed task, relying on the collected
access rights from them improves the guarantee that access rights will
not be widened during a rename because of the access right comparison
between the source and the destination (see LANDLOCK_ACCESS_FS_REFER).
It may look like this would grant more access on disconnected files and
directories, but the security policies are always enforced for all the
evaluated hierarchies. This new behavior should be less surprising to
users and safer from an access control perspective.
Remove a wrong WARN_ON_ONCE() canary in collect_domain_accesses() and
fix the related comment.
Because opened files have their access rights stored in the related file
security properties, there is no impact for disconnected or unlinked
files. |
| In the Linux kernel, the following vulnerability has been resolved:
eventpoll: don't decrement ep refcount while still holding the ep mutex
Jann Horn points out that epoll is decrementing the ep refcount and then
doing a
mutex_unlock(&ep->mtx);
afterwards. That's very wrong, because it can lead to a use-after-free.
That pattern is actually fine for the very last reference, because the
code in question will delay the actual call to "ep_free(ep)" until after
it has unlocked the mutex.
But it's wrong for the much subtler "next to last" case when somebody
*else* may also be dropping their reference and free the ep while we're
still using the mutex.
Note that this is true even if that other user is also using the same ep
mutex: mutexes, unlike spinlocks, can not be used for object ownership,
even if they guarantee mutual exclusion.
A mutex "unlock" operation is not atomic, and as one user is still
accessing the mutex as part of unlocking it, another user can come in
and get the now released mutex and free the data structure while the
first user is still cleaning up.
See our mutex documentation in Documentation/locking/mutex-design.rst,
in particular the section [1] about semantics:
"mutex_unlock() may access the mutex structure even after it has
internally released the lock already - so it's not safe for
another context to acquire the mutex and assume that the
mutex_unlock() context is not using the structure anymore"
So if we drop our ep ref before the mutex unlock, but we weren't the
last one, we may then unlock the mutex, another user comes in, drops
_their_ reference and releases the 'ep' as it now has no users - all
while the mutex_unlock() is still accessing it.
Fix this by simply moving the ep refcount dropping to outside the mutex:
the refcount itself is atomic, and doesn't need mutex protection (that's
the whole _point_ of refcounts: unlike mutexes, they are inherently
about object lifetimes). |
| In the Linux kernel, the following vulnerability has been resolved:
ipv6: mcast: extend RCU protection in igmp6_send()
igmp6_send() can be called without RTNL or RCU being held.
Extend RCU protection so that we can safely fetch the net pointer
and avoid a potential UAF.
Note that we no longer can use sock_alloc_send_skb() because
ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep.
Instead use alloc_skb() and charge the net->ipv6.igmp_sk
socket under RCU protection. |
