Vulnerabilidades do Linux Linux

In the Linux kernel, the following vulnerability has been resolved: rhashtable: clear stale iter->p on table restart rhashtable_walk_start_check() has two restart paths when resuming a walk. When iter->walker.tbl is valid, it re-validates iter->p against the table and sets iter->p = NULL if the object is gone. When iter->walker.tbl is NULL (table was freed during resize), it resets slot and skip but forgets to clear iter->p. rhashtable_walk_next() then dereferences the stale iter->p, reading freed memory. This is a use-after-free. Any caller that does multi-fragment rhashtable walks across walk_stop/walk_start boundaries is affected. Concrete cases include netlink_diag (__netlink_diag_dump in net/netlink/diag.c) and TIPC (tipc_nl_sk_walk in net/tipc/socket.c). Crash stack (netlink_diag): BUG: KASAN: slab-use-after-free in rhashtable_walk_next+0x365/0x3c0 Read of size 8 at addr ffff88801a9d2438 (freed kmalloc-2k, offset 1080) Call Trace: rhashtable_walk_next+0x365/0x3c0 (lib/rhashtable.c:1016) __netlink_diag_dump+0x160/0x760 (net/netlink/diag.c:122) netlink_diag_dump+0xc2/0x240 netlink_dump+0x5bc/0x1270 netlink_recvmsg+0x7a3/0x980 sock_recvmsg+0x1bc/0x200 __sys_recvfrom+0x1d4/0x2c0

In the Linux kernel, the following vulnerability has been resolved: KVM: nVMX: Hide shadow VMCS right after VMCLEAR free_nested() frees the shadow VMCS while vmcs01 still points to it. But because it is asynchronous with respect to loaded_vmcs_clear(), the vCPU might migrate before the pointer is cleared and __loaded_vmcs_clear() may then execute VMCLEAR. The VMCS needs to stay attached until its explicit VMCLEAR completes, but then it can be hidden and the page safely freed.

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages. Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages. Note #2, inheriting role.invalid when creating child shadow pages is also far from ideal; that flaw will be addressed separately.

In the Linux kernel, the following vulnerability has been resolved: s390/pkey: Check length in PKEY_VERIFYPROTK ioctl Explicitly check the buffer length request structure provided by user-space and fail, if it exceeds the buffer size.

In the Linux kernel, the following vulnerability has been resolved: s390/pkey: Check length in pkey_pckmo handler implementation Explicitly check the length of the target buffer in the pkey_pckmo implementation of the key_to_protkey() handler function. The handler function fails, if the generated output data exceeds the length of the provided target buffer.

In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent UAF caused by non-leader exec() race Wongi and Jungwoo decoded and reported a non-leader exec() related race which can result in an UAF: sys_timer_delete() exec() posix_cpu_timer_del() // Observes old leader p = pid_task(pid, pid_type); de_thread() switch_leader(); release_task(old_leader) __exit_signal(old_leader) sighand = lock(old_leader, sighand); posix_cpu_timers*_exit(); sighand = lock_task_sighand(p) unhash_task(old_leader); sh = lock(p, sighand) old_leader->sighand = NULL; unlock(sighand); (p->sighand == NULL) unlock(sh) return NULL; // Returns without action if(!sighand) return 0; free_posix_timer(); This is "harmless" unless the deleted timer was armed and enqueued in p->signal because on exec() a TGID targeted timer is inherited. As sys_timer_delete() freed the underlying posix timer object run_posix_cpu_timers() or any timerqueue related add/delete operations on other timers will access the freed object's timerqueue node, which results in an UAF. There is a similar problem vs. posix_cpu_timer_set(). For regular posix timers it just transiently returns -ESRCH to user space, but for the use case in do_cpu_nanosleep() it's the same UAF just that the k_itimer is allocated on the stack. Also posix_cpu_timer_rearm() fails to rearm the timer, which means it stops to expire. While debating solutions Frederic pointed out another problem: posix_cpu_timer_del(tmr) __exit_signal(p) posix_cpu_timers*_exit(p); unhash_task(p); p->sighand = NULL; sh = lock_task_sighand(p) sighand = p->sighand; if (!sighand) return NULL; lock(sighand); if (!sh) WARN_ON_ONCE(timer_queued(tmr)); On weakly ordered architectures it is not guaranteed that posix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit() when p->sighand is observed as NULL, which means the WARN() can be a false positive. Solve these issues by: 1) Changing the store in __exit_signal() to smp_store_release(). 2) Adding a smp_acquire__after_ctrl_dep() into the !sighand path of lock_task_sighand(). 3) Creating a helper function for looking up the task and locking sighand which does not return when sighand == NULL. Instead it retries the task lookup and only if that fails it gives up. 4) Using that helper in the three affected functions. #1/#2 ensures that the reader side which observes sighand == NULL also observes all preceeding stores, i.e. the stores in posix_cpu_timers*_exit() and the ones in unhash_task(). #3 ensures that the above described non-leader exec() situation is handled gracefully. When the task lookup returns the old leader, but sighand == NULL then it retries. In the non-leader exec() case the subsequent task lookup will observe the new leader due to #1/#2. In normal exit() scenarios the subsequent lookup fails. When the task lookup fails, the function also checks whether the timer is still enqueued and issues a warning if that's the case. Unfortunately there is nothing which can be done about it, but as the task is already not longer visible the timer should not be accessed anymore. This check also requires memory ordering, which is not provided when the first lookup fails. To achieve that the check is preceeded by a smp_rmb() which pairs with the smp_wmb() in write_seqlock() in __exit_signal(). That ensures that the stores in posix_cpu_timers*_exit() are visible. The history of the non-leader exec() issue goes back to the early days of posix CPU timers, which stored a pointer to the group leader task in the timer. That obviously fails when a non-leader exec() switches the leader. commit e0a70217107e ("posix-cpu-timers: workaround to suppress the problems with mt exec") added a temporary workaround for that in 2010 which surv ---truncated---

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_new_connection_cb() l2cap_sock_new_connection_cb() returned l2cap_pi(sk)->chan after release_sock(parent). Once the parent lock is dropped the newly enqueued child socket sk is reachable via the accept queue, so another task can accept and free it before the callback dereferences sk, resulting in a use-after-free. Rework the ->new_connection() op so the core, rather than the callback, owns the child channel's lifetime. The op now receives a pre-allocated new_chan and returns an errno instead of allocating and returning a channel. l2cap_new_connection() allocates the child channel and links it into the conn list via __l2cap_chan_add() before invoking the callback, so the conn-list reference keeps the channel alive once release_sock(parent) exposes the socket to other tasks. Channel configuration that was duplicated in l2cap_sock_init() and the various new_connection callbacks is consolidated into l2cap_chan_set_defaults(), which now inherits from the parent channel when one is supplied.

In the Linux kernel, the following vulnerability has been resolved: perf/core: Detach event groups during remove_on_exec perf_event_remove_on_exec() removes events by calling perf_event_exit_event(). For top-level events, this removes the event from the context with DETACH_EXIT only. This can leave inconsistent group state when a removed event is a group leader and the group contains siblings without remove_on_exec. If the group was active, the surviving siblings can remain active and attached to the removed leader's sibling list, but are no longer represented by a valid group leader on the PMU context active lists. A later close of the removed leader uses DETACH_GROUP and can promote the still-active siblings from this stale group state. The next schedule-in can then add an already-linked active_list entry again, corrupting the PMU context active list. With DEBUG_LIST enabled, this is caught as a list_add double-add in merge_sched_in(). Fix this by detaching group relationships when remove_on_exec removes an event. This preserves the existing task-exit and revoke behavior, while ensuring surviving siblings are ungrouped before the removed event leaves the context.

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: nv: Fix SPSR_EL2 restore in kvm_hyp_handle_mops() kvm_hyp_handle_mops() resets the single-step state machine as part of rewinding state for a MOPS exception by modifying vcpu_cpsr() and writing the result directly into hardware. In the case of nested virtualization, vcpu_cpsr() is a synthetic value such that the rest of KVM can deal with vEL2 cleanly. That means the value requires translation before being written into hardware, which is unfortunately missing from the MOPS handler. Fix it by directly modifying SPSR_EL2 and avoiding the synthetic state altogether, which will be resynchronized on the next 'full' exit back to KVM.

In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment() br_ip6_fragment() gets prevhdr, a pointer into the skb head, from ip6_find_1stfragopt(), then calls skb_checksum_help(). For a cloned skb skb_checksum_help() reallocates the head via pskb_expand_head(), leaving prevhdr dangling. It is later dereferenced in ip6_frag_next(), causing a use-after-free write. Save prevhdr's offset before skb_checksum_help() and recompute it after, like commit ef0efcd3bd3f ("ipv6: Fix dangling pointer when ipv6 fragment"). BUG: KASAN: slab-use-after-free in ip6_frag_next (net/ipv6/ip6_output.c:857) Write of size 1 at addr ffff888013ff5016 by task exploit/141 Call Trace: ... kasan_report (mm/kasan/report.c:595) ip6_frag_next (net/ipv6/ip6_output.c:857) br_ip6_fragment (net/ipv6/netfilter.c:212) nf_ct_bridge_post (net/bridge/netfilter/nf_conntrack_bridge.c:407) nf_hook_slow (net/netfilter/core.c:619) br_forward_finish (net/bridge/br_forward.c:66) __br_forward (net/bridge/br_forward.c:115) maybe_deliver (net/bridge/br_forward.c:191) br_flood (net/bridge/br_forward.c:245) br_handle_frame_finish (net/bridge/br_input.c:229) br_handle_frame (net/bridge/br_input.c:442) ... packet_sendmsg (net/packet/af_packet.c:3114) ... do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Kernel panic - not syncing: Fatal exception in interrupt

In the Linux kernel, the following vulnerability has been resolved: virtio-net: fix len check in receive_big() receive_big() bounds the device-announced length by (big_packets_num_skbfrags + 1) * PAGE_SIZE. That is still too loose: add_recvbuf_big() sets sg[1] to start at offset sizeof(struct padded_vnet_hdr) into the first page, so the chain actually carries hdr_len + (PAGE_SIZE - sizeof(padded_vnet_hdr)) + big_packets_num_skbfrags * PAGE_SIZE bytes -- 20 bytes less than the check allows for the common hdr_len == 12 case. A malicious virtio backend can announce a len in that gap. page_to_skb() then walks one frag past the page chain, storing a NULL page->private into skb_shinfo()->frags[MAX_SKB_FRAGS], which is both an out-of-bounds write past the static frag array and a NULL frag handed up the rx path. Bound len by the size add_recvbuf_big() actually advertised.

In the Linux kernel, the following vulnerability has been resolved: net: qualcomm: rmnet: validate MAP frame length before ingress parsing When ingress deaggregation is disabled, rmnet_map_ingress_handler() passes the skb straight to __rmnet_map_ingress_handler(), skipping the length validation that rmnet_map_deaggregate() performs on the aggregated path. The parser then dereferences the MAP header and csum header/trailer based on the on-wire pkt_len without checking skb->len, so a short frame is read out of bounds: BUG: KASAN: slab-out-of-bounds in rmnet_map_checksum_downlink_packet Read of size 1 at addr ffff88801118ed00 by task exploit/147 Call Trace: ... rmnet_map_checksum_downlink_packet (drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c:413) __rmnet_map_ingress_handler (drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c:96) rmnet_rx_handler (drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c:129) __netif_receive_skb_core.constprop.0 (net/core/dev.c:6089) netif_receive_skb (net/core/dev.c:6460) tun_get_user (drivers/net/tun.c:1955) tun_chr_write_iter (drivers/net/tun.c:2001) vfs_write (fs/read_write.c:688) ksys_write (fs/read_write.c:740) do_syscall_64 (arch/x86/entry/syscall_64.c:94) ... Factor that validation out of rmnet_map_deaggregate() into rmnet_map_validate_packet_len() and run it on the no-aggregation path too. The MAP header is bounds-checked first, since this path can receive a frame shorter than the header.

In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() When the scatterlist ring is full or nearly full, bpf_msg_push_data() enters a copy fallback path and computes copy + len for the page allocation size. Since len comes from BPF with arg3_type = ARG_ANYTHING and both are u32, a crafted len can wrap the sum to a small value, causing an undersized allocation followed by an out-of-bounds memcpy. BUG: unable to handle page fault for address: ffffed104089a402 Oops: Oops: 0000 [#1] SMP KASAN NOPTI Call Trace: __asan_memcpy (mm/kasan/shadow.c:105) bpf_msg_push_data (net/core/filter.c:2852 net/core/filter.c:2788) bpf_prog_9ed8b5711920a7d7+0x2e/0x36 sk_psock_msg_verdict (net/core/skmsg.c:934) tcp_bpf_sendmsg (net/ipv4/tcp_bpf.c:421 net/ipv4/tcp_bpf.c:584) __sys_sendto (net/socket.c:2206) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Add an overflow check before the allocation.

In the Linux kernel, the following vulnerability has been resolved: net: usb: net1080: validate packet_len before pad-byte access in rx_fixup For an even packet_len, net1080_rx_fixup() reads the pad byte at skb->data[packet_len] before the skb->len != packet_len check further down, and packet_len is only bounded against NC_MAX_PACKET. A malicious NetChip 1080 device can send a short frame advertising a large even packet_len (e.g. 0x4000), so the pad-byte read lands past the end of the skb: BUG: KASAN: slab-out-of-bounds in net1080_rx_fixup Read of size 1 at addr ffff8880106c83c6 by task ksoftirqd/0/14 ... net1080_rx_fixup (drivers/net/usb/net1080.c:384) usbnet_bh (drivers/net/usb/usbnet.c:1589) process_one_work (kernel/workqueue.c:3322) bh_worker (kernel/workqueue.c:3708) tasklet_action (kernel/softirq.c:965) handle_softirqs (kernel/softirq.c:622) ... Reject the frame when packet_len >= skb->len before reading.

In the Linux kernel, the following vulnerability has been resolved: drm/edid: fix OOB read in drm_parse_tiled_block() drm_parse_tiled_block() casts the DisplayID block to a struct displayid_tiled_block and reads the full fixed layout up to tile->topology_id[7] without checking block->num_bytes. The DisplayID iterator only validates the declared payload length, so a crafted EDID can advertise a tiled-display block (tag DATA_BLOCK_TILED_DISPLAY, or DATA_BLOCK_2_TILED_DISPLAY_TOPOLOGY for v2.0) with a small num_bytes at the end of a DisplayID extension. The read then runs past the end of the exact-sized kmemdup()'d EDID allocation, a heap out-of-bounds read. Reject blocks shorter than the spec's 22-byte tiled payload before reading the fixed struct, as drm_parse_vesa_mso_data() already does. BUG: KASAN: slab-out-of-bounds in drm_edid_connector_update Read of size 2 at addr ffff888010077700 by task exploit/147 dump_stack_lvl (lib/dump_stack.c:94 ...) print_report (mm/kasan/report.c:378 ...) kasan_report (mm/kasan/report.c:595) drm_edid_connector_update (drivers/gpu/drm/drm_edid.c:7581) bochs_connector_helper_get_modes (drivers/gpu/drm/tiny/bochs.c:574) drm_helper_probe_single_connector_modes (drivers/gpu/drm/drm_probe_helper.c:426) status_store (drivers/gpu/drm/drm_sysfs.c:219) ... vfs_write (fs/read_write.c:595 fs/read_write.c:688) ksys_write (fs/read_write.c:740)

In the Linux kernel, the following vulnerability has been resolved: net, bpf: check master for NULL in xdp_master_redirect() xdp_master_redirect() dereferences the result of netdev_master_upper_dev_get_rcu() without a NULL check, but that helper returns NULL when the receiving device has no upper-master adjacency. The reach guard only checks netif_is_bond_slave(). On bond slave release bond_upper_dev_unlink() drops the upper-master adjacency before clearing IFF_SLAVE, so an XDP_TX reaching xdp_master_redirect() in that window still passes netif_is_bond_slave() while master is already NULL, and faults on master->flags at offset 0xb0: BUG: kernel NULL pointer dereference, address: 00000000000000b0 RIP: 0010:xdp_master_redirect (net/core/filter.c:4432) Call Trace: xdp_master_redirect (net/core/filter.c:4432) bpf_prog_run_generic_xdp (include/net/xdp.h:700) do_xdp_generic (net/core/dev.c:5608) __netif_receive_skb_one_core (net/core/dev.c:6204) process_backlog (net/core/dev.c:6319) __napi_poll (net/core/dev.c:7729) net_rx_action (net/core/dev.c:7792) handle_softirqs (kernel/softirq.c:622) __dev_queue_xmit (include/linux/bottom_half.h:33) packet_sendmsg (net/packet/af_packet.c:3082) __sys_sendto (net/socket.c:2252) Kernel panic - not syncing: Fatal exception in interrupt The missing check dates back to the original code; commit 1921f91298d1 ("net, bpf: fix null-ptr-deref in xdp_master_redirect() for down master") later added the master->flags read where the fault now lands but kept the unconditional deref. Check master for NULL before use; a NULL master is treated the same as one that is not up.

In the Linux kernel, the following vulnerability has been resolved: tipc: fix use-after-free of the discoverer in tipc_disc_rcv() bearer_disable() frees b->disc with tipc_disc_delete()'s plain kfree(), but tipc_disc_rcv() still dereferences b->disc in RX softirq under rcu_read_lock() (tipc_udp_recv -> tipc_rcv -> tipc_disc_rcv). L2 bearers are safe thanks to the synchronize_net() in tipc_disable_l2_media(), but the UDP bearer defers that call to the cleanup_bearer() workqueue, so the discoverer is freed with no grace period: BUG: KASAN: slab-use-after-free in tipc_disc_rcv (net/tipc/discover.c:149) Read of size 8 at addr ffff88802348b728 by task poc_tipc/184 <IRQ> tipc_disc_rcv (net/tipc/discover.c:149) tipc_rcv (net/tipc/node.c:2126) tipc_udp_recv (net/tipc/udp_media.c:391) udp_rcv (net/ipv4/udp.c:2643) ip_local_deliver_finish (net/ipv4/ip_input.c:241) </IRQ> Freed by task 181: kfree (mm/slub.c:6565) bearer_disable (net/tipc/bearer.c:418) tipc_nl_bearer_disable (net/tipc/bearer.c:1001) The bearer is freed with kfree_rcu(); free the discoverer the same way. Add an rcu_head to struct tipc_discoverer and free it and its skb from an RCU callback. Because the RCU callback (tipc_disc_free_rcu) lives in module text, a call_rcu() that is still pending when the tipc module is unloaded would invoke a freed function. Add an rcu_barrier() to tipc_exit() after the bearer subsystem has been torn down, so all pending discoverer callbacks have run before the module text goes away. Reachable from an unprivileged user namespace: the TIPCv2 genl family is netnsok and its bearer commands have no GENL_ADMIN_PERM. Needs CONFIG_TIPC and CONFIG_TIPC_MEDIA_UDP.