Linux: >> Linux Kernel >> 6.3.6 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
mm/damon/sysfs-schemes: call missing mem_cgroup_iter_break()
damon_sysfs_memcg_path_to_id() breaks mem_cgroup_iter() loop without
calling mem_cgroup_iter_break(). This leaks the cgroup reference. Fix
the issue by calling mem_cgroup_iter_break() before the break.
The issue was discovered [1] by Sashiko.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: tp_meter: directly shut down timer on cleanup
batadv_tp_sender_cleanup() was calling timer_delete_sync() followed by
timer_delete() to guard against the timer handler re-arming itself between
the two calls. This double-deletion hack relied on the sending status being
set to 0 to suppress re-arming.
Replace both calls with a single timer_shutdown_sync(). This function both
waits for any running timer callback to complete (like timer_delete_sync())
and permanently disarms the timer so it cannot be re-armed afterwards,
making re-arming prevention unconditional and self-documenting.
The re-arming property is also required because otherwise:
1. context 0 (batadv_tp_recv_ack()) checks in
batadv_tp_reset_sender_timer() if sending is still 1 -> it is
2. context 1 changes in batadv_tp_sender_shutdown() sending to 0 and in
this process forces the kthread to stop timer in
batadv_tp_sender_cleanup()
3. context 0 continues in batadv_tp_reset_sender_timer() and rearms the
timer -> but the reference for it is already gone
CVSS Score
8.8
EPSS Score
0.003
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: bla: avoid NULL-ptr deref for claim via dropped interface
Without rtnl_lock held, a hardif might be retrieved as primary interface of
a meshif, but then (while operating on this interface) getting decoupled
from the mesh interface. In this case, the meshif still exists but the
pointer from the primary hardif to the meshif is set to NULL.
The mesh_iface must be checked first to be non-NULL before continuing to
send an ARP request using meshif.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: bla: avoid double decrement of bla.num_requests
The bla.num_requests is increased when no request_sent was in progress. And
it is decremented in various places (announcement was received, backbone is
purged, periodic work). But the check if the request_sent is actually set
to a specific state and the atomic_dec/_inc are not safe because they are
not atomic (TOCTOU) and multiple such code portions can run concurrently.
At the same time, it is necessary to modify request_sent (state) and
bla.num_requests atomically. Otherwise batadv_bla_send_request() might set
request_sent to 1 and is interrupted. batadv_handle_announce() can then
set request_sent back to 0 and decrement num_requests before
batadv_bla_send_request() incremented it.
The two operations must therefore be locked. And since state (request_sent)
and wait_periods are only accessed inside this lock, they can be converted
to simpler datatypes. And to avoid that the bla.num_requests is touched by
a parallel running context with a valid backbone_gw reference after
batadv_bla_purge_backbone_gw() ran, a third state "stopped" is required to
correctly signal that a backbone_gw is in the state of being cleaned up.
CVSS Score
7.1
EPSS Score
0.003
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: tt: avoid empty VLAN responses
The commit 16116dac2339 ("batman-adv: prevent TT request storms by not
sending inconsistent TT TLVLs") added checks to the local (direct) TT
response code. But the response can also be done indirectly by another node
using the global TT state. To avoid such inconsistency states reported in
the original fix, also avoid sending empty VLANs for replies from the
global TT state.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: tt: fix TOCTOU race for reported vlans
The local TT based TVLV is generated by first checking the number of VLANs
which have at least one TT entry. A new buffer with the correct size for
the VLANs is then allocated. Only then, the list of VLANs s used to fill
the VLAN entries in the buffer. During this time, the meshif_vlan_list_lock
is held. But the actual number of TT entries of each VLAN can still
increase during this time - just not the number of VLANs in the list.
But the prefilter used in the buffer size calculation might still cause an
increase of the number of VLANs which need to be stored. Simply because a
VLAN might now suddenly have at least one entry when it had none in the
pre-alloc check - and then needs to occupy space which was not allocated.
It is better to overestimate the buffer size at the beginning and then fill
the buffer only with the VLANs which are not empty.
CVSS Score
9.8
EPSS Score
0.006
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
crypto: nx - fix nx_crypto_ctx_exit argument
nx_crypto_ctx_shash_exit calls nx_crypto_ctx_exit with crypto_shash_ctx(...)
but crypto_shash_ctx gives a nx_crypto_ctx *, not a crypto_tfm *.
Fix the type in nx_crypto_ctx_exit and drop the bogus crypto_tfm_ctx
call.
This fixes the following oops:
BUG: Unable to handle kernel data access at 0xc0403effffffffc8
Faulting instruction address: 0xc000000000396cb4
Oops: Kernel access of bad area, sig: 11 [#15]
Call Trace:
nx_crypto_ctx_shash_exit+0x24/0x60
crypto_shash_exit_tfm+0x28/0x40
crypto_destroy_tfm+0x98/0x140
crypto_exit_ahash_using_shash+0x20/0x40
crypto_destroy_tfm+0x98/0x140
hash_release+0x1c/0x30
alg_sock_destruct+0x38/0x60
__sk_destruct+0x48/0x2b0
af_alg_release+0x58/0xb0
__sock_release+0x68/0x150
sock_close+0x20/0x40
__fput+0x110/0x3a0
sys_close+0x48/0xa0
system_call_exception+0x140/0x2d0
system_call_common+0xf4/0x258
.. which came from hardlink(1) opportunistically using AF_ALG.
The same problem exists with nx_crypto_ctx_skcipher_exit getting a context
it wasn't expecting, but apparently nobody hit that for years.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
KVM: Replace guest-triggerable BUG_ON() in ioeventfd datamatch with get_unaligned()
Drop a BUG_ON() that has been reachable since it was first added, way back
in 2009, and instead use get_unaligned() to perform potentially-unaligned
accesses.
For a given store, KVM x86's emulator tracks the entire value in the
destination operand, x86_emulate_ctxt.dst. If the destination is memory,
and the target splits multiple pages and/or is emulated MMIO, then KVM
handles each fragment independently. E.g. on a page split starting at page
offset 0xffc, KVM writes 4 bytes to the first page, then the remaining
bytes to the second page, using ctxt->dst as the source for both (with
appropriate offsets).
If the destination splits a page *and* hits emulated MMIO on the second
page, then KVM will complete the write to the first page, then emulate the
MMIO access to the second page. If there is a datamatch-enabled ioeventfd
at offset 0 of the second page, then KVM will process the remainder of the
store as a potential ioeventfd signal.
Putting it all together, if the guest emits a store that splits a page
starting at page offset N, and the second page has a datamatch-enabled
ioeventfd at offset 0, then KVM will check for datamatch using
&dst.valptr[N] as the source. Due to dst (and thus dst.valptr) being
32-byte aligned, if N is not aligned to @len, the BUG_ON() fires.
E.g. with a 16-byte store at page offset 0xffc, to an ioeventfd of len 8,
all initial checks in ioeventfd_in_range() will succeed, and the BUG_ON()
fires due to @val being 4-byte aligned, but not 8-byte aligned.
------------[ cut here ]------------
kernel BUG at arch/x86/kvm/../../../virt/kvm/eventfd.c:783!
Oops: invalid opcode: 0000 [#1] SMP
CPU: 0 UID: 1000 PID: 615 Comm: repro Not tainted 7.1.0-rc2-ff238429d1ea #365 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:ioeventfd_write+0x6c/0x70 [kvm]
Call Trace:
<TASK>
__kvm_io_bus_write+0x85/0xb0 [kvm]
kvm_io_bus_write+0x53/0x80 [kvm]
vcpu_mmio_write+0x66/0xf0 [kvm]
emulator_read_write_onepage+0x12a/0x540 [kvm]
emulator_read_write+0x109/0x2b0 [kvm]
x86_emulate_insn+0x4f8/0xfb0 [kvm]
x86_emulate_instruction+0x181/0x790 [kvm]
kvm_mmu_page_fault+0x313/0x630 [kvm]
vmx_handle_exit+0x18a/0x590 [kvm_intel]
kvm_arch_vcpu_ioctl_run+0xc81/0x1c90 [kvm]
kvm_vcpu_ioctl+0x2d5/0x970 [kvm]
__x64_sys_ioctl+0x8a/0xd0
do_syscall_64+0xb7/0x890
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7f19c931a9bf
</TASK>
Modules linked in: kvm_intel kvm irqbypass
---[ end trace 0000000000000000 ]---
In a perfect world, the fix would be to simply delete the BUG_ON(), as KVM
x86 doesn't perform alignment checks on "normal" memory accesses at CPL0.
Sadly, C99 ruins all the fun; while the x86 architecture plays nice,
dereferencing an unaligned pointer directly is undefined behavior in C,
e.g. triggers splats when running with CONFIG_UBSAN_ALIGNMENT=y.
CVSS Score
7.1
EPSS Score
0.002
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86/mmu: Ensure hugepage is in by slot before checking max mapping level
When recovering hugepages in the shadow MMU, verify that the base gfn of
the shadow page is actually contained within the target memslot, *before*
querying the max mapping level given the shadow page's gfn. Failure to
pre-check the validity of the gfn can lead to an out-of-bounds access to
the slot's lpage_info (which typically manifests as a host #PF because the
lpage_info is vmalloc'd) if the guest creates a hugepage mapping (in its
PTEs) that extends "below" the bounds of a memslot.
When faulting in memory for a guest, and the size of the guest mapping is
greater than KVM's (current) max mapping, then KVM will create a "direct"
shadow page (direct in that there are no gPTEs to shadow, and so the target
gfn is a direct calculation given the base gfn of the shadow page). The
hugepage recovery flow looks for such direct shadow pages, as forcing 4KiB
mappings when dirty logging generates the guest > host mapping size case.
When the 4KiB restriction is lifted, then KVM can replace the shadow page
with a hugepage.
But if KVM originally used a smaller mapping than the guest because the
range of memory covered by the guest hugepage exceeds the bounds of a
memslot, then KVM will link a direct shadow page with a gfn that is outside
the bounds of the memslot being used to fault in memory. The rmap entry
added for the leaf mapping is correct and within bounds, but the gfn of the
leaf SPTE's parent shadow page will be out of bounds.
BUG: unable to handle page fault for address: ffffc90000806ffc
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 100000067 P4D 100000067 PUD 1002a7067 PMD 10612f067 PTE 0
Oops: Oops: 0000 [#1] SMP
CPU: 13 UID: 1000 PID: 757 Comm: mmu_stress_test Not tainted 7.1.0-rc1-48ce1e26eace-x86_pir_to_irr_comments-vm #341 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:kvm_mmu_max_mapping_level+0x79/0x2b0 [kvm]
Call Trace:
<TASK>
kvm_mmu_recover_huge_pages+0x21b/0x320 [kvm]
kvm_set_memslot+0x1ee/0x590 [kvm]
kvm_set_memory_region.part.0+0x3a1/0x4d0 [kvm]
kvm_vm_ioctl+0x9bf/0x15d0 [kvm]
__x64_sys_ioctl+0x8a/0xd0
do_syscall_64+0xb7/0xbb0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7f21c0f1a9bf
</TASK>
Don't bother pre-checking the bounds of the potential hugepage, i.e. don't
check that e.g. sp->gfn + KVM_PAGES_PER_HPAGE(sp->role.level + 1) is also
within the memslot, as the checks performed by kvm_mmu_max_mapping_level()
are a superset of the basic bounds checks. I.e. pre-checking the full
range would be a dubious micro-optimization.
CVSS Score
8.8
EPSS Score
0.001
Published
2026-07-19
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: reject oversized group bitmap descriptors
ocfs2_validate_gd_parent() only bounds bg_bits against the parent
allocator's chain geometry. A malicious descriptor can still claim a
bg_size/bg_bits pair that exceeds the bitmap bytes that physically fit in
the group descriptor block, so later bitmap scans and bit updates can run
past bg_bitmap.
Add a physical-cap check based on ocfs2_group_bitmap_size() for the parent
allocator type and reject descriptors whose bg_size or bg_bits exceed that
capacity. Keep the existing chain geometry check so both the on-disk
bitmap layout and the allocator metadata must agree before the descriptor
is used.
Validation reproduced this kernel report:
KASAN use-after-free in _find_next_bit+0x7f/0xc0
Read of size 8
Call trace:
dump_stack_lvl+0x66/0xa0 (?:?)
print_report+0xd0/0x630 (?:?)
_find_next_bit+0x7f/0xc0 (?:?)
srso_alias_return_thunk+0x5/0xfbef5 (?:?)
__virt_addr_valid+0x188/0x2f0 (?:?)
kasan_report+0xe4/0x120 (?:?)
ocfs2_find_max_contig_free_bits+0x35/0x70 (fs/ocfs2/suballoc.c:1375)
ocfs2_block_group_set_bits+0x472/0x4b0 (fs/ocfs2/suballoc.c:1457)
ocfs2_cluster_group_search+0x16b/0x440 (fs/ocfs2/suballoc.c:86)
ocfs2_bg_discontig_fix_result+0x1ef/0x230 (fs/ocfs2/suballoc.c:1786)
ocfs2_search_chain+0x8f8/0x10a0 (fs/ocfs2/suballoc.c:1886)
get_page_from_freelist+0x70e/0x2370 (?:?)
lock_release+0xc6/0x290 (?:?)
do_raw_spin_unlock+0x9a/0x100 (?:?)
kasan_unpoison+0x27/0x60 (?:?)
__bfs+0x147/0x240 (?:?)
get_page_from_freelist+0x83d/0x2370 (?:?)
ocfs2_claim_suballoc_bits+0x38c/0xe70 (fs/ocfs2/suballoc.c:96)
sched_domains_numa_masks_clear+0x70/0xd0 (?:?)
check_irq_usage+0xe8/0xb70 (?:?)
__ocfs2_claim_clusters+0x18d/0x4c0 (fs/ocfs2/suballoc.c:2497)
check_path+0x24/0x50 (?:?)
rcu_is_watching+0x20/0x50 (?:?)
check_prev_add+0xfd/0xd00 (?:?)
ocfs2_add_clusters_in_btree+0x17d/0x810 (fs/ocfs2/suballoc.c:?)
__folio_batch_add_and_move+0x1f5/0x3d0 (?:?)
ocfs2_add_inode_data+0xd9/0x120 (fs/ocfs2/suballoc.c:?)
filemap_add_folio+0x105/0x1f0 (?:?)
ocfs2_write_begin_nolock+0x29f7/0x2f80 (fs/ocfs2/suballoc.c:3043)
ocfs2_read_inode_block+0xb5/0x110 (fs/ocfs2/suballoc.c:?)
down_write+0xf5/0x180 (?:?)
ocfs2_write_begin+0x180/0x240 (fs/ocfs2/suballoc.c:?)
__mark_inode_dirty+0x758/0x9a0 (?:?)
inode_to_bdi+0x41/0x90 (?:?)
balance_dirty_pages_ratelimited_flags+0xf8/0x1d0 (?:?)
generic_perform_write+0x252/0x440 (?:?)
mnt_put_write_access_file+0x16/0x70 (?:?)
file_update_time_flags+0xe4/0x200 (?:?)
ocfs2_file_write_iter+0x80a/0x1320 (fs/ocfs2/suballoc.c:?)
lock_acquire+0x184/0x2f0 (?:?)
ksys_write+0xd2/0x170 (?:?)
apparmor_file_permission+0xf5/0x310 (?:?)
read_zero+0x8d/0x140 (?:?)
lock_is_held_type+0x8f/0x100 (?:?)
CVSS Score
8.8
EPSS Score
0.005
Published
2026-07-19