Linux: >> Linux Kernel >> 6.1.131 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: prevent rename with empty string
Client can send empty newname string to ksmbd server.
It will cause a kernel oops from d_alloc.
This patch return the error when attempting to rename
a file or directory with an empty new name string.
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
KVM: SVM: Forcibly leave SMM mode on SHUTDOWN interception
Previously, commit ed129ec9057f ("KVM: x86: forcibly leave nested mode
on vCPU reset") addressed an issue where a triple fault occurring in
nested mode could lead to use-after-free scenarios. However, the commit
did not handle the analogous situation for System Management Mode (SMM).
This omission results in triggering a WARN when KVM forces a vCPU INIT
after SHUTDOWN interception while the vCPU is in SMM. This situation was
reprodused using Syzkaller by:
1) Creating a KVM VM and vCPU
2) Sending a KVM_SMI ioctl to explicitly enter SMM
3) Executing invalid instructions causing consecutive exceptions and
eventually a triple fault
The issue manifests as follows:
WARNING: CPU: 0 PID: 25506 at arch/x86/kvm/x86.c:12112
kvm_vcpu_reset+0x1d2/0x1530 arch/x86/kvm/x86.c:12112
Modules linked in:
CPU: 0 PID: 25506 Comm: syz-executor.0 Not tainted
6.1.130-syzkaller-00157-g164fe5dde9b6 #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.12.0-1 04/01/2014
RIP: 0010:kvm_vcpu_reset+0x1d2/0x1530 arch/x86/kvm/x86.c:12112
Call Trace:
<TASK>
shutdown_interception+0x66/0xb0 arch/x86/kvm/svm/svm.c:2136
svm_invoke_exit_handler+0x110/0x530 arch/x86/kvm/svm/svm.c:3395
svm_handle_exit+0x424/0x920 arch/x86/kvm/svm/svm.c:3457
vcpu_enter_guest arch/x86/kvm/x86.c:10959 [inline]
vcpu_run+0x2c43/0x5a90 arch/x86/kvm/x86.c:11062
kvm_arch_vcpu_ioctl_run+0x50f/0x1cf0 arch/x86/kvm/x86.c:11283
kvm_vcpu_ioctl+0x570/0xf00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4122
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
Architecturally, INIT is blocked when the CPU is in SMM, hence KVM's WARN()
in kvm_vcpu_reset() to guard against KVM bugs, e.g. to detect improper
emulation of INIT. SHUTDOWN on SVM is a weird edge case where KVM needs to
do _something_ sane with the VMCB, since it's technically undefined, and
INIT is the least awful choice given KVM's ABI.
So, double down on stuffing INIT on SHUTDOWN, and force the vCPU out of
SMM to avoid any weirdness (and the WARN).
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
[sean: massage changelog, make it clear this isn't architectural behavior]
CVSS Score
7.8
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
net: phy: allow MDIO bus PM ops to start/stop state machine for phylink-controlled PHY
DSA has 2 kinds of drivers:
1. Those who call dsa_switch_suspend() and dsa_switch_resume() from
their device PM ops: qca8k-8xxx, bcm_sf2, microchip ksz
2. Those who don't: all others. The above methods should be optional.
For type 1, dsa_switch_suspend() calls dsa_user_suspend() -> phylink_stop(),
and dsa_switch_resume() calls dsa_user_resume() -> phylink_start().
These seem good candidates for setting mac_managed_pm = true because
that is essentially its definition [1], but that does not seem to be the
biggest problem for now, and is not what this change focuses on.
Talking strictly about the 2nd category of DSA drivers here (which
do not have MAC managed PM, meaning that for their attached PHYs,
mdio_bus_phy_suspend() and mdio_bus_phy_resume() should run in full),
I have noticed that the following warning from mdio_bus_phy_resume() is
triggered:
WARN_ON(phydev->state != PHY_HALTED && phydev->state != PHY_READY &&
phydev->state != PHY_UP);
because the PHY state machine is running.
It's running as a result of a previous dsa_user_open() -> ... ->
phylink_start() -> phy_start() having been initiated by the user.
The previous mdio_bus_phy_suspend() was supposed to have called
phy_stop_machine(), but it didn't. So this is why the PHY is in state
PHY_NOLINK by the time mdio_bus_phy_resume() runs.
mdio_bus_phy_suspend() did not call phy_stop_machine() because for
phylink, the phydev->adjust_link function pointer is NULL. This seems a
technicality introduced by commit fddd91016d16 ("phylib: fix PAL state
machine restart on resume"). That commit was written before phylink
existed, and was intended to avoid crashing with consumer drivers which
don't use the PHY state machine - phylink always does, when using a PHY.
But phylink itself has historically not been developed with
suspend/resume in mind, and apparently not tested too much in that
scenario, allowing this bug to exist unnoticed for so long. Plus, prior
to the WARN_ON(), it would have likely been invisible.
This issue is not in fact restricted to type 2 DSA drivers (according to
the above ad-hoc classification), but can be extrapolated to any MAC
driver with phylink and MDIO-bus-managed PHY PM ops. DSA is just where
the issue was reported. Assuming mac_managed_pm is set correctly, a
quick search indicates the following other drivers might be affected:
$ grep -Zlr PHYLINK_NETDEV drivers/ | xargs -0 grep -L mac_managed_pm
drivers/net/ethernet/atheros/ag71xx.c
drivers/net/ethernet/microchip/sparx5/sparx5_main.c
drivers/net/ethernet/microchip/lan966x/lan966x_main.c
drivers/net/ethernet/freescale/dpaa2/dpaa2-mac.c
drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
drivers/net/ethernet/freescale/ucc_geth.c
drivers/net/ethernet/freescale/enetc/enetc_pf_common.c
drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
drivers/net/ethernet/marvell/mvneta.c
drivers/net/ethernet/marvell/prestera/prestera_main.c
drivers/net/ethernet/mediatek/mtk_eth_soc.c
drivers/net/ethernet/altera/altera_tse_main.c
drivers/net/ethernet/wangxun/txgbe/txgbe_phy.c
drivers/net/ethernet/meta/fbnic/fbnic_phylink.c
drivers/net/ethernet/tehuti/tn40_phy.c
drivers/net/ethernet/mscc/ocelot_net.c
Make the existing conditions dependent on the PHY device having a
phydev->phy_link_change() implementation equal to the default
phy_link_change() provided by phylib. Otherwise, we implicitly know that
the phydev has the phylink-provided phylink_phy_change() callback, and
when phylink is used, the PHY state machine always needs to be stopped/
started on the suspend/resume path. The code is structured as such that
if phydev->phy_link_change() is absent, it is a matter of time until the
kernel will crash - no need to further complicate the test.
Thus, for the situation where the PM is not managed b
---truncated---
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: prevent out-of-bounds stream writes by validating *pos
ksmbd_vfs_stream_write() did not validate whether the write offset
(*pos) was within the bounds of the existing stream data length (v_len).
If *pos was greater than or equal to v_len, this could lead to an
out-of-bounds memory write.
This patch adds a check to ensure *pos is less than v_len before
proceeding. If the condition fails, -EINVAL is returned.
CVSS Score
7.8
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
arm64: bpf: Add BHB mitigation to the epilogue for cBPF programs
A malicious BPF program may manipulate the branch history to influence
what the hardware speculates will happen next.
On exit from a BPF program, emit the BHB mititgation sequence.
This is only applied for 'classic' cBPF programs that are loaded by
seccomp.
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
xenbus: Use kref to track req lifetime
Marek reported seeing a NULL pointer fault in the xenbus_thread
callstack:
BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: e030:__wake_up_common+0x4c/0x180
Call Trace:
<TASK>
__wake_up_common_lock+0x82/0xd0
process_msg+0x18e/0x2f0
xenbus_thread+0x165/0x1c0
process_msg+0x18e is req->cb(req). req->cb is set to xs_wake_up(), a
thin wrapper around wake_up(), or xenbus_dev_queue_reply(). It seems
like it was xs_wake_up() in this case.
It seems like req may have woken up the xs_wait_for_reply(), which
kfree()ed the req. When xenbus_thread resumes, it faults on the zero-ed
data.
Linux Device Drivers 2nd edition states:
"Normally, a wake_up call can cause an immediate reschedule to happen,
meaning that other processes might run before wake_up returns."
... which would match the behaviour observed.
Change to keeping two krefs on each request. One for the caller, and
one for xenbus_thread. Each will kref_put() when finished, and the last
will free it.
This use of kref matches the description in
Documentation/core-api/kref.rst
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
tracing: Verify event formats that have "%*p.."
The trace event verifier checks the formats of trace events to make sure
that they do not point at memory that is not in the trace event itself or
in data that will never be freed. If an event references data that was
allocated when the event triggered and that same data is freed before the
event is read, then the kernel can crash by reading freed memory.
The verifier runs at boot up (or module load) and scans the print formats
of the events and checks their arguments to make sure that dereferenced
pointers are safe. If the format uses "%*p.." the verifier will ignore it,
and that could be dangerous. Cover this case as well.
Also add to the sample code a use case of "%*pbl".
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
ftrace: Add cond_resched() to ftrace_graph_set_hash()
When the kernel contains a large number of functions that can be traced,
the loop in ftrace_graph_set_hash() may take a lot of time to execute.
This may trigger the softlockup watchdog.
Add cond_resched() within the loop to allow the kernel to remain
responsive even when processing a large number of functions.
This matches the cond_resched() that is used in other locations of the
code that iterates over all functions that can be traced.
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
perf/x86/intel: KVM: Mask PEBS_ENABLE loaded for guest with vCPU's value.
When generating the MSR_IA32_PEBS_ENABLE value that will be loaded on
VM-Entry to a KVM guest, mask the value with the vCPU's desired PEBS_ENABLE
value. Consulting only the host kernel's host vs. guest masks results in
running the guest with PEBS enabled even when the guest doesn't want to use
PEBS. Because KVM uses perf events to proxy the guest virtual PMU, simply
looking at exclude_host can't differentiate between events created by host
userspace, and events created by KVM on behalf of the guest.
Running the guest with PEBS unexpectedly enabled typically manifests as
crashes due to a near-infinite stream of #PFs. E.g. if the guest hasn't
written MSR_IA32_DS_AREA, the CPU will hit page faults on address '0' when
trying to record PEBS events.
The issue is most easily reproduced by running `perf kvm top` from before
commit 7b100989b4f6 ("perf evlist: Remove __evlist__add_default") (after
which, `perf kvm top` effectively stopped using PEBS). The userspace side
of perf creates a guest-only PEBS event, which intel_guest_get_msrs()
misconstrues a guest-*owned* PEBS event.
Arguably, this is a userspace bug, as enabling PEBS on guest-only events
simply cannot work, and userspace can kill VMs in many other ways (there
is no danger to the host). However, even if this is considered to be bad
userspace behavior, there's zero downside to perf/KVM restricting PEBS to
guest-owned events.
Note, commit 854250329c02 ("KVM: x86/pmu: Disable guest PEBS temporarily
in two rare situations") fixed the case where host userspace is profiling
KVM *and* userspace, but missed the case where userspace is profiling only
KVM.
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20
In the Linux kernel, the following vulnerability has been resolved:
objtool, media: dib8000: Prevent divide-by-zero in dib8000_set_dds()
If dib8000_set_dds()'s call to dib8000_read32() returns zero, the result
is a divide-by-zero. Prevent that from happening.
Fixes the following warning with an UBSAN kernel:
drivers/media/dvb-frontends/dib8000.o: warning: objtool: dib8000_tune() falls through to next function dib8096p_cfg_DibRx()
CVSS Score
5.5
EPSS Score
0.0
Published
2025-05-20