Linux: >> Linux Kernel >> 6.1.121 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
net/rds: Fix circular locking dependency in rds_tcp_tune
syzbot reported a circular locking dependency in rds_tcp_tune() where
sk_net_refcnt_upgrade() is called while holding the socket lock:
======================================================
WARNING: possible circular locking dependency detected
======================================================
kworker/u10:8/15040 is trying to acquire lock:
ffffffff8e9aaf80 (fs_reclaim){+.+.}-{0:0},
at: __kmalloc_cache_noprof+0x4b/0x6f0
but task is already holding lock:
ffff88805a3c1ce0 (k-sk_lock-AF_INET6){+.+.}-{0:0},
at: rds_tcp_tune+0xd7/0x930
The issue occurs because sk_net_refcnt_upgrade() performs memory
allocation (via get_net_track() -> ref_tracker_alloc()) while the
socket lock is held, creating a circular dependency with fs_reclaim.
Fix this by moving sk_net_refcnt_upgrade() outside the socket lock
critical section. This is safe because the fields modified by the
sk_net_refcnt_upgrade() call (sk_net_refcnt, ns_tracker) are not
accessed by any concurrent code path at this point.
v2:
- Corrected fixes tag
- check patch line wrap nits
- ai commentary nits
CVSS Score
7.5
EPSS Score
0.0
Published
2026-04-03
In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix race on rawdata dereference
There is a race condition that leads to a use-after-free situation:
because the rawdata inodes are not refcounted, an attacker can start
open()ing one of the rawdata files, and at the same time remove the
last reference to this rawdata (by removing the corresponding profile,
for example), which frees its struct aa_loaddata; as a result, when
seq_rawdata_open() is reached, i_private is a dangling pointer and
freed memory is accessed.
The rawdata inodes weren't refcounted to avoid a circular refcount and
were supposed to be held by the profile rawdata reference. However
during profile removal there is a window where the vfs and profile
destruction race, resulting in the use after free.
Fix this by moving to a double refcount scheme. Where the profile
refcount on rawdata is used to break the circular dependency. Allowing
for freeing of the rawdata once all inode references to the rawdata
are put.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix race between freeing data and fs accessing it
AppArmor was putting the reference to i_private data on its end after
removing the original entry from the file system. However the inode
can aand does live beyond that point and it is possible that some of
the fs call back functions will be invoked after the reference has
been put, which results in a race between freeing the data and
accessing it through the fs.
While the rawdata/loaddata is the most likely candidate to fail the
race, as it has the fewest references. If properly crafted it might be
possible to trigger a race for the other types stored in i_private.
Fix this by moving the put of i_private referenced data to the correct
place which is during inode eviction.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix: limit the number of levels of policy namespaces
Currently the number of policy namespaces is not bounded relying on
the user namespace limit. However policy namespaces aren't strictly
tied to user namespaces and it is possible to create them and nest
them arbitrarily deep which can be used to exhaust system resource.
Hard cap policy namespaces to the same depth as user namespaces.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix side-effect bug in match_char() macro usage
The match_char() macro evaluates its character parameter multiple
times when traversing differential encoding chains. When invoked
with *str++, the string pointer advances on each iteration of the
inner do-while loop, causing the DFA to check different characters
at each iteration and therefore skip input characters.
This results in out-of-bounds reads when the pointer advances past
the input buffer boundary.
[ 94.984676] ==================================================================
[ 94.985301] BUG: KASAN: slab-out-of-bounds in aa_dfa_match+0x5ae/0x760
[ 94.985655] Read of size 1 at addr ffff888100342000 by task file/976
[ 94.986319] CPU: 7 UID: 1000 PID: 976 Comm: file Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy)
[ 94.986322] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 94.986329] Call Trace:
[ 94.986341] <TASK>
[ 94.986347] dump_stack_lvl+0x5e/0x80
[ 94.986374] print_report+0xc8/0x270
[ 94.986384] ? aa_dfa_match+0x5ae/0x760
[ 94.986388] kasan_report+0x118/0x150
[ 94.986401] ? aa_dfa_match+0x5ae/0x760
[ 94.986405] aa_dfa_match+0x5ae/0x760
[ 94.986408] __aa_path_perm+0x131/0x400
[ 94.986418] aa_path_perm+0x219/0x2f0
[ 94.986424] apparmor_file_open+0x345/0x570
[ 94.986431] security_file_open+0x5c/0x140
[ 94.986442] do_dentry_open+0x2f6/0x1120
[ 94.986450] vfs_open+0x38/0x2b0
[ 94.986453] ? may_open+0x1e2/0x2b0
[ 94.986466] path_openat+0x231b/0x2b30
[ 94.986469] ? __x64_sys_openat+0xf8/0x130
[ 94.986477] do_file_open+0x19d/0x360
[ 94.986487] do_sys_openat2+0x98/0x100
[ 94.986491] __x64_sys_openat+0xf8/0x130
[ 94.986499] do_syscall_64+0x8e/0x660
[ 94.986515] ? count_memcg_events+0x15f/0x3c0
[ 94.986526] ? srso_alias_return_thunk+0x5/0xfbef5
[ 94.986540] ? handle_mm_fault+0x1639/0x1ef0
[ 94.986551] ? vma_start_read+0xf0/0x320
[ 94.986558] ? srso_alias_return_thunk+0x5/0xfbef5
[ 94.986561] ? srso_alias_return_thunk+0x5/0xfbef5
[ 94.986563] ? fpregs_assert_state_consistent+0x50/0xe0
[ 94.986572] ? srso_alias_return_thunk+0x5/0xfbef5
[ 94.986574] ? arch_exit_to_user_mode_prepare+0x9/0xb0
[ 94.986587] ? srso_alias_return_thunk+0x5/0xfbef5
[ 94.986588] ? irqentry_exit+0x3c/0x590
[ 94.986595] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 94.986597] RIP: 0033:0x7fda4a79c3ea
Fix by extracting the character value before invoking match_char,
ensuring single evaluation per outer loop.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix missing bounds check on DEFAULT table in verify_dfa()
The verify_dfa() function only checks DEFAULT_TABLE bounds when the state
is not differentially encoded.
When the verification loop traverses the differential encoding chain,
it reads k = DEFAULT_TABLE[j] and uses k as an array index without
validation. A malformed DFA with DEFAULT_TABLE[j] >= state_count,
therefore, causes both out-of-bounds reads and writes.
[ 57.179855] ==================================================================
[ 57.180549] BUG: KASAN: slab-out-of-bounds in verify_dfa+0x59a/0x660
[ 57.180904] Read of size 4 at addr ffff888100eadec4 by task su/993
[ 57.181554] CPU: 1 UID: 0 PID: 993 Comm: su Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy)
[ 57.181558] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 57.181563] Call Trace:
[ 57.181572] <TASK>
[ 57.181577] dump_stack_lvl+0x5e/0x80
[ 57.181596] print_report+0xc8/0x270
[ 57.181605] ? verify_dfa+0x59a/0x660
[ 57.181608] kasan_report+0x118/0x150
[ 57.181620] ? verify_dfa+0x59a/0x660
[ 57.181623] verify_dfa+0x59a/0x660
[ 57.181627] aa_dfa_unpack+0x1610/0x1740
[ 57.181629] ? __kmalloc_cache_noprof+0x1d0/0x470
[ 57.181640] unpack_pdb+0x86d/0x46b0
[ 57.181647] ? srso_alias_return_thunk+0x5/0xfbef5
[ 57.181653] ? srso_alias_return_thunk+0x5/0xfbef5
[ 57.181656] ? aa_unpack_nameX+0x1a8/0x300
[ 57.181659] aa_unpack+0x20b0/0x4c30
[ 57.181662] ? srso_alias_return_thunk+0x5/0xfbef5
[ 57.181664] ? stack_depot_save_flags+0x33/0x700
[ 57.181681] ? kasan_save_track+0x4f/0x80
[ 57.181683] ? kasan_save_track+0x3e/0x80
[ 57.181686] ? __kasan_kmalloc+0x93/0xb0
[ 57.181688] ? __kvmalloc_node_noprof+0x44a/0x780
[ 57.181693] ? aa_simple_write_to_buffer+0x54/0x130
[ 57.181697] ? policy_update+0x154/0x330
[ 57.181704] aa_replace_profiles+0x15a/0x1dd0
[ 57.181707] ? srso_alias_return_thunk+0x5/0xfbef5
[ 57.181710] ? __kvmalloc_node_noprof+0x44a/0x780
[ 57.181712] ? aa_loaddata_alloc+0x77/0x140
[ 57.181715] ? srso_alias_return_thunk+0x5/0xfbef5
[ 57.181717] ? _copy_from_user+0x2a/0x70
[ 57.181730] policy_update+0x17a/0x330
[ 57.181733] profile_replace+0x153/0x1a0
[ 57.181735] ? rw_verify_area+0x93/0x2d0
[ 57.181740] vfs_write+0x235/0xab0
[ 57.181745] ksys_write+0xb0/0x170
[ 57.181748] do_syscall_64+0x8e/0x660
[ 57.181762] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 57.181765] RIP: 0033:0x7f6192792eb2
Remove the MATCH_FLAG_DIFF_ENCODE condition to validate all DEFAULT_TABLE
entries unconditionally.
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
apparmor: Fix double free of ns_name in aa_replace_profiles()
if ns_name is NULL after
1071 error = aa_unpack(udata, &lh, &ns_name);
and if ent->ns_name contains an ns_name in
1089 } else if (ent->ns_name) {
then ns_name is assigned the ent->ns_name
1095 ns_name = ent->ns_name;
however ent->ns_name is freed at
1262 aa_load_ent_free(ent);
and then again when freeing ns_name at
1270 kfree(ns_name);
Fix this by NULLing out ent->ns_name after it is transferred to ns_name
")
CVSS Score
7.8
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix differential encoding verification
Differential encoding allows loops to be created if it is abused. To
prevent this the unpack should verify that a diff-encode chain
terminates.
Unfortunately the differential encode verification had two bugs.
1. it conflated states that had gone through check and already been
marked, with states that were currently being checked and marked.
This means that loops in the current chain being verified are treated
as a chain that has already been verified.
2. the order bailout on already checked states compared current chain
check iterators j,k instead of using the outer loop iterator i.
Meaning a step backwards in states in the current chain verification
was being mistaken for moving to an already verified state.
Move to a double mark scheme where already verified states get a
different mark, than the current chain being kept. This enables us
to also drop the backwards verification check that was the cause of
the second error as any already verified state is already marked.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE
When installing an emulated MMIO SPTE, do so *after* dropping/zapping the
existing SPTE (if it's shadow-present). While commit a54aa15c6bda3 was
right about it being impossible to convert a shadow-present SPTE to an
MMIO SPTE due to a _guest_ write, it failed to account for writes to guest
memory that are outside the scope of KVM.
E.g. if host userspace modifies a shadowed gPTE to switch from a memslot
to emulted MMIO and then the guest hits a relevant page fault, KVM will
install the MMIO SPTE without first zapping the shadow-present SPTE.
------------[ cut here ]------------
is_shadow_present_pte(*sptep)
WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292
Modules linked in: kvm_intel kvm irqbypass
CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm]
Call Trace:
<TASK>
mmu_set_spte+0x237/0x440 [kvm]
ept_page_fault+0x535/0x7f0 [kvm]
kvm_mmu_do_page_fault+0xee/0x1f0 [kvm]
kvm_mmu_page_fault+0x8d/0x620 [kvm]
vmx_handle_exit+0x18c/0x5a0 [kvm_intel]
kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm]
kvm_vcpu_ioctl+0x2d5/0x980 [kvm]
__x64_sys_ioctl+0x8a/0xd0
do_syscall_64+0xb5/0x730
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x47fa3f
</TASK>
---[ end trace 0000000000000000 ]---
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-01
In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix memory leak in verify_header
The function sets `*ns = NULL` on every call, leaking the namespace
string allocated in previous iterations when multiple profiles are
unpacked. This also breaks namespace consistency checking since *ns
is always NULL when the comparison is made.
Remove the incorrect assignment.
The caller (aa_unpack) initializes *ns to NULL once before the loop,
which is sufficient.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-04-01