| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
vsock: treat TCP_CLOSING as once-established
Handle the TCP_ESTABLISHED -> TCP_CLOSING transition on OP_RST, which can
race with the connect loop. Immediately break and return 0 on
ESTABLISHED/CLOSING. The return value of connect() should reflect what
happened up to the point the connection was established or failed. Events
that occur afterwards must not affect it. E.g. even if OP_RW has already
set sk_err, connect() should still return 0, not ENOBUFS because of it.
Adapt the inaccurate comment above signal_pending().
Resetting a socket that is still present in connected_table can lead to
memory corruption. The reporter noted lost transports for in-flight skbs,
and I have reproduced crashes caused by re-insertion into connected_table.
list_add double add: new=, prev=, next=.
kernel BUG at lib/list_debug.c:35!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
Workqueue: vsock-loopback vsock_loopback_work
RIP: 0010:__list_add_valid_or_report+0x11f/0x130
Call Trace:
vsock_insert_connected.cold+0xe/0x13
virtio_transport_recv_pkt+0x10e9/0x1460
vsock_loopback_work+0x305/0x480
process_one_work+0xe4c/0x1560
worker_thread+0x4f1/0xd60
kthread+0x36e/0x470
ret_from_fork+0x47b/0x6b0
ret_from_fork_asm+0x1a/0x30
This fix is supplementary to commit 002541ef650b ("vsock: Ignore
signal/timeout on connect() if already established"). Details under Link. |
| In the Linux kernel, the following vulnerability has been resolved:
net/rds: don't let the rdma_cm destroy an id RDS still owns on route failure
rds_rdma_cm_event_handler_cmn() hands the return value of
rdma_resolve_route() straight back to the rdma_cm on
RDMA_CM_EVENT_ADDR_RESOLVED. A synchronous failure there - -ENOMEM
from the route work allocation, an SA query that cannot be set up, a
RoCE route with no usable device - makes addr_handler() destroy the
id the event was delivered on. That id is ic->i_cm_id, and nothing
clears the pointer: the connection sits in RDS_CONN_CONNECTING with a
freed id until its shutdown calls rdma_disconnect() and
rdma_destroy_id() on it.
The ROUTE_RESOLVED case already avoids this: rds_ib_cm_initiate_connect()
forces a zero return while ic->i_cm_id == cm_id, as the comment there
explains. Do the same here - drop the connection and return 0 - so
the id stays RDS's to destroy from the shutdown, and the reconnect
gets a fresh one. |
| In the Linux kernel, the following vulnerability has been resolved:
netlink: reset skb headers before unicast and multicast filtering
Socket filters can use SKF_NET_OFF and SKF_LL_OFF to read relative to
an skb's network and MAC headers. Netlink producers may reserve
headroom without resetting those headers, allowing a receiving socket's
filter to read data before the initialized message.
For example, IWPM HELLO replies are allocated with dev_alloc_skb(),
which reserves NET_SKB_PAD bytes. An unprivileged NETLINK_RDMA user can
attach a classic socket filter and disclose this headroom through the
length of the delivered reply. The resets in netlink_dump() do not help
because IWPM sends a separately allocated skb through netlink_unicast().
Reset both headers before running the receiver's filter in unicast and
broadcast delivery, as is already done for dump skbs. This also covers
other netlink producers that reserve headroom without changing their
allocation or message-building code. |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: target: iscsi: Fix race in discovery auth updates
Separate configfs opens can concurrently update the discovery AuthMethod
parameter. Both callers may free the same value in
iscsi_update_param_value(), causing a double-free.
Protect the lookup and replacement with the discovery TPG access lock,
as used by the other TPG configfs parameter updates. |
| In the Linux kernel, the following vulnerability has been resolved:
ocfs2/dlm: Protect the recovery list during debugfs reads
Recovery participant records must remain alive while debug_state_print()
walks reco.node_data and formats their fields. The formatter holds
dlm->spinlock, but the recovery participant list is protected by
dlm_reco_state_lock. In particular, dlm_destroy_recovery_area() detaches
the list under dlm_reco_state_lock and frees the detached records after
releasing it. A concurrent debugfs open can therefore read freed memory.
Protect the participant traversal and field reads in debug_state_print()
with dlm_reco_state_lock, matching the existing list writers. This also
serializes the traversal against list_add_tail() during recovery-area
initialization. Make the existing lock available to the debug code
through dlmcommon.h; the lock remains internal to the OCFS2 DLM module.
Release dlm->spinlock after formatting the other domain state and before
acquiring dlm_reco_state_lock, so the debug reader does not nest the two
locks. Leave recovery list insertion, detachment and freeing unchanged.
KASAN report as below:
BUG: KASAN: slab-use-after-free in debug_state_open+0x1169/0x12d0
Read of size 4 at addr ffff88810662ef80 by task dlm-state-stres/896
CPU: 1 UID: 0 PID: 896 Comm: dlm-state-stres Not tainted 7.3.0-rc4-next-20260921-pmb-ocfs2-functional-v1+ #1 PREEMPT(lazy)
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x93/0xd0
print_report+0xce/0x630
? debug_state_open+0x1169/0x12d0
? srso_alias_return_thunk+0x5/0xfbef5
? __virt_addr_valid+0x20e/0x420
? debug_state_open+0x1169/0x12d0
kasan_report+0xe0/0x110
? debug_state_open+0x1169/0x12d0
debug_state_open+0x1169/0x12d0
? __pfx_debug_state_open+0x10/0x10
full_proxy_open_regular+0x193/0x310
do_dentry_open+0x595/0x12d0
? __pfx_full_proxy_open_regular+0x10/0x10
vfs_open_consume+0xd1/0x400
? srso_alias_return_thunk+0x5/0xfbef5
path_openat+0x18d0/0x2020
? __pfx_path_openat+0x10/0x10
do_file_open+0x21e/0x470
? __pfx_do_file_open+0x10/0x10
? _raw_spin_unlock+0x23/0x40
? srso_alias_return_thunk+0x5/0xfbef5
? alloc_fd+0x3a6/0x6b0
do_sys_openat2+0xf4/0x1b0
? __pfx_do_sys_openat2+0x10/0x10
? srso_alias_return_thunk+0x5/0xfbef5
? __fput+0x5b5/0xa60
__x64_sys_openat+0x136/0x1e0
? __pfx___x64_sys_openat+0x10/0x10
do_syscall_64+0x114/0x620
entry_SYSCALL_64_after_hwframe+0x77/0x7f
[Register dump omitted.]
</TASK>
Allocated by task 880:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
__kasan_kmalloc+0xaa/0xb0
__kmalloc_cache_noprof+0x28d/0x610
dlm_remaster_locks+0x147/0x1d90
dlm_do_recovery+0xde1/0x1580
dlm_recovery_thread+0x109/0x300
kthread+0x351/0x460
ret_from_fork+0x659/0x940
ret_from_fork_asm+0x1a/0x30
Freed by task 880:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x5f/0x80
kfree+0x308/0x580
dlm_destroy_recovery_area+0x285/0x460
dlm_remaster_locks+0x17c4/0x1d90
dlm_do_recovery+0xde1/0x1580
dlm_recovery_thread+0x109/0x300
kthread+0x351/0x460
ret_from_fork+0x659/0x940
ret_from_fork_asm+0x1a/0x30
The buggy address belongs to the object at ffff88810662ef80
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
freed 32-byte region [ffff88810662ef80, ffff88810662efa0)
[Page and memory-state dumps omitted.] |
| In the Linux kernel, the following vulnerability has been resolved:
pipe: preserve existing fasync readers on writer setup failure
F_SETFL and FIOASYNC decide whether to invoke ->fasync() before
pipe_fasync() takes pipe->mutex. Two enables of one O_RDWR FIFO can
therefore both enter the callback.
fasync_helper() allocates before checking for an existing entry. If the
first enable installs both entries, a second enable can update the
reader entry and then fail the allocation for the writer entry. The
error path removes the pre-existing reader entry, clearing FASYNC while
the writer entry remains registered. __fput() then skips ->fasync(), so a
later pipe notification can dereference the freed file or its f_owner.
An unprivileged memory-pressure reproducer triggers a KASAN
slab-use-after-free in send_sigio() through this path.
Keep the reader helper's result and undo the registration only if this
call added it. The pipe mutex serializes changes to both lists, so a
failed new registration still removes its reader, while a failed
duplicate preserves the existing registrations and FASYNC. Successful
duplicate enables continue to update fa_fd as before. |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: libsas: Fix SMP IO deadlock during HA resume
smp_execute_task_sg() calls pm_runtime_get_sync() on the host before
issuing an SMP command. When that command is itself issued from the HA
resume path, the get_sync() deadlocks: it waits for the ongoing resume
(the device is RPM_RESUMING), while the resume is blocked in
sas_drain_work() waiting for that same SMP IO to complete.
The deadlock needs an expander-attached SATA disk. During
sas_resume_ha() -> sas_drain_work(), DISCE_RESUME -> sas_resume_sata()
-> ata_sas_port_resume() requests ATA_EH_RESET, and the hard reset for
such a disk is done via SMP PHY CONTROL (sas_ata_hard_reset() ->
sas_phy_reset() -> sas_smp_phy_control() ->
smp_execute_task_sg()). Direct-attached SATA resets through
lldd_control_phy() and SSP devices use TMFs, so neither hits this.
Replace the get_sync()/put_sync() pair with
pm_runtime_get_noresume()/pm_runtime_put(). smp_execute_task_sg() only
needs to hold off autosuspend while the SMP is in flight, and it must
not try to resume the host: a sync resume issued from the HA resume path
itself is what deadlocks, and by the time sas_resume_ha() runs, hw_init
has already reinitialized the hardware, so the device is accessible
without one.
The usage reference is still required. Discovery work normally runs
inside an event worker's PM reference, taken at sas_notify_port_event()
notify time and held until the handler has flushed the disco
queue. sas_rediscover_ex_phy() however requeues DISCE_REVALIDATE_DOMAIN
from within the revalidation worker itself, and flush_workqueue() does
not wait for work items queued during execution, so that chained
revalidation runs with no outer PM reference - without the
get_noresume(), its SMP could race autosuspend.
For the BSG path, sas_smp_handler() is the only caller which may find
the host autosuspended: expander SMP requests do not go through any SCSI
device request queue, so nothing else in that path holds the host
awake. Resume it there with pm_runtime_resume_and_get() and check the
result. |
| In the Linux kernel, the following vulnerability has been resolved:
netlink: avoid hashing the network namespace pointer
The netlink rhashtable key includes a raw struct net pointer and a
user-controlled port ID. Both /proc/net/netlink and socket diagnostics
expose the table's bucket order. By binding and rebinding chosen
NETLINK_USERSOCK port IDs, an unprivileged reader can distinguish equal
buckets and recover the low bits of the Jenkins hash. Its 32-bit seed
and the limited set of kernel-image slides can then be searched offline
to recover the address of init_net.
Use the namespace's unique, non-address net_cookie in the comparison
key instead. It is assigned before the per-net initializers run and
remains unchanged for the namespace's lifetime. The lookup key and
object hash are still built by netlink_compare_arg_init(), keeping
lookup, insertion, removal and rehashing consistent while preserving
namespace separation. Neither public table walker needs to change.
Reading the socket's namespace cookie in netlink_compare() is safe
under RCU, including during namespace teardown. netlink_release()
removes the socket from the hash table and defers its final put with
call_rcu(). cleanup_net() runs the per-net exit methods and waits for
outstanding RCU callbacks with rcu_barrier() before freeing namespace
storage.
Unlike ns.ns_id, net_cookie is also available and initialized during
setup_net() in older stable kernels, making the change straightforward
to backport to v5.15 and later. |
| In the Linux kernel, the following vulnerability has been resolved:
net: bcmgenet: unshare the skb before writing the control block
bcmgenet stores first_cb, last_cb and bytes_sent in the skb control
block and reads them back on completion to free the skb and credit BQL.
ether_setup() leaves IFF_TX_SKB_SHARING set, so the stack can resubmit
a shared skb that is still in the ring. The next transmit overwrites
last_cb, so the earlier slots complete without crediting their bytes
and BQL stalls the queue until the watchdog resets it.
Unshare the skb before writing the control block.
Reproduce with pktgen in clone_skb mode, which hands the driver the same
skb while earlier copies are still in the ring:
modprobe pktgen
pg=/proc/net/pktgen
echo "add_device eth0" > $pg/kpktgend_0
echo "dst_mac AA:BB:CC:DD:EE:FF" > $pg/eth0
echo "dst 192.0.2.1" > $pg/eth0
echo "clone_skb 8" > $pg/eth0
echo "count 0" > $pg/eth0
echo start > $pg/pgctrl &
sleep 5
echo stop > $pg/pgctrl
wait
cat /sys/class/net/eth0/queues/tx-0/byte_queue_limits/inflight
inflight stays nonzero on the now idle queue. clone_skb 0 leaves it at
zero. |
| In the Linux kernel, the following vulnerability has been resolved:
calipso: keep BIG TCP payload_len in calipso_skbuff_setattr()
calipso_skbuff_setattr() adjusts payload_len by the length of the
option it inserts or resizes:
payload = ntohs(ip6_hdr->payload_len);
ip6_hdr->payload_len = htons(payload + len_delta);
GRO can build BIG TCP packets larger than IPV6_MAXPLEN, and stores
payload_len == 0 for them; ipv6_payload_len() then falls back to
skb->len. For such a packet forwarded to a destination mapped to
CALIPSO, the code above writes len_delta (or 65536 + len_delta when
shrinking) into payload_len, and ipv6_payload_len() no longer falls
back to skb->len. nf_tables, conntrack and sch_cake rely on it.
The same arithmetic also wraps when a packet grows past IPV6_MAXPLEN,
and a BIG TCP packet that shrinks below IPV6_MAXPLEN should get its
real length back.
Set payload_len from the skb length with ipv6_set_payload_len(), which
stores 0 above IPV6_MAXPLEN and the real length otherwise, as
ipv6_gro_complete() does. The network header was just reset to
skb->data, so skb->len - sizeof(*ip6_hdr) is the payload length.
Tested on one kernel (arm64, QEMU) with SELinux permissive, a minimal
mdp-generated policy (network_peer_controls=1), "netlabelctl calipso
add pass doi:16" and a NetLabel mapping of fd00:2::/64 to CALIPSO
DOI 16. calipso_skbuff_setattr() was called through
netlbl_skbuff_setattr() from a test-only debugfs hook (not part of
this patch) adding a level-only label; payload_len after the call:
case before fix after fix real length
1000, unlabeled 1016 1016 1016
70000 GSO, payload_len 0 16 0 70016
65530 GSO, grows past MAXPLEN 10 0 65546
65540 GSO with a 24 byte hop
header, shrinks below MAXPLEN 65528 65532 65532
1000 with a 24 byte hop header 992 992 992
(0 means ipv6_payload_len() returns the real length.) On the forward
path, with a client injecting unlabeled UDP through a router to a
server, the router adds the CALIPSO option and the server delivers all
datagrams (Udp6InDatagrams 5, Ip6InTruncatedPkts 0) with this patch. |
| In the Linux kernel, the following vulnerability has been resolved:
gpiolib: fix memory leak in gpiod_set_array_value_complex() on error paths
A drive-by review by Sashiko reports that, after a failed call to
gpiochip_set_multiple(), gpiod_set_array_value() returns abruptly,
bypassing the freeing of possibly alloced bitmaps, potentially leaking
memory. It is an unlikely error path, but is possible.
Defer the return code check until after the bitmap_free() block. |
| In the Linux kernel, the following vulnerability has been resolved:
perf: Fix perf_pmu_migrate_context() leaving events behind
__perf_pmu_remove() walks the group leaders of a CPU and PMU with
perf_event_groups_for_cpu_pmu(), removing each one as it goes.
perf_remove_from_context() takes the leader out of the groups rbtree,
after which rb_next() on that node returns NULL, prematurely ending the
walk. Other groups stay behind in the source context.
On CPU hotplug, they are then torn down with the dying CPU. They keep
running until teardown, while the PMU's interrupt and migrated events
are on a new CPU, which drivers rely on never happening.
Walk ctx->event_list instead and pick out the PMU's events by their
pmu_ctx. |
| In the Linux kernel, the following vulnerability has been resolved:
ASoC: SOF: ipc4-topology: Fix shift-out-of-bounds for aggregated ALH capture
When ch_count is smaller than blob->alh_cfg.device_count (e.g. a mono
capture stream, such as a SmartMic, aggregated across multiple SDW
links), step = ch_count / blob->alh_cfg.device_count truncates to 0.
The subsequent GENMASK(step - 1, 0) then underflows step - 1 (u32) to
UINT_MAX, causing GENMASK()'s internal shift to use an out-of-bounds
exponent:
UBSAN: shift-out-of-bounds in sound/soc/sof/ipc4-topology.c:2363:13
shift exponent 18446744069414584384 is too large for 64-bit type 'long unsigned int'
Treat ch_count < device_count the same way as the existing "channels
equal to output reference channels" case: apply the same ch_mask to
every aggregated device instead of trying to split channels that
can't be evenly divided. |
| In the Linux kernel, the following vulnerability has been resolved:
autofs: ignore notification errors from a replaced pipe
autofs_notify_daemon() takes a reference to the current notification
pipe under wq_mutex, then drops the mutex before writing the request. The
write can block while the daemon enters catatonic mode and installs a
replacement pipe.
If the old pipe's reader is then closed, the delayed write returns -EPIPE
and the generic error path enters catatonic mode again. That transition
acts on the current superblock state, closes the replacement pipe, and
releases the new daemon generation's wait queues.
Only enter catatonic mode when the pipe which failed is still the current
pipe. Factor the already-locked transition so the identity check and state
change are atomic with respect to another replacement.
This was reproduced on v7.3-rc5-337-gff47652a4b66c in a local QEMU guest.
An unprivileged UID 65534 lookup filled the old packet pipe before a
normal CATATONIC/SETPIPEFD restart. On the unmodified kernel, the new pipe
received HUP and both a pending victim lookup and a later lookup failed
with ENOENT in two out of two fresh-mount runs.
With this change, the new pipe remained active, received an intact
304-byte request, and both victim lookups completed in two out of two
runs. Normal lookup and restart-without-a-blocked-writer controls passed.
No KASAN, oops, refcount, or lock diagnostic was observed. A source
reproducer and complete local logs are available privately on request.
The demonstrated impact is limited to denial of a shared autofs service
during a legitimate daemon restart. No memory corruption, information leak,
privilege escalation, or code execution primitive was observed. |
| In the Linux kernel, the following vulnerability has been resolved:
unicode: free the map after a grace period
generic_ci_d_hash() and generic_ci_d_compare() read sb->s_encoding and
dereference the unicode map while a pathwalk in rcu mode holds nothing
but rcu_read_lock(). The filesystems that use them, ext4, f2fs and
tmpfs, drop the map with utf8_unload() from ->put_super(), which runs
when the last reference to the mount goes away. A lookup that is still
inside such a filesystem at that point reads a freed map.
With a pathwalk held up in utf8_casefold_hash() while the last reference
to a casefolded tmpfs goes away:
BUG: KASAN: slab-use-after-free in utf8nlookup+0x74c/0x950
Read of size 8 at addr ff110001030fe658 by task walker/98
Call Trace:
<TASK>
utf8nlookup+0x74c/0x950
utf8byte+0x160/0x1560
utf8_casefold_hash+0x167/0x230
generic_ci_d_hash+0xdd/0x1c0
link_path_walk+0x11ad/0x1d30
path_lookupat+0x63/0xb00
filename_lookup+0x1f1/0x5b0
vfs_statx+0xd7/0x3b0
[...]
Allocated by task 94:
__kmalloc_cache_noprof+0x249/0x560
utf8_load+0x4e/0x570
shmem_parse_opt_casefold.isra.0+0x92/0x270
[...]
Freed by task 97:
kfree+0x1db/0x5b0
shmem_put_super+0x72/0x170
generic_shutdown_super+0x14c/0x530
kill_anon_super+0x3a/0x60
deactivate_locked_super+0x9c/0xf0
cleanup_mnt+0x9f/0x130
So far that has been hard to hit. umount(2) waits for a grace period
in namespace_unlock() before it drops the mount, so only a mount whose
last reference goes away elsewhere, like the close of a file or a chdir
out of a lazily unmounted directory, can race a walker. So it is
reachable.
Delay the free until a grace period has passed. The map and the data
table it holds a reference to then outlive any pathwalk that found the
superblock before the mount went away. The reference on the data table
module is dropped from the rcu callback as well. utf8-core is built in
whenever CONFIG_UNICODE is set, so there is no module exit that would
have to wait for the callbacks.
Overlayfs points the s_encoding of an overlay at the map of its first
layer without taking a reference of its own. That stays correct. The
layer is held by the overlay, so its map is dropped only after the
overlay is gone. |
| In the Linux kernel, the following vulnerability has been resolved:
watch_queue: Fix note pool publication race in watch_queue_set_size()
There is a race between watch_queue_set_size() and post_one_notification().
watch_queue_set_size() publishes wqueue->notes, notes_bitmap, nr_pages and
nr_notes with plain stores, and post_one_notification() reads them with
plain loads under a different lock, so nothing orders the four stores
against the poster's loads: depending on the build, notes can be stored
last (gcc 14 on x86-64 does this). Since keyctl_watch_key() lets a watch
attach to a queue before it is sized, post_one_notification() can already
be running on another CPU at that moment: it reads nr_notes > 0, passes
its bounds check, and then reads notes while it is still NULL,
dereferencing notes[0].
An unprivileged user triggers this reliably by watching one of its own
keys through a notification pipe and racing ioctl(IOC_WATCH_QUEUE_SET_SIZE)
on that pipe against keyctl(KEYCTL_SETPERM) on the key from another CPU,
triggering:
BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:post_one_notification.isra.0+0xa2/0x1e0
Call Trace:
__post_watch_notification+0x148/0x180
keyctl_setperm_key+0x119/0x130
do_syscall_64+0x108/0x4c0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Kernel panic - not syncing: Fatal exception in interrupt
Fix this by publishing nr_notes last with smp_store_release(), and by
reading it once with smp_load_acquire() in post_one_notification() before
the bitmap and the page array are touched. A poster that observes a
non-zero nr_notes then also observes the pool behind it; one that observes
zero drops the notification as before. |
| In the Linux kernel, the following vulnerability has been resolved:
x86/kvm: Don't consume async #PF flags on a kernel #PF in NMI context
An async #PF "page not present" event arrives through the #PF vector,
and its reason sits in the per-CPU apf_reason.flags until
__kvm_handle_async_pf() reads and clears it. If an NMI arrives after
the event is injected and before the #PF handler reads the flags, and
the NMI handler itself takes a #PF, that fault reads and clears the
flags belonging to the #PF it interrupted. It then finds interrupts
disabled in the NMI context it interrupted, and panics:
Kernel panic - not syncing: Host injected async #PF in interrupt
disabled region
Call Trace:
<NMI>
panic+0x52/0x60
__kvm_handle_async_pf+0xb0/0xb0
exc_page_fault+0x71/0xb0
asm_exc_page_fault+0x27/0x30
RIP: 0010:__get_user_nocheck_8+0x6/0x20
perf_callchain_user+0x147/0x1a0
get_perf_callchain+0x12d/0x1c0
...
perf_event_nmi_handler+0x26/0x50
exc_nmi+0xe8/0x110
RIP: 0010:asm_exc_page_fault+0x0/0x30
</NMI>
The last RIP line shows the NMI landing on the first instruction of
the #PF entry. perf with user call chains takes such a fault: the
sampling NMI walks the user stack with __get_user(), which faults when
a saved frame pointer is not a valid user address or the walk runs off
the top of the stack. The same window exists when KVM, running as an
L1 hypervisor with DELIVERY_AS_PF_VMEXIT, reads the flags itself after
a #PF VM-exit.
The NMI entry code saves and restores CR2 for this nesting, but not the
async #PF reason. Andy Lutomirski described the race, with perf as the
example, when async #PF delivery was reworked in 2020 [1]. Saving and
clearing the flags across the NMI, next to CR2, was discussed there but
not merged.
Since that rework, Linux has stopped setting KVM_ASYNC_PF_SEND_ALWAYS,
so the host delivers "page not present" only for user mode faults and
a kernel-mode fault in NMI context (including kernel-mode #MC and #DB)
cannot be an async page fault. In that case, return without touching
the flags so that the interrupted handler finds them intact.
Tested on v7.3-rc5 in a 4-vCPU, 2 GiB guest restored from a snapshot
whose memory is served on demand through userfaultfd, so that reading
it back takes async #PFs, while every thread samples hardware cycles
with user call chains and points its frame pointer at an unmapped page.
Without this patch the guest panicked as above in 3 of 3 runs. With it,
the guest survived 3 of 3 runs of 60 seconds, and the host counted
148,441 to 153,334 kvm_async_pf_not_present events in the first 20
seconds of each. On 6.18.50 the results were the same: the guest
panicked without the patch and survived with it. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: nVMX: Reset MMU back to the root MMU if loading L2 state fails for !VM-Entry
Reset the vCPU's MMU pointer back to the root MMU if loading L2 state fails
in the "not from VM-Entry" case, i.e. when emulating RSM or handling
KVM_SET_NESTED_STATE. Failure to unwind the MMU pointer results in KVM
trying to run L1 with a nested MMU, and is especially problematic if the
vCPU manages to free its nested state before the VM crashes. Constructing
the root for a nested EPT MMU goes through vmcs12, which is dynamically
allocated/freed when nVMX is enabled/disabled. And so if the nested state
is freed with the MMU still pointing at the nested MMU, KVM will hit a NULL
pointer deref when attempting to get L1=>L2 EPTP.
BUG: kernel NULL pointer dereference, address: 0000000000000078
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 114a2d067 P4D 111743067 PUD 11141f067 PMD 0
Oops: Oops: 0000 [#1] SMP
CPU: 20 UID: 1000 PID: 1272 Comm: nested_tdp_faul Not tainted 7.3.0-rc4-8c89f11d1a99b-sink-vm #1914 PREEMPTLAZY
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:nested_ept_get_eptp+0xb/0x10 [kvm_intel]
Call Trace:
<TASK>
kvm_mmu_load+0xcd/0x870 [kvm]
kvm_arch_vcpu_ioctl_run+0x18f5/0x1f80 [kvm]
kvm_vcpu_ioctl+0x2c7/0x970 [kvm]
__x64_sys_ioctl+0x90/0xd0
do_syscall_64+0x9c/0x4d0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x47491b
</TASK>
Modules linked in: kvm_intel kvm irqbypass
CR2: 0000000000000078
---[ end trace 0000000000000000 ]---
RIP: 0010:nested_ept_get_eptp+0xb/0x10 [kvm_intel]
[sean: write changelog] |
| In the Linux kernel, the following vulnerability has been resolved:
fsnotify: prevent mark additions during connector teardown
fsnotify_destroy_marks() keeps a reference to its current mark while it
drops conn->lock to destroy the mark. This stabilizes the forward-walk
cursor, but does not prevent a new mark from being inserted before it.
For example, an inotify watch re-added after IN_IGNORED sorts before the
old, detached mark for the same group. The walk can miss the replacement
and then detach the entire connector from the object.
The replacement is still on its group's marks_list and, for inotify, in
the watch IDR. The group mutex no longer protects the connector's object
from disappearing. An unprivileged fdinfo read racing the final detach
can consequently call igrab(NULL):
BUG: KASAN: null-ptr-deref in igrab+0x24/0x100
Write of size 4 at addr 0000000000000148
Call Trace:
igrab+0x24/0x100
inotify_show_fdinfo+0x1dc/0x5e0
seq_show+0x397/0x690
Set a DESTROYING flag under conn->lock before starting the walk, and
reject new marks on that connector with -ENOENT. The existing add-mark
error paths undo the temporary group-list entry and the backend's watch
allocation. Do not wait for teardown while holding the group mutex,
which the destroyer needs. Once the old connector is detached, an add
can install a fresh connector as before.
This closes the insertion race for all object types using the common
connector teardown, without changing the mark reference or SRCU lifetime
rules. |
| In the Linux kernel, the following vulnerability has been resolved:
ext4: free the sbi after a grace period
ext4_get_link() follows a symlink that keeps its target in a data block
in rcu pathwalk mode with ext4_getblk(EXT4_GET_BLOCKS_CACHED_NOWAIT).
That reads s_mount_state in the ASSERT() of ext4_getblk() and again in
ext4_es_lookup_extent(), and the lookup bumps the extent status hit or
miss counter, all through sb->s_fs_info.
ext4_put_super() destroys those counters, clears sb->s_fs_info and frees
the sbi without waiting for a grace period. A pathwalk that is still in
ext4_get_link() when the last reference to the mount goes away then
dereferences a NULL s_fs_info, the freed sbi or the destroyed percpu
counters.
With a pathwalk held up in ext4_get_link() while the last reference
goes away:
KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af]
RIP: 0010:ext4_getblk+0xf0/0x640
Call Trace:
<TASK>
ext4_get_link+0x26c/0x410
pick_link+0xf96/0x1780
step_into_slowpath+0x9b8/0x1250
path_lookupat+0x484/0xb00
filename_lookup+0x1f1/0x5b0
vfs_statx+0xd7/0x3b0
vfs_fstatat+0x4d/0x90
__do_sys_newfstatat+0xa0/0x100
do_syscall_64+0x10e/0x5e0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
So far that has been hard to hit. umount(2) waits for a grace period in
namespace_unlock() before it drops the mount, so only a mount whose last
reference goes away elsewhere, like the close of a file or a chdir out of
a lazily unmounted directory, can race a walker.
Keep sb->s_fs_info and free the sbi together with the extent status
counters after a grace period. Split the counters out of
ext4_es_unregister_shrinker() for that. The shrinker still gets wasted
in ext4_put_super(), the counters go with the sbi. |
