| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: fix slab-out-of-bounds read in ieee80211_monitor_select_queue()
ieee80211_monitor_select_queue() validates the skb length using skb->len
before dereferencing pointers into skb->data to access the 802.11 header.
However, skb->len includes data in both the linear head buffer and
non-linear fragments/pages. When AF_PACKET sends a packet large enough to
become non-linear, the 802.11 header at skb->data + len_rthdr may extend
past the linear head buffer even though skb->len appears sufficient.
This leads to a slab-out-of-bounds read when accessing hdr->frame_control,
as the kernel reads beyond the allocated skb head buffer:
BUG: KASAN: slab-out-of-bounds in ieee80211_monitor_select_queue+0x1ed/0x220
syzbot has hit the same issues.
Fix this by checking skb_headlen(skb) (which gives the length of the
linear data region) instead of skb->len before dereferencing skb->data
pointers. This ensures the required bytes are actually present in the
linear portion of the skb.
Apply the same fix to ieee80211_validate_radiotap_len() which has the
same class of bug: it uses skb->len to validate accesses to skb->data,
and to the corresponding checks in ieee80211_monitor_start_xmit(): for
drivers advertising NETIF_F_SG the skb is not linearized before
ndo_start_xmit, so the 802.11 header can be read past the linear
buffer there as well. |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix overflow of jump offset in constant blinding
bpf_jit_blind_insn() rewrites 'if rX op imm goto off' into:
AX = imm ^ rnd
AX ^= rnd
if rX op AX goto off
and subtracts 2 from off when the jump is backward. off is s16, so
-32767 and -32768 wrap and the jump goes 32767 insns forward, past the
end of the prog. The jump is inside the patch, hence bpf_adj_branches()
doesn't check it. The kernel crashes when such prog runs with
bpf_jit_harden=2.
Return -ERANGE in such case. bpf_jit_blind_constants() fails the same
way when blinding of other insns moves a jump out of range. |
| In the Linux kernel, the following vulnerability has been resolved:
mm/slab: do not wake up kswapd in __kfree_rcu_sheaf()
Since kfree_rcu() can be called under pi_lock (a raw spinlock in the
scheduler), kfree_rcu() itself should never allocate memory with
__GFP_KSWAPD_RECLAIM as waking up kswapd ends up acquiring pi_lock,
which leads to a deadlock.
Reproducing the issue even intentionally was not straightforward.
The set_cpus_allowed_force() path that is called under pi_lock is
exercised very rarely, and competing tasks that allocate memory will
most likely wake kswapd up.
Therefore the existence of the deadlock was verified with a modified
kernel that has a lockdep map for waking up kswapd:
======================================================
WARNING: possible circular locking dependency detected
7.2.0-rc1-slab-for-next+ #10 Not tainted
------------------------------------------------------
git/6660 is trying to acquire lock:
ffff8e524533c550 (&p->pi_lock){-.-.}-{2:2}, at: _raw_spin_lock_irqsave+0x12/0x20
but task is already holding lock:
ffff8e57bffff1a0 (&pgdat->kswapd_wait){....}-{3:3}, at: _raw_spin_lock_irqsave+0x12/0x20
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&pgdat->kswapd_wait){....}-{3:3}:
__lock_acquire+0x5a4/0xc50
lock_acquire.part.0+0xb7/0x240
lock_acquire+0x70/0x170
__raw_spin_lock_irqsave+0x44/0x80
_raw_spin_lock_irqsave+0x12/0x20
__wake_up_common_lock+0x31/0xa0
__wake_up+0x20/0x40
kswapd_wakeup_wake+0x7e/0x110
wakeup_kswapd+0x295/0x320
wake_all_kswapds+0xac/0x1a0
__alloc_pages_slowpath.constprop.0+0x282/0xf80
__alloc_frozen_pages_noprof+0x32a/0x360
alloc_slab_page+0x2e/0x160
allocate_slab+0x82/0x420
new_slab+0x52/0xb0
refill_objects+0x13d/0x190
refill_sheaf+0x5d/0xd0
__pcs_replace_empty_main+0x230/0xb10
[...]
-> #1 (kswapd_wakeup){-.-.}-{0:0}:
__lock_acquire+0x5a4/0xc50
lock_sync.part.0+0x75/0x100
lock_sync+0x36/0x70
might_wakeup_kswapd+0x61/0xa0
__kfree_rcu_sheaf+0x33/0xd90
kvfree_call_rcu+0x1d4/0x3b0
set_cpus_allowed_force+0x163/0x220
cpuset_cpus_allowed_fallback+0x18b/0x240
select_fallback_rq+0x1e6/0x250
[...]
-> #0 (&p->pi_lock){-.-.}-{2:2}:
check_prev_add+0xe6/0xe00
validate_chain+0x51e/0x6e0
__lock_acquire+0x5a4/0xc50
lock_acquire.part.0+0xb7/0x240
lock_acquire+0x70/0x170
__raw_spin_lock_irqsave+0x44/0x80
_raw_spin_lock_irqsave+0x12/0x20
try_to_wake_up+0x77/0xa90
default_wake_function+0x27/0x60
autoremove_wake_function+0x23/0xb0
__wake_up_common+0xb8/0x170
__wake_up_common_lock+0x51/0xa0
__wake_up+0x20/0x40
kswapd_wakeup_wake+0x7e/0x110
wakeup_kswapd+0x295/0x320
wake_all_kswapds+0xac/0x1a0
__alloc_pages_slowpath.constprop.0+0x282/0xf80
__alloc_frozen_pages_noprof+0x32a/0x360
alloc_slab_page+0x2e/0x160
allocate_slab+0x82/0x420
new_slab+0x52/0xb0
refill_objects+0x13d/0x190
refill_sheaf+0x5d/0xd0
__pcs_replace_empty_main+0x230/0xb10
[...]
other info that might help us debug this:
Chain exists of:
&p->pi_lock --> kswapd_wakeup --> &pgdat->kswapd_wait
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&pgdat->kswapd_wait);
lock(kswapd_wakeup);
lock(&pgdat->kswapd_wait);
lock(&p->pi_lock);
*** DEADLOCK ***
3 locks held by git/6660:
#0: ffff8e519f0e9e20 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: lookup_slow+0x2d/0x60
#1: ffffffff8a31c460 (kswapd_wakeup){-.-.}-
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: validate TX status rate metadata
minstrel_ht_tx_status() converts the HT/VHT rate reported in a TX status
into a group and rate index and uses those to index the minstrel_ht rate
tables. The existing validation only checked that an entry was present
and had tries recorded; it did not check that the reported MCS, spatial
stream count and bandwidth are representable by the tables, so malformed
metadata passed to minstrel_ht_get_stats() or
minstrel_ht_ri_get_stats() could be used as an out-of-bounds index.
Validate the rate metadata in the common TX status path instead of only
in minstrel_ht, since the values are used by more than rate control.
The legacy ieee80211_tx_rate array and the rate_info based entries are
sanitized in ieee80211_tx_status_ext() and ieee80211_tx_rate_update()
before any consumer runs: an entry that does not describe a valid rate
for its encoding is dropped. minstrel_ht keeps the checks that depend
on its own tables, i.e. the supported number of spatial streams, the MCS
group size and the supported bandwidths.
This does not take away the driver's responsibility to report sane
values, it only prevents a single bad report from corrupting mac80211
state. No WARN_ON() is added: with panic_on_warn a driver bug would
otherwise turn into a denial of service. |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: ath9k: reject short WMI command responses
ath9k_wmi_rsp_callback() removes the validated WMI header and copies
the number of bytes expected by the waiting command into its response
buffer. A device response shorter than that expectation can therefore
be read beyond the skb payload.
Record -EMSGSIZE for a short response, complete the waiter, and return
the stored status from the command path. This also prevents callers from
consuming stale response bytes as a successful reply. |
| In the Linux kernel, the following vulnerability has been resolved:
blk-cgroup: save IRQ state in blkg_tryget_closest()
bio_set_dev() associates the bio with a blkg through bio_associate_blkg().
If the blkg lookup misses, blkg_tryget_closest() takes q->queue_lock with
spin_lock_irq() and releases it with spin_unlock_irq(), which
unconditionally enables local interrupts.
Callers may call bio_set_dev() with interrupts already disabled, e.g.
dm-thin's pool_map() does so while holding pool->lock taken with
spin_lock_irq(). The nested spin_unlock_irq() then enables interrupts
while pool->lock is still held, so an I/O completion softirq can run on
the same CPU, re-acquire pool->lock (thin_endio(), or overwrite_endio()
-> complete_mapping_preparation()) and deadlock. lockdep reports this
as inconsistent SOFTIRQ-ON-W to IN-SOFTIRQ-W usage.
Commit 3a762de55b4e ("block: save irq state in blkg_lookup_create()")
fixed the same problem while the lock lived in blkg_lookup_create(), but
commit 9327a865e395 ("blk-cgroup: don't nest queue_lock under rcu in
blkg_lookup_create()") moved the locking into blkg_tryget_closest() and
reverted it to spin_lock_irq().
Save and restore the caller's IRQ state instead. |
| In the Linux kernel, the following vulnerability has been resolved:
accel/amdxdna: Disable device buffer exporting
Device buffers are never intended to be exported. Disable exporting
support explicitly. |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: Hold map BTF for the memory allocator destructor record
bpf_ma_set_dtor() duplicates map->record so that the bpf_mem_alloc
destructor can release the special fields of hash and rhash map elements
once the allocator frees them for good. btf_record_dup() only acquires
references on kernel and module BTF. Fields whose types live in the map
BTF keep pointing into it: a kptr to a local type refers to map->btf,
and a list_head or rb_root field carries a value_rec owned by the struct
meta table of map->btf.
That borrowed state can outlive the map. When RCU callbacks are still in
flight, bpf_mem_alloc_destroy() copies the allocator and defers the final
drain, together with the destructor context, to a workqueue.
bpf_map_free() then frees map->record and drops the map's BTF reference
as soon as map_free() returns. Once the program that loaded the BTF is
gone as well, the BTF is freed while the worker still uses the
duplicate. The worker dereferences it through btf_is_kernel() and
btf_find_struct_meta() in bpf_obj_free_fields() when destroying elements
that were freed under RCU, and through btf_is_kernel() in
btf_record_free() when releasing the context itself:
BUG: KASAN: slab-use-after-free in btf_is_kernel+0x19/0x30
Read of size 1 at addr ffff88811505dce8 by task kworker/u16:2/50
Workqueue: events_unbound free_mem_alloc_deferred
Call Trace:
btf_is_kernel+0x19/0x30
btf_record_free+0xc7/0xf0
htab_dtor_ctx_free+0x1a/0x30
free_mem_alloc_no_barrier+0x39/0x230
free_mem_alloc_deferred+0x2a/0x40
process_scheduled_works+0x5ce/0x9d0
worker_thread+0x42a/0x5e0
kthread+0x1f5/0x230
ret_from_fork+0x1dd/0x390
ret_from_fork_asm+0x1a/0x30
Allocated by task 358:
__kmalloc_cache_noprof+0x287/0x510
btf_new_fd+0xf7/0x3d0
__sys_bpf+0x487/0x840
Freed by task 0:
kfree+0x186/0x560
rcu_core+0x6f6/0xd40
Freeing a map that still holds more elements than the allocator's high
watermark is enough to get there, because the bulk free during teardown
queues the RCU callback that makes bpf_mem_alloc_destroy() defer.
Non-preallocated hash maps and resizable hash maps both register the
destructor and are affected alike.
Keep one reference on the map BTF in the destructor context. Every
non-kernel pointer in the duplicated record is either map->btf or memory
owned by it, so a single reference covers kptrs, list heads, and rb
roots, and mirrors what bpf_map_meta_alloc() does for the duplicated
record of an inner map. Release it only after the duplicated record has
been freed: the worker is preemptible and not in an RCU read-side
critical section, so dropping the last reference first would let the
BTF be freed while btf_record_free() still reads its fields. |
| In the Linux kernel, the following vulnerability has been resolved:
net: sparx5: skip ptp deinit if init was skipped
sparx5_ptp_init() returns early on the base lan969x variants
because they do not have the SPX5_FEATURE_PTP flag. It also returns early
when no "ptp" interrupt is described. Unbinding the driver then causes a
NULL pointer dereference when cleaning up uninitialized tx_skbs queues:
Unable to handle kernel NULL pointer dereference at virtual address
0000000000000008
Call trace:
skb_queue_purge_reason+0x68/0x120 (P)
sparx5_ptp_deinit+0x64/0xc0
mchp_sparx5_remove+0x38/0x70
platform_remove+0x20/0x30
device_remove+0x4c/0x80
Before per-port tx_skbs were added, a NULL dereference would have happened
when calling ptp_clock_unregister() on the never-registered PTP clocks.
Fix by returning early in sparx5_ptp_deinit() if PTP is not used. |
| In the Linux kernel, the following vulnerability has been resolved:
ipv4: free inet_opt and ireq_opt after an RCU grace period
tcp_v4_syn_recv_sock() transfers ownership of ireq->ireq_opt to the
child socket (newinet->inet_opt) without copying it.
Another cpu can concurrently process a retransmitted SYN for the same
request socket, and send a SYNACK from tcp_check_req().
tcp_v4_send_synack() and inet_csk_route_req() read ireq->ireq_opt
under rcu_read_lock() only, and ip_build_and_send_pkt() and
ip_options_build() then read opt->optlen twice.
Note that the SYNACK timer itself is not an issue: it holds a
reference on its request socket, and inet_csk_reqsk_queue_drop()
calls timer_delete_sync() before the child can be freed.
Since commit 079096f103fa ("tcp/dccp: install syn_recv requests
into ehash table"), request sockets are processed without holding
the listener lock, so nothing prevents the child socket from being
freed while the SYNACK is still being built. TCP child sockets do
not have SOCK_RCU_FREE, and inet_sock_destruct() frees inet_opt
with a plain kfree(), leading to a use-after-free in
ip_options_build().
A similar issue exists with request socket migration
(net.ipv4.tcp_migrate_req=1, or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE
program). reqsk_timer_handler() clones the request socket with
inet_reqsk_clone(), so that the old request socket and its clone
share the same ireq_opt, then reqsk_migrate_reset() clears the
pointer in the old one. Another cpu holding a reference on the old
request socket can still be using these options (sending a SYNACK,
or creating a child in tcp_v4_syn_recv_sock()) when the clone is
freed, and tcp_v4_reqsk_destructor() also uses a plain kfree().
Readers already use RCU, and other paths replacing inet_opt
(do_ip_setsockopt(), cipso_v4_sock_setattr()...) already use
kfree_rcu(). Use kfree_rcu() in inet_sock_destruct() and
tcp_v4_reqsk_destructor() as well.
IPv6 is not affected by the first issue, because tcp_v6_syn_recv_sock()
duplicates the options. tcp_v6_reqsk_destructor() has the same
migration issue with ipv6_opt, which is only set by CALIPSO. This
will be addressed in a separate patch. |
| In the Linux kernel, the following vulnerability has been resolved:
sched/core: Avoid false migration warning for proxy donors
Proxy execution can move a blocked donor's scheduling context to the
lock owner's CPU even when the donor is migration-disabled. The donor
does not execute there, and its original execution CPU remains recorded
in wake_cpu.
set_task_cpu() warns unconditionally for migration-disabled tasks, so a
subsequent proxy migration or the wakeup path returning the donor home
triggers a false positive: moving a blocked scheduling context does not
violate the migration-disabled execution context.
For example, creating a mutex owner on CPU1 and a migration-disabled
waiter on CPU0 can trigger the following warning:
proxy_migrate_repro: donor blocking on CPU0 with migration disabled
proxy_migrate_repro: donor moved from CPU0 to CPU1
WARNING: kernel/sched/core.c:3389 at set_task_cpu+0x1d3/0x280
...
Call Trace:
try_to_wake_up+0x43f/0x780
__mutex_unlock_slowpath+0x330/0x540
owner_fn+0x9f/0xc0 [proxy_migrate_repro]
...
proxy_migrate_repro: donor woke on CPU0, task_cpu=0
proxy_migrate_repro: completed
Exclude blocked proxy donors from the warning. The proxy wakeup path
restores an executable placement before clearing the blocked state. |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: avoid WARN in set_bitrate_mask when sdata not in driver
ieee80211_set_bitrate_mask() checks if the interface is running via
ieee80211_sdata_running(), but it does not check if the interface is
still present in the driver.
When sdata is running but IEEE80211_SDATA_IN_DRIVER is not set, the
call reaches drv_set_bitrate_mask() in driver-ops.h which hits
wlan1: Failed check-sdata-in-driver check, flags: 0x0
WARNING: net/mac80211/driver-ops.h:884 at drv_set_bitrate_mask
Syzkaller triggers this via wext SIOCSIWRATE ioctl. The Call Trace shows
wext_ioctl_dispatch() in wext-core.c dispatching the ioctl, calling
ioctl_standard_call() for SIOCSIWRATE, which calls cfg80211_wext_siwrate()
in wext-compat.c. That builds a bitrate mask and calls
rdev_set_bitrate_mask() which ends up in ieee80211_set_bitrate_mask() in
cfg.c. The interface is marked running via SDATA_STATE_RUNNING but
flags is 0, so check_sdata_in_driver() fails.
When the interface is being torn down, or when wext ioctl is issued
during interface bringup before drv_add_interface() sets IN_DRIVER, the
running check passes while IN_DRIVER is clear.
Check IEEE80211_SDATA_IN_DRIVER in ieee80211_set_bitrate_mask() before
calling the driver, returning -ENETDOWN. This avoids the WARN_ONCE in
driver-ops.h and matches other cfg.c operations that bail early when not
in driver.
This change should be safe because wiphy mutex is held in
cfg80211_wext_siwrate() via guard(wiphy), and IN_DRIVER is set/cleared
under RTNL and wiphy paths in drv_add_interface() and
drv_remove_interface() in driver-ops.c, so the check is race-free
against driver add/remove. Returning -ENETDOWN is the same error other
not-running paths use and does not introduce new locking.
[also add second syzbot report] |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: rsi: fix heap OOB write on key removal
When a key is removed (data == NULL), rsi_hal_load_key() runs:
memset(&set_key[FRAME_DESC_SZ], 0, frame_len - FRAME_DESC_SZ);
set_key is a struct rsi_set_key *, so the subscript is scaled by
sizeof(struct rsi_set_key) (160 bytes): &set_key[FRAME_DESC_SZ] is
skb->data + 2560, and the memset writes 144 zero bytes starting
2.4KB past the end of the 160-byte skb data buffer, corrupting
unrelated heap objects. The intended byte offset would have been
(u8 *)set_key + FRAME_DESC_SZ.
The write fires on every DISABLE_KEY callback, so plain disconnects,
roams and interface teardowns trigger it on real networks.
The memset is redundant: the whole buffer is zeroed right after
allocation, so the frame sent to the device is byte-identical
without it. Drop the else branch; normal operation is unaffected.
Discovered by Atuin - Automated Vulnerability Discovery Engine. |
| In the Linux kernel, the following vulnerability has been resolved:
net: iptunnel: fix stale transport header during tunnel decapsulation
Syzbot reported a crash in qdisc_pkt_len_segs_init() caused by a stale
transport_header offset after tunnel decapsulation.
BUG: unable to handle page fault for address: ffffed102091a42e
Oops: Oops: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 340 Comm: qdisc_uaf_repro Not tainted 7.2.0-rc4-00061-g248951ddc14d #256 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__asan_load2
<IRQ>
qdisc_pkt_len_segs_init (net/core/dev.c:4145)
__dev_queue_xmit (net/core/dev.c:4787)
br_dev_queue_push_xmit (net/bridge/br_forward.c:53)
br_handle_frame_finish (net/bridge/br_input.c:229)
br_handle_frame (net/bridge/br_input.c:315)
__netif_receive_skb_core.constprop.0 (net/core/dev.c:6099)
__netif_receive_skb_list_core (net/core/dev.c:6287)
netif_receive_skb_list_internal (net/core/dev.c:6445)
napi_complete_done (net/core/dev.c:6813)
gro_cell_poll (net/core/gro_cells.c:74)
__napi_poll (net/core/dev.c:7735)
net_rx_action (net/core/dev.c:7798 net/core/dev.c:7955)
handle_softirqs (kernel/softirq.c:622)
do_softirq (kernel/softirq.c:523 kernel/softirq.c:510 )
__local_bh_enable_ip (kernel/softirq.c:450)
tun_get_user (drivers/net/tun.c:1986 (discriminator 1))
tun_chr_write_iter (drivers/net/tun.c:2032)
The issue is completely latent until qdisc read transport header in
commit 7fb4c1967011 ("net: pull headers in qdisc_pkt_len_segs_init()").
The crash requires four conditions to line up:
1. The incoming packet is encapsulated and carries GSO metadata. The outer
transport header offset is stored in skb->transport_header while the
packet is still in the outer tunnel context.
2. The tunnel receiver strips the outer headers. skb->data is advanced to
the inner frame, but skb->transport_header is left pointing to the
now-removed outer L4 header, so it becomes a negative offset relative to
the new data.
3. The inner frame is not delivered to the local IP stack. Instead, it
is forwarded at L2 by a bridge or HSR, so ip_rcv_core() never runs and
the transport header is not reset to the inner L4 offset.
4. The forwarding path calls __dev_queue_xmit(), which enters
qdisc_pkt_len_segs_init(). That function computes the GSO header length
from skb_transport_offset(skb). Because the offset is negative, the
unsigned cast overflows and pskb_may_pull(skb, hdr_len +
sizeof(struct tcphdr)) reads past the end of the skb, triggering a
KASAN fault or page fault.
The issue specifically requires GSO packets (shinfo->gso_size != 0), which
are processed/aggregated through gro_cells. Fix this by clearing
transport_header to the ~0U sentinel in gro_cell for all tunnnel driver.
GTP does not support GRO/GSO, drop the evil GSO packets in GTP directly. |
| In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix missing iov bounds check in parse_posix_sids()
In parse_posix_sids(), sidsbuf_end is calculated using the server-supplied
out_len without being validated against the actual length of the received
iov (iov_len).
If a server provides an inflated out_len, sidsbuf_end will point past the
end of the iov. This defeats the bounds guards in posix_info_sid_size(),
allowing out-of-bounds reads into adjacent kernel memory.
Fix this by rejecting responses where the calculated sidsbuf_end would
exceed the received iov boundaries or cause pointer wraparound. |
| In the Linux kernel, the following vulnerability has been resolved:
watchdog: rtd119x: Avoid division by zero
clk_get_rate() could return 0. Avoid a division by zero panic. |
| In the Linux kernel, the following vulnerability has been resolved:
net: xfrm: reject unrepresentable espintcp transport headers
ESP-in-TCP can hand xfrm packets whose transport header offset no longer
fits after the stream parser trims the TCP envelope. The plain transport
header reset truncates that offset and triggers the skb warning path.
Use the careful transport-header helper and drop the skb through the
existing XFRM error path when the offset cannot be represented. |
| In the Linux kernel, the following vulnerability has been resolved:
platform/x86: x86-android-tablets: hold device reference for secondary fwnode teardown
In gpio_secondary_fwnode_init(), acpi_bus_find_device_by_name() returns a
device reference, but the local dev variable is declared with
__free(put_device), dropping the reference at the end of each iteration.
Meanwhile, devm_add_action_or_reset() saves the dev pointer for
gpio_secondary_unset() without incrementing its reference count, which
could lead to a use-after-free during driver teardown if the device is
released in the interim.
Acquire an explicit device reference with get_device() when registering
the devres action, and drop it with put_device() inside
gpio_secondary_unset(). |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown
After a DESTROY_SESSION the per-session teardown path can free a
session while rpciod still holds an inflight callback rpc_task that
dereferences clp->cl_cb_session. nfsd4_probe_callback_sync() flushes
cl_callback_wq, but once nfsd4_run_cb_work() has called
rpc_call_async() the rpc_task lives on rpciod; flushing the workqueue
does not wait for it. rpc_shutdown_client() does drain rpciod tasks,
but uses a 1-second wait_event_timeout — tasks stuck in rpc_delay()
(e.g. 2-second NFS4ERR_DELAY retries) can outlive the drain.
destroy path rpciod
------------ ------
unhash_session(ses)
nfsd4_probe_callback_sync(clp)
flush_workqueue(cl_callback_wq)
/* returns; rpc_task still live */
nfsd4_put_session_locked(ses)
free_session(ses) -> kfree(ses)
nfsd4_cb_sequence_done()
reads cb_clp->cl_cb_session
/* freed slab */
A second window exists in nfsd4_process_cb_update(). When
__nfsd4_find_backchannel() returns NULL because unhash_session() has
already removed the destroyed session from cl_sessions,
setup_callback_client() takes the v4.1 early return so
clp->cl_cb_session = ses never fires and the field retains a pointer
to the about-to-be-freed session.
Fix both by converting cl_cb_session to an RCU-protected pointer:
- Move the cl_cb_session = ses assignment in setup_callback_client()
to after rpc_create() succeeds, so it is only published when a
working backchannel exists. Clear cl_cb_session on the error
return in nfsd4_process_cb_update(). Both stores use
rcu_assign_pointer().
- Annotate cl_cb_session with __rcu. All rpciod-side readers use
rcu_read_lock()/rcu_dereference() and check for NULL, bailing to
the appropriate error or requeue path:
encode_cb_sequence4args(), decode_cb_sequence4resok(),
nfsd41_cb_get_slot(), nfsd41_cb_release_slot(),
nfsd4_cb_prepare(), and nfsd4_cb_sequence_done().
- Switch __free_session() from kfree() to kfree_rcu() so the
session slab is not reclaimed until after an RCU grace period,
guaranteeing that rpciod readers inside rcu_read_lock() never
dereference freed memory.
- Pass the session pointer to the nfsd_cb_seq_status and
nfsd_cb_free_slot tracepoints instead of having them re-read
cl_cb_session.
- nfsd4_cb_prepare() calls rpc_exit() when the session is NULL,
routing through the done/release path to requeue the callback. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: release path refs on follow_down() error
nfsd_cross_mnt() initializes a local struct path with mntget() and
dget() before calling follow_down(). On a negative return the error
arm jumps to out without releasing those references:
err = follow_down(&path, follow_flags);
if (err < 0)
goto out;
follow_down() never drops the caller's entry-time refs on any error
sub-case; for example a pre-cross d_manage() failure leaves path
untouched, so the mntget()/dget() taken on entry survive the call.
Every other early-exit arm in nfsd_cross_mnt() (other-namespace
return, IS_ERR(exp2), and the success tail after the swap) already
calls path_put(&path); the err < 0 arm is the lone omission. The
leak inflates mnt_count and d_count on each failed cross-mount,
blocking umount and pinning dentries against the shrinker, and is
reachable by any authenticated NFS client through nfsd_lookup_dentry
or the NFSv4 READDIR encode path.
Fix by calling path_put(&path) before the goto out in the err < 0
arm so the entry-time refs are released on all follow_down() error
returns. |
