Linux: >> Linux Kernel >> 4.18.0-193.el8 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
bcache: fix cached_dev.sb_bio use-after-free and crash
In our production environment, we have received multiple crash reports
regarding libceph, which have caught our attention:
```
[6888366.280350] Call Trace:
[6888366.280452] blk_update_request+0x14e/0x370
[6888366.280561] blk_mq_end_request+0x1a/0x130
[6888366.280671] rbd_img_handle_request+0x1a0/0x1b0 [rbd]
[6888366.280792] rbd_obj_handle_request+0x32/0x40 [rbd]
[6888366.280903] __complete_request+0x22/0x70 [libceph]
[6888366.281032] osd_dispatch+0x15e/0xb40 [libceph]
[6888366.281164] ? inet_recvmsg+0x5b/0xd0
[6888366.281272] ? ceph_tcp_recvmsg+0x6f/0xa0 [libceph]
[6888366.281405] ceph_con_process_message+0x79/0x140 [libceph]
[6888366.281534] ceph_con_v1_try_read+0x5d7/0xf30 [libceph]
[6888366.281661] ceph_con_workfn+0x329/0x680 [libceph]
```
After analyzing the coredump file, we found that the address of
dc->sb_bio has been freed. We know that cached_dev is only freed when it
is stopped.
Since sb_bio is a part of struct cached_dev, rather than an alloc every
time. If the device is stopped while writing to the superblock, the
released address will be accessed at endio.
This patch hopes to wait for sb_write to complete in cached_dev_free.
It should be noted that we analyzed the cause of the problem, then tell
all details to the QWEN and adopted the modifications it made.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-24
In the Linux kernel, the following vulnerability has been resolved:
ALSA: 6fire: fix use-after-free on disconnect
In usb6fire_chip_abort(), the chip struct is allocated as the card's
private data (via snd_card_new with sizeof(struct sfire_chip)). When
snd_card_free_when_closed() is called and no file handles are open, the
card and embedded chip are freed synchronously. The subsequent
chip->card = NULL write then hits freed slab memory.
Call trace:
usb6fire_chip_abort sound/usb/6fire/chip.c:59 [inline]
usb6fire_chip_disconnect+0x348/0x358 sound/usb/6fire/chip.c:182
usb_unbind_interface+0x1a8/0x88c drivers/usb/core/driver.c:458
...
hub_event+0x1a04/0x4518 drivers/usb/core/hub.c:5953
Fix by moving the card lifecycle out of usb6fire_chip_abort() and into
usb6fire_chip_disconnect(). The card pointer is saved in a local
before any teardown, snd_card_disconnect() is called first to prevent
new opens, URBs are aborted while chip is still valid, and
snd_card_free_when_closed() is called last so chip is never accessed
after the card may be freed.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-24
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (powerz) Fix use-after-free on USB disconnect
After powerz_disconnect() frees the URB and releases the mutex, a
subsequent powerz_read() call can acquire the mutex and call
powerz_read_data(), which dereferences the freed URB pointer.
Fix by:
- Setting priv->urb to NULL in powerz_disconnect() so that
powerz_read_data() can detect the disconnected state.
- Adding a !priv->urb check at the start of powerz_read_data()
to return -ENODEV on a disconnected device.
- Moving usb_set_intfdata() before hwmon registration so the
disconnect handler can always find the priv pointer.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-24
In the Linux kernel, the following vulnerability has been resolved:
net: bonding: fix NULL deref in bond_debug_rlb_hash_show
rlb_clear_slave intentionally keeps RLB hash-table entries on
the rx_hashtbl_used_head list with slave set to NULL when no
replacement slave is available. However, bond_debug_rlb_hash_show
visites client_info->slave without checking if it's NULL.
Other used-list iterators in bond_alb.c already handle this NULL-slave
state safely:
- rlb_update_client returns early on !client_info->slave
- rlb_req_update_slave_clients, rlb_clear_slave, and rlb_rebalance
compare slave values before visiting
- lb_req_update_subnet_clients continues if slave is NULL
The following NULL deref crash can be trigger in
bond_debug_rlb_hash_show:
[ 1.289791] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 1.292058] RIP: 0010:bond_debug_rlb_hash_show (drivers/net/bonding/bond_debugfs.c:41)
[ 1.293101] RSP: 0018:ffffc900004a7d00 EFLAGS: 00010286
[ 1.293333] RAX: 0000000000000000 RBX: ffff888102b48200 RCX: ffff888102b48204
[ 1.293631] RDX: ffff888102b48200 RSI: ffffffff839daad5 RDI: ffff888102815078
[ 1.293924] RBP: ffff888102815078 R08: ffff888102b4820e R09: 0000000000000000
[ 1.294267] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888100f929c0
[ 1.294564] R13: ffff888100f92a00 R14: 0000000000000001 R15: ffffc900004a7ed8
[ 1.294864] FS: 0000000001395380(0000) GS:ffff888196e75000(0000) knlGS:0000000000000000
[ 1.295239] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1.295480] CR2: 0000000000000000 CR3: 0000000102adc004 CR4: 0000000000772ef0
[ 1.295897] Call Trace:
[ 1.296134] seq_read_iter (fs/seq_file.c:231)
[ 1.296341] seq_read (fs/seq_file.c:164)
[ 1.296493] full_proxy_read (fs/debugfs/file.c:378 (discriminator 1))
[ 1.296658] vfs_read (fs/read_write.c:572)
[ 1.296981] ksys_read (fs/read_write.c:717)
[ 1.297132] do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
[ 1.297325] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
Add a NULL check and print "(none)" for entries with no assigned slave.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-24
In the Linux kernel, the following vulnerability has been resolved:
drm/i915/gt: Check set_default_submission() before deferencing
When the i915 driver firmware binaries are not present, the
set_default_submission pointer is not set. This pointer is
dereferenced during suspend anyways.
Add a check to make sure it is set before dereferencing.
[ 23.289926] PM: suspend entry (deep)
[ 23.293558] Filesystems sync: 0.000 seconds
[ 23.298010] Freezing user space processes
[ 23.302771] Freezing user space processes completed (elapsed 0.000 seconds)
[ 23.309766] OOM killer disabled.
[ 23.313027] Freezing remaining freezable tasks
[ 23.318540] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[ 23.342038] serial 00:05: disabled
[ 23.345719] serial 00:02: disabled
[ 23.349342] serial 00:01: disabled
[ 23.353782] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 23.358993] sd 1:0:0:0: [sdb] Synchronizing SCSI cache
[ 23.361635] ata1.00: Entering standby power mode
[ 23.368863] ata2.00: Entering standby power mode
[ 23.445187] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 23.452194] #PF: supervisor instruction fetch in kernel mode
[ 23.457896] #PF: error_code(0x0010) - not-present page
[ 23.463065] PGD 0 P4D 0
[ 23.465640] Oops: Oops: 0010 [#1] SMP NOPTI
[ 23.469869] CPU: 8 UID: 0 PID: 211 Comm: kworker/u48:18 Tainted: G S W 6.19.0-rc4-00020-gf0b9d8eb98df #10 PREEMPT(voluntary)
[ 23.482512] Tainted: [S]=CPU_OUT_OF_SPEC, [W]=WARN
[ 23.496511] Workqueue: async async_run_entry_fn
[ 23.501087] RIP: 0010:0x0
[ 23.503755] Code: Unable to access opcode bytes at 0xffffffffffffffd6.
[ 23.510324] RSP: 0018:ffffb4a60065fca8 EFLAGS: 00010246
[ 23.515592] RAX: 0000000000000000 RBX: ffff9f428290e000 RCX: 000000000000000f
[ 23.522765] RDX: 0000000000000000 RSI: 0000000000000282 RDI: ffff9f428290e000
[ 23.529937] RBP: ffff9f4282907070 R08: ffff9f4281130428 R09: 00000000ffffffff
[ 23.537111] R10: 0000000000000000 R11: 0000000000000001 R12: ffff9f42829070f8
[ 23.544284] R13: ffff9f4282906028 R14: ffff9f4282900000 R15: ffff9f4282906b68
[ 23.551457] FS: 0000000000000000(0000) GS:ffff9f466b2cf000(0000) knlGS:0000000000000000
[ 23.559588] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 23.565365] CR2: ffffffffffffffd6 CR3: 000000031c230001 CR4: 0000000000f70ef0
[ 23.572539] PKRU: 55555554
[ 23.575281] Call Trace:
[ 23.577770] <TASK>
[ 23.579905] intel_engines_reset_default_submission+0x42/0x60
[ 23.585695] __intel_gt_unset_wedged+0x191/0x200
[ 23.590360] intel_gt_unset_wedged+0x20/0x40
[ 23.594675] gt_sanitize+0x15e/0x170
[ 23.598290] i915_gem_suspend_late+0x6b/0x180
[ 23.602692] i915_drm_suspend_late+0x35/0xf0
[ 23.607008] ? __pfx_pci_pm_suspend_late+0x10/0x10
[ 23.611843] dpm_run_callback+0x78/0x1c0
[ 23.615817] device_suspend_late+0xde/0x2e0
[ 23.620037] async_suspend_late+0x18/0x30
[ 23.624082] async_run_entry_fn+0x25/0xa0
[ 23.628129] process_one_work+0x15b/0x380
[ 23.632182] worker_thread+0x2a5/0x3c0
[ 23.635973] ? __pfx_worker_thread+0x10/0x10
[ 23.640279] kthread+0xf6/0x1f0
[ 23.643464] ? __pfx_kthread+0x10/0x10
[ 23.647263] ? __pfx_kthread+0x10/0x10
[ 23.651045] ret_from_fork+0x131/0x190
[ 23.654837] ? __pfx_kthread+0x10/0x10
[ 23.658634] ret_from_fork_asm+0x1a/0x30
[ 23.662597] </TASK>
[ 23.664826] Modules linked in:
[ 23.667914] CR2: 0000000000000000
[ 23.671271] ------------[ cut here ]------------
(cherry picked from commit daa199abc3d3d1740c9e3a2c3e9216ae5b447cad)
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-24
In the Linux kernel, the following vulnerability has been resolved:
can: raw: fix ro->uniq use-after-free in raw_rcv()
raw_release() unregisters raw CAN receive filters via can_rx_unregister(),
but receiver deletion is deferred with call_rcu(). This leaves a window
where raw_rcv() may still be running in an RCU read-side critical section
after raw_release() frees ro->uniq, leading to a use-after-free of the
percpu uniq storage.
Move free_percpu(ro->uniq) out of raw_release() and into a raw-specific
socket destructor. can_rx_unregister() takes an extra reference to the
socket and only drops it from the RCU callback, so freeing uniq from
sk_destruct ensures the percpu area is not released until the relevant
callbacks have drained.
[mkl: applied manually]
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-23
In the Linux kernel, the following vulnerability has been resolved:
HID: asus: avoid memory leak in asus_report_fixup()
The asus_report_fixup() function was returning a newly allocated
kmemdup()-allocated buffer, but never freeing it. Switch to
devm_kzalloc() to ensure the memory is managed and freed automatically
when the device is removed.
The caller of report_fixup() does not take ownership of the returned
pointer, but it is permitted to return a pointer whose lifetime is at
least that of the input buffer.
Also fix a harmless out-of-bounds read by copying only the original
descriptor size.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
driver core: platform: use generic driver_override infrastructure
When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.
Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.
Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
xfrm: prevent policy_hthresh.work from racing with netns teardown
A XFRM_MSG_NEWSPDINFO request can queue the per-net work item
policy_hthresh.work onto the system workqueue.
The queued callback, xfrm_hash_rebuild(), retrieves the enclosing
struct net via container_of(). If the net namespace is torn down
before that work runs, the associated struct net may already have
been freed, and xfrm_hash_rebuild() may then dereference stale memory.
xfrm_policy_fini() already flushes policy_hash_work during teardown,
but it does not synchronize policy_hthresh.work.
Synchronize policy_hthresh.work in xfrm_policy_fini() as well, so the
queued work cannot outlive the net namespace teardown and access a
freed struct net.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-22
In the Linux kernel, the following vulnerability has been resolved:
btrfs: set BTRFS_ROOT_ORPHAN_CLEANUP during subvol create
We have recently observed a number of subvolumes with broken dentries.
ls-ing the parent dir looks like:
drwxrwxrwt 1 root root 16 Jan 23 16:49 .
drwxr-xr-x 1 root root 24 Jan 23 16:48 ..
d????????? ? ? ? ? ? broken_subvol
and similarly stat-ing the file fails.
In this state, deleting the subvol fails with ENOENT, but attempting to
create a new file or subvol over it errors out with EEXIST and even
aborts the fs. Which leaves us a bit stuck.
dmesg contains a single notable error message reading:
"could not do orphan cleanup -2"
2 is ENOENT and the error comes from the failure handling path of
btrfs_orphan_cleanup(), with the stack leading back up to
btrfs_lookup().
btrfs_lookup
btrfs_lookup_dentry
btrfs_orphan_cleanup // prints that message and returns -ENOENT
After some detailed inspection of the internal state, it became clear
that:
- there are no orphan items for the subvol
- the subvol is otherwise healthy looking, it is not half-deleted or
anything, there is no drop progress, etc.
- the subvol was created a while ago and does the meaningful first
btrfs_orphan_cleanup() call that sets BTRFS_ROOT_ORPHAN_CLEANUP much
later.
- after btrfs_orphan_cleanup() fails, btrfs_lookup_dentry() returns -ENOENT,
which results in a negative dentry for the subvolume via
d_splice_alias(NULL, dentry), leading to the observed behavior. The
bug can be mitigated by dropping the dentry cache, at which point we
can successfully delete the subvolume if we want.
i.e.,
btrfs_lookup()
btrfs_lookup_dentry()
if (!sb_rdonly(inode->vfs_inode)->vfs_inode)
btrfs_orphan_cleanup(sub_root)
test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)
btrfs_search_slot() // finds orphan item for inode N
...
prints "could not do orphan cleanup -2"
if (inode == ERR_PTR(-ENOENT))
inode = NULL;
return d_splice_alias(NULL, dentry) // NEGATIVE DENTRY for valid subvolume
btrfs_orphan_cleanup() does test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)
on the root when it runs, so it cannot run more than once on a given
root, so something else must run concurrently. However, the obvious
routes to deleting an orphan when nlinks goes to 0 should not be able to
run without first doing a lookup into the subvolume, which should run
btrfs_orphan_cleanup() and set the bit.
The final important observation is that create_subvol() calls
d_instantiate_new() but does not set BTRFS_ROOT_ORPHAN_CLEANUP, so if
the dentry cache gets dropped, the next lookup into the subvolume will
make a real call into btrfs_orphan_cleanup() for the first time. This
opens up the possibility of concurrently deleting the inode/orphan items
but most typical evict() paths will be holding a reference on the parent
dentry (child dentry holds parent->d_lockref.count via dget in
d_alloc(), released in __dentry_kill()) and prevent the parent from
being removed from the dentry cache.
The one exception is delayed iputs. Ordered extent creation calls
igrab() on the inode. If the file is unlinked and closed while those
refs are held, iput() in __dentry_kill() decrements i_count but does
not trigger eviction (i_count > 0). The child dentry is freed and the
subvol dentry's d_lockref.count drops to 0, making it evictable while
the inode is still alive.
Since there are two races (the race between writeback and unlink and
the race between lookup and delayed iputs), and there are too many moving
parts, the following three diagrams show the complete picture.
(Only the second and third are races)
Phase 1:
Create Subvol in dentry cache without BTRFS_ROOT_ORPHAN_CLEANUP set
btrfs_mksubvol()
lookup_one_len()
__lookup_slow()
d_alloc_parallel()
__d_alloc() // d_lockref.count = 1
create_subvol(dentry)
// doesn't touch the bit..
d_instantiate_new(dentry, inode) // dentry in cache with d_lockref.c
---truncated---
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-22