Linux: >> Linux Kernel >> 5.15.210 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
hwrng: core - use RCU and work_struct to fix race condition
Currently, hwrng_fill is not cleared until the hwrng_fillfn() thread
exits. Since hwrng_unregister() reads hwrng_fill outside the rng_mutex
lock, a concurrent hwrng_unregister() may call kthread_stop() again on
the same task.
Additionally, if hwrng_unregister() is called immediately after
hwrng_register(), the stopped thread may have never been executed. Thus,
hwrng_fill remains dirty even after hwrng_unregister() returns. In this
case, subsequent calls to hwrng_register() will fail to start new
threads, and hwrng_unregister() will call kthread_stop() on the same
freed task. In both cases, a use-after-free occurs:
refcount_t: addition on 0; use-after-free.
WARNING: ... at lib/refcount.c:25 refcount_warn_saturate+0xec/0x1c0
Call Trace:
kthread_stop+0x181/0x360
hwrng_unregister+0x288/0x380
virtrng_remove+0xe3/0x200
This patch fixes the race by protecting the global hwrng_fill pointer
inside the rng_mutex lock, so that hwrng_fillfn() thread is stopped only
once, and calls to kthread_run() and kthread_stop() are serialized
with the lock held.
To avoid deadlock in hwrng_fillfn() while being stopped with the lock
held, we convert current_rng to RCU, so that get_current_rng() can read
current_rng without holding the lock. To remove the lock from put_rng(),
we also delay the actual cleanup into a work_struct.
Since get_current_rng() no longer returns ERR_PTR values, the IS_ERR()
checks are removed from its callers.
With hwrng_fill protected by the rng_mutex lock, hwrng_fillfn() can no
longer clear hwrng_fill itself. Therefore, if hwrng_fillfn() returns
directly after current_rng is dropped, kthread_stop() would be called on
a freed task_struct later. To fix this, hwrng_fillfn() calls schedule()
now to keep the task alive until being stopped. The kthread_stop() call
is also moved from hwrng_unregister() to drop_current_rng(), ensuring
kthread_stop() is called on all possible paths where current_rng becomes
NULL, so that the thread would not wait forever.
CVSS Score
4.7
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
net: stmmac: fix oops when split header is enabled
For GMAC4, when split header is enabled, in some rare cases, the
hardware does not fill buf2 of the first descriptor with payload.
Thus we cannot assume buf2 is always fully filled if it is not
the last descriptor. Otherwise, the length of buf2 of the second
descriptor will be calculated wrong and cause an oops:
Unable to handle kernel paging request at virtual address ffff00019246bfc0
...
x2 : 0000000000000040 x1 : ffff00019246bfc0 x0 : ffff00009246c000
Call trace:
dcache_inval_poc+0x28/0x58 (P)
dma_direct_sync_single_for_cpu+0x38/0x6c
__dma_sync_single_for_cpu+0x34/0x6c
stmmac_napi_poll_rx+0x8f0/0xb60
__napi_poll.constprop.0+0x30/0x144
net_rx_action+0x160/0x274
handle_softirqs+0x1b8/0x1fc
...
To fix this, the PL bit-field in RDES3 register is used for all
descriptors, whether it is the last descriptor or not.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix e4b bitmap inconsistency reports
A bitmap inconsistency issue was observed during stress tests under
mixed huge-page workloads. Ext4 reported multiple e4b bitmap check
failures like:
ext4_mb_complex_scan_group:2508: group 350, 8179 free clusters as
per group info. But got 8192 blocks
Analysis and experimentation confirmed that the issue is caused by a
race condition between page migration and bitmap modification. Although
this timing window is extremely narrow, it is still hit in practice:
folio_lock ext4_mb_load_buddy
__migrate_folio
check ref count
folio_mc_copy __filemap_get_folio
folio_try_get(folio)
......
mb_mark_used
ext4_mb_unload_buddy
__folio_migrate_mapping
folio_ref_freeze
folio_unlock
The root cause of this issue is that the fast path of load_buddy only
increments the folio's reference count, which is insufficient to prevent
concurrent folio migration. We observed that the folio migration process
acquires the folio lock. Therefore, we can determine whether to take the
fast path in load_buddy by checking the lock status. If the folio is
locked, we opt for the slow path (which acquires the lock) to close this
concurrency window.
Additionally, this change addresses the following issues:
When the DOUBLE_CHECK macro is enabled to inspect bitmap-related
issues, the following error may be triggered:
corruption in group 324 at byte 784(6272): f in copy != ff on
disk/prealloc
Analysis reveals that this is a false positive. There is a specific race
window where the bitmap and the group descriptor become momentarily
inconsistent, leading to this error report:
ext4_mb_load_buddy ext4_mb_load_buddy
__filemap_get_folio(create|lock)
folio_lock
ext4_mb_init_cache
folio_mark_uptodate
__filemap_get_folio(no lock)
......
mb_mark_used
mb_mark_used_double
mb_cmp_bitmaps
mb_set_bits(e4b->bd_bitmap)
folio_unlock
The original logic assumed that since mb_cmp_bitmaps is called when the
bitmap is newly loaded from disk, the folio lock would be sufficient to
prevent concurrent access. However, this overlooks a specific race
condition: if another process attempts to load buddy and finds the folio
is already in an uptodate state, it will immediately begin using it without
holding folio lock.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
iommu/vt-d: Clear Present bit before tearing down context entry
When tearing down a context entry, the current implementation zeros the
entire 128-bit entry using multiple 64-bit writes. This creates a window
where the hardware can fetch a "torn" entry — where some fields are
already zeroed while the 'Present' bit is still set — leading to
unpredictable behavior or spurious faults.
While x86 provides strong write ordering, the compiler may reorder writes
to the two 64-bit halves of the context entry. Even without compiler
reordering, the hardware fetch is not guaranteed to be atomic with
respect to multiple CPU writes.
Align with the "Guidance to Software for Invalidations" in the VT-d spec
(Section 6.5.3.3) by implementing the recommended ownership handshake:
1. Clear only the 'Present' (P) bit of the context entry first to
signal the transition of ownership from hardware to software.
2. Use dma_wmb() to ensure the cleared bit is visible to the IOMMU.
3. Perform the required cache and context-cache invalidation to ensure
hardware no longer has cached references to the entry.
4. Fully zero out the entry only after the invalidation is complete.
Also, add a dma_wmb() to context_set_present() to ensure the entry
is fully initialized before the 'Present' bit becomes visible.
CVSS Score
7.5
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix EEXIST abort due to non-consecutive gaps in chunk allocation
I have been observing a number of systems aborting at
insert_dev_extents() in btrfs_create_pending_block_groups(). The
following is a sample stack trace of such an abort coming from forced
chunk allocation (typically behind CONFIG_BTRFS_EXPERIMENTAL) but this
can theoretically happen to any DUP chunk allocation.
[81.801] ------------[ cut here ]------------
[81.801] BTRFS: Transaction aborted (error -17)
[81.801] WARNING: fs/btrfs/block-group.c:2876 at btrfs_create_pending_block_groups+0x721/0x770 [btrfs], CPU#1: bash/319
[81.802] Modules linked in: virtio_net btrfs xor zstd_compress raid6_pq null_blk
[81.803] CPU: 1 UID: 0 PID: 319 Comm: bash Kdump: loaded Not tainted 6.19.0-rc6+ #319 NONE
[81.803] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014
[81.804] RIP: 0010:btrfs_create_pending_block_groups+0x723/0x770 [btrfs]
[81.806] RSP: 0018:ffffa36241a6bce8 EFLAGS: 00010282
[81.806] RAX: 000000000000000d RBX: ffff8e699921e400 RCX: 0000000000000000
[81.807] RDX: 0000000002040001 RSI: 00000000ffffffef RDI: ffffffffc0608bf0
[81.807] RBP: 00000000ffffffef R08: ffff8e69830f6000 R09: 0000000000000007
[81.808] R10: ffff8e699921e5e8 R11: 0000000000000000 R12: ffff8e6999228000
[81.808] R13: ffff8e6984d82000 R14: ffff8e69966a69c0 R15: ffff8e69aa47b000
[81.809] FS: 00007fec6bdd9740(0000) GS:ffff8e6b1b379000(0000) knlGS:0000000000000000
[81.809] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[81.810] CR2: 00005604833670f0 CR3: 0000000116679000 CR4: 00000000000006f0
[81.810] Call Trace:
[81.810] <TASK>
[81.810] __btrfs_end_transaction+0x3e/0x2b0 [btrfs]
[81.811] btrfs_force_chunk_alloc_store+0xcd/0x140 [btrfs]
[81.811] kernfs_fop_write_iter+0x15f/0x240
[81.812] vfs_write+0x264/0x500
[81.812] ksys_write+0x6c/0xe0
[81.812] do_syscall_64+0x66/0x770
[81.812] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[81.813] RIP: 0033:0x7fec6be66197
[81.814] RSP: 002b:00007fffb159dd30 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
[81.815] RAX: ffffffffffffffda RBX: 00007fec6bdd9740 RCX: 00007fec6be66197
[81.815] RDX: 0000000000000002 RSI: 0000560483374f80 RDI: 0000000000000001
[81.816] RBP: 0000560483374f80 R08: 0000000000000000 R09: 0000000000000000
[81.816] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000002
[81.817] R13: 00007fec6bfb85c0 R14: 00007fec6bfb5ee0 R15: 00005604833729c0
[81.817] </TASK>
[81.817] irq event stamp: 20039
[81.818] hardirqs last enabled at (20047): [<ffffffff99a68302>] __up_console_sem+0x52/0x60
[81.818] hardirqs last disabled at (20056): [<ffffffff99a682e7>] __up_console_sem+0x37/0x60
[81.819] softirqs last enabled at (19470): [<ffffffff999d2b46>] __irq_exit_rcu+0x96/0xc0
[81.819] softirqs last disabled at (19463): [<ffffffff999d2b46>] __irq_exit_rcu+0x96/0xc0
[81.820] ---[ end trace 0000000000000000 ]---
[81.820] BTRFS: error (device dm-7 state A) in btrfs_create_pending_block_groups:2876: errno=-17 Object already exists
Inspecting these aborts with drgn, I observed a pattern of overlapping
chunk_maps. Note how stripe 1 of the first chunk overlaps in physical
address with stripe 0 of the second chunk.
Physical Start Physical End Length Logical Type Stripe
----------------------------------------------------------------------------------------------------
0x0000000102500000 0x0000000142500000 1.0G 0x0000000641d00000 META|DUP 0/2
0x0000000142500000 0x0000000182500000 1.0G 0x0000000641d00000 META|DUP 1/2
0x0000000142500000 0x0000000182500000 1.0G 0x0000000601d00000 META|DUP 0/2
0x0000000182500000 0x00000001c2500000 1.0G 0x0000000601d00000 META|DUP 1/2
Now how could this possibly happen? All chunk allocation is
---truncated---
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
net: usb: catc: enable basic endpoint checking
catc_probe() fills three URBs with hardcoded endpoint pipes without
verifying the endpoint descriptors:
- usb_sndbulkpipe(usbdev, 1) and usb_rcvbulkpipe(usbdev, 1) for TX/RX
- usb_rcvintpipe(usbdev, 2) for interrupt status
A malformed USB device can present these endpoints with transfer types
that differ from what the driver assumes.
Add a catc_usb_ep enum for endpoint numbers, replacing magic constants
throughout. Add usb_check_bulk_endpoints() and usb_check_int_endpoints()
calls after usb_set_interface() to verify endpoint types before use,
rejecting devices with mismatched descriptors at probe time.
Similar to
- commit 90b7f2961798 ("net: usb: rtl8150: enable basic endpoint checking")
which fixed the issue in rtl8150.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
ipvs: do not keep dest_dst if dev is going down
There is race between the netdev notifier ip_vs_dst_event()
and the code that caches dst with dev that is going down.
As the FIB can be notified for the closed device after our
handler finishes, it is possible valid route to be returned
and cached resuling in a leaked dev reference until the dest
is not removed.
To prevent new dest_dst to be attached to dest just after the
handler dropped the old one, add a netif_running() check
to make sure the notifier handler is not currently running
for device that is closing.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path
icmp_route_lookup() performs multiple route lookups to find a suitable
route for sending ICMP error messages, with special handling for XFRM
(IPsec) policies.
The lookup sequence is:
1. First, lookup output route for ICMP reply (dst = original src)
2. Pass through xfrm_lookup() for policy check
3. If blocked (-EPERM) or dst is not local, enter "reverse path"
4. In reverse path, call xfrm_decode_session_reverse() to get fl4_dec
which reverses the original packet's flow (saddr<->daddr swapped)
5. If fl4_dec.saddr is local (we are the original destination), use
__ip_route_output_key() for output route lookup
6. If fl4_dec.saddr is NOT local (we are a forwarding node), use
ip_route_input() to simulate the reverse packet's input path
7. Finally, pass rt2 through xfrm_lookup() with XFRM_LOOKUP_ICMP flag
The bug occurs in step 6: ip_route_input() is called with fl4_dec.daddr
(original packet's source) as destination. If this address becomes local
between the initial check and ip_route_input() call (e.g., due to
concurrent "ip addr add"), ip_route_input() returns a LOCAL route with
dst.output set to ip_rt_bug.
This route is then used for ICMP output, causing dst_output() to call
ip_rt_bug(), triggering a WARN_ON:
------------[ cut here ]------------
WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x21/0x30, CPU#1
Call Trace:
<TASK>
ip_push_pending_frames+0x202/0x240
icmp_push_reply+0x30d/0x430
__icmp_send+0x1149/0x24f0
ip_options_compile+0xa2/0xd0
ip_rcv_finish_core+0x829/0x1950
ip_rcv+0x2d7/0x420
__netif_receive_skb_one_core+0x185/0x1f0
netif_receive_skb+0x90/0x450
tun_get_user+0x3413/0x3fb0
tun_chr_write_iter+0xe4/0x220
...
Fix this by checking rt2->rt_type after ip_route_input(). If it's
RTN_LOCAL, the route cannot be used for output, so treat it as an error.
The reproducer requires kernel modification to widen the race window,
making it unsuitable as a selftest. It is available at:
https://gist.github.com/mrpre/eae853b72ac6a750f5d45d64ddac1e81
CVSS Score
4.7
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
apparmor: Fix & Optimize table creation from possibly unaligned memory
Source blob may come from userspace and might be unaligned.
Try to optize the copying process by avoiding unaligned memory accesses.
- Added Fixes tag
- Added "Fix &" to description as this doesn't just optimize but fixes
a potential unaligned memory access
[jj: remove duplicate word "convert" in comment trigger checkpatch warning]
CVSS Score
7.1
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
iommu/vt-d: Clear Present bit before tearing down PASID entry
The Intel VT-d Scalable Mode PASID table entry consists of 512 bits (64
bytes). When tearing down an entry, the current implementation zeros the
entire 64-byte structure immediately using multiple 64-bit writes.
Since the IOMMU hardware may fetch these 64 bytes using multiple
internal transactions (e.g., four 128-bit bursts), updating or zeroing
the entire entry while it is active (P=1) risks a "torn" read. If a
hardware fetch occurs simultaneously with the CPU zeroing the entry, the
hardware could observe an inconsistent state, leading to unpredictable
behavior or spurious faults.
Follow the "Guidance to Software for Invalidations" in the VT-d spec
(Section 6.5.3.3) by implementing the recommended ownership handshake:
1. Clear only the 'Present' (P) bit of the PASID entry.
2. Use a dma_wmb() to ensure the cleared bit is visible to hardware
before proceeding.
3. Execute the required invalidation sequence (PASID cache, IOTLB, and
Device-TLB flush) to ensure the hardware has released all cached
references.
4. Only after the flushes are complete, zero out the remaining fields
of the PASID entry.
Also, add a dma_wmb() in pasid_set_present() to ensure that all other
fields of the PASID entry are visible to the hardware before the Present
bit is set.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-27