Search Results (6374 CVEs found)

CVE Vendors Products Updated CVSS v3.1
CVE-2026-72344 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: TC, skip peer flow cleanup when LAG seq is unavailable mlx5_lag_get_dev_seq() will return error when the peer isn't in the LAG or when no device is marked as master. Result bad memory access and kernel crash[1]. Hence, skip the peer when lookup fails. Note: In case there are peer flows, they are cleaned before LAG cleared the master mark. [1] RIP: 0010:mlx5e_tc_del_fdb_peers_flow+0x3d/0x350 [mlx5_core] Call Trace: <TASK> mlx5e_tc_clean_fdb_peer_flows+0xc1/0x130 [mlx5_core] mlx5_esw_offloads_unpair+0x3a/0x400 [mlx5_core] mlx5_esw_offloads_devcom_event+0xee/0x360 [mlx5_core] mlx5_devcom_send_event+0x7a/0x140 [mlx5_core] mlx5_esw_offloads_devcom_cleanup+0x2f/0x90 [mlx5_core] mlx5e_tc_esw_cleanup+0x28/0xf0 [mlx5_core] mlx5e_rep_tc_cleanup+0x19/0x30 [mlx5_core] mlx5e_cleanup_uplink_rep_tx+0x36/0x40 [mlx5_core] mlx5e_cleanup_rep_tx+0x55/0x60 [mlx5_core] mlx5e_detach_netdev+0x96/0xf0 [mlx5_core] mlx5e_netdev_change_profile+0x5b/0x120 [mlx5_core] mlx5e_netdev_attach_nic_profile+0x1b/0x30 [mlx5_core] mlx5e_vport_rep_unload+0xdd/0x110 [mlx5_core] __esw_offloads_unload_rep+0x81/0xb0 [mlx5_core] mlx5_eswitch_unregister_vport_reps+0x1d7/0x220 [mlx5_core] mlx5e_rep_remove+0x22/0x30 [mlx5_core] device_release_driver_internal+0x194/0x1f0 bus_remove_device+0xe8/0x1b0 device_del+0x159/0x3c0 mlx5_rescan_drivers_locked+0xbc/0x2d0 [mlx5_core] mlx5_unregister_device+0x54/0x80 [mlx5_core] mlx5_uninit_one+0x73/0x130 [mlx5_core] remove_one+0x78/0xe0 [mlx5_core] pci_device_remove+0x39/0xa0
CVE-2026-72385 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: tracing/fprobe: Fix NULL pointer dereference in fprobe_fgraph_entry() fprobe_fgraph_entry() sizes a shadow-stack reservation in one walk of the per-ip fprobe list and fills it in a second walk, both under rcu_read_lock() only. A fprobe registered on an already-live ip can become visible between the two walks, so the fill walk processes an exit_handler the sizing walk did not count and used runs past reserved_words. If the sizing walk counted nothing, fgraph_data is NULL and the first write_fprobe_header() faults: Oops: general protection fault, probably for non-canonical address ... KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:fprobe_fgraph_entry+0xa38/0xf10 kernel/trace/fprobe.c:167 Call Trace: <TASK> function_graph_enter_regs+0x44c/0xa10 kernel/trace/fgraph.c:677 ftrace_graph_func+0xc5/0x140 arch/x86/kernel/ftrace.c:671 __kernel_text_address+0x9/0x40 kernel/extable.c:78 arch_stack_walk+0x117/0x170 arch/x86/kernel/stacktrace.c:26 kmem_cache_free+0x188/0x580 mm/slub.c:6378 tcp_data_queue+0x18d/0x6550 net/ipv4/tcp_input.c:5590 [...] </TASK> The list cannot be frozen across the two walks, so skip a node that does not fit the reservation and count it as missed.
CVE-2026-74274 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: cxl/region: Fill first free targets[] slot during auto-discovery Any invalid endpoint decoder pointer in the target array of an active region is not allowed by cxl driver. This means cxl driver always assumes the first p->nr_targets entries of the target array in an auto-assembly region are valid. However, there are scenarios that could leave NULL endpoint decoder pointer holes in the target array. 1. When cxl_cancel_auto_attach() removes an endpoint decoder from a target array, the target slot is set to NULL. If the removed endpoint decoder is not the last element in the target array, the target array will contain a NULL hole. 2. When a auto-assembly region removes an assigned endpoint decoder, if the removed endpoint decoder is not the last element in the target array, always remains a NULL hole in the target array. When a NULL pointer hole exists in a region's target array, it introduces two potential problems: 1. Access an endpoint decoder via a NULL pointer. it always trigger calltrace like that. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000008: 0000 [#1] SMP KASAN PTI RIP: 0010:cxl_calc_interleave_pos+0x26/0x810 [cxl_core] Call Trace: <TASK> cxl_region_attach+0xc50/0x2140 [cxl_core] cxl_add_to_region+0x321/0x2330 [cxl_core] discover_region+0x92/0x150 [cxl_port] device_for_each_child+0xf3/0x170 cxl_port_probe+0x150/0x200 [cxl_port] cxl_bus_probe+0x4f/0xa0 [cxl_core] really_probe+0x1c8/0x960 __driver_probe_device+0x323/0x450 driver_probe_device+0x45/0x120 __device_attach_driver+0x15d/0x280 bus_for_each_drv+0x10f/0x190 2. Not having enough valid endpoint decoders attached to an auto-assembly region. if an auto-assembly region is created with lock flag or assigned endpoint decoder with lock flag, which means assigned endpoint decoder will not be reset during detaching, they could re-attach to the auto-assembly region again. But cxl region driver relies on p->nr_targets to verify whether the required number of endpoint decoders has been attached, and NULL endpoint decoder pointers are still counted in that case. To fix above issues, adjust cxl_region_attach_auto() logic to find the first free target slot for endpoint decoder attachment, this ensures NULL holes in the target array are filled, rather than adding new endpoint decoders at the tail of the target array.
CVE-2026-72432 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: tpm_crb: Check ACPI_COMPANION() against NULL during probe Every platform driver can be forced to match a device that doesn't match its list of device IDs because of device_match_driver_override(), so platform drivers that rely on the existence of a device's ACPI companion object need to verify its presence. Accordingly, add a requisite ACPI_COMPANION() check against NULL to the tpm_crb driver.
CVE-2026-74286 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: net: pfcp: allocate per-cpu tstats for PFCP netdevs PFCP uses dev_get_tstats64() as its ndo_get_stats64 callback, but pfcp_link_setup() does not request NETDEV_PCPU_STAT_TSTATS. The net core therefore leaves dev->tstats NULL for PFCP devices. Creating a PFCP rtnetlink device can immediately ask the new netdev for stats while building the RTM_NEWLINK notification. That reaches dev_get_tstats64() and dereferences the NULL dev->tstats pointer. Set pcpu_stat_type to NETDEV_PCPU_STAT_TSTATS during PFCP link setup so the net core allocates the storage expected by dev_get_tstats64().
CVE-2026-74303 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_qca: fix NULL pointer dereference in qca_dmp_hdr() for non-serdev device hu->serdev is NULL for hci_uart attached via non-serdev paths, but qca_dmp_hdr() unconditionally dereferences hu->serdev->dev.driver->name, causing a NULL pointer dereference. Fix by guarding the dereference with a NULL check and falling back to "hci_ldisc_qca" for the non-serdev case.
CVE-2026-74322 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: wifi: mt76: mt7996: Fix possible NULL pointer dereference in mt7996_mac_write_txwi_80211() For injected frames (e.g. via radiotap), mac80211 can pass info->control.vif = NULL, as explicitly noted in struct ieee80211_tx_info. Check vif pointer before executing ieee80211_vif_is_mld() in mt7996_mac_write_txwi_80211 routine in order to avoid a possible NULL pointer dereference.
CVE-2026-74414 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: hfsplus: Remove the duplicate attr inode dirty marking action Syzbot reported a null-ptr-deref in [1]. If the attributes file is not loaded during system mount, a trigger occurs [1] when setxattr is executed in userspace. Remove the first mark attr inode dirty operation. [1] KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] Call Trace: hfsplus_setxattr+0x124/0x340 fs/hfsplus/xattr.c:555 hfsplus_trusted_setxattr+0x40/0x60 fs/hfsplus/xattr_trusted.c:30 __vfs_setxattr+0x43c/0x480 fs/xattr.c:218 __vfs_setxattr_noperm+0x12d/0x660 fs/xattr.c:252 vfs_setxattr+0x163/0x360 fs/xattr.c:339 do_setxattr fs/xattr.c:654 [inline]
CVE-2026-74304 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_qca: fix NULL pointer dereference in qca_setup() for non-serdev device hu->serdev is NULL for hci_uart attached via non-serdev paths, but qca_setup() unconditionally calls serdev_device_get_drvdata(hu->serdev) and dereferences the result, causing a NULL pointer dereference. Fix by guarding the dereference with a NULL check, consistent with the rest of qca_setup().
CVE-2026-74395 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: RDMA/mlx5: Fix devx subscribe-event unwind NULL dereference MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT() links event_sub into sub_list before initializing the fields used by the shared error path. If eventfd_ctx_fdget() then fails, the unwind path dereferences event_sub->ev_file in uverbs_uobject_put() and calls subscribe_event_xa_dealloc() with an unset xa_key_level1. subscribe_event_xa_alloc() creates the XA entry exactly once for a given key_level1, on the first occurrence of that key. The unwind path must therefore call subscribe_event_xa_dealloc() exactly once for it as well. Enforce that by adding devx_key_in_sub_list() and calling subscribe_event_xa_dealloc() only when the last matching pending entry is being cleaned up.
CVE-2026-72502 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF) When MTU is large, ip6_default_advmss() can return IPV6_MAXPLEN (65535). This is interpreted by TCP as mss_clamp, allowing the MSS to reach 65535. However, 0xFFFF is also used as a magic value GSO_BY_FRAGS in the kernel. If a TCP packet with gso_size=0xFFFF is passed to skb_segment(), it will be mistakenly treated as GSO_BY_FRAGS, leading to a NULL pointer dereference because local TCP packets do not use frag_list. Fix this by returning min(IPV6_MAXPLEN, GSO_BY_FRAGS - 1) (65534) from ip6_default_advmss() when MTU is large. Also update the stale comment in ip6_default_advmss() which suggested that IPV6_MAXPLEN is returned to mean "any MSS".
CVE-2026-74266 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_dualpi2: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen Whenever dualpi2 drops packets during peek, it calls qdisc_tree_reduce_backlog. An issue arises because it calls qdisc_tree_reduce_backlog before it reincrements the qlen. If qlen drops to zero, but peek returns an skb, the parent's qlen_notify callback will be executed even though dualpi2 still has 1 packet on the queue and, thus, mistakenly deactivates the parent's class which leads to a null-ptr-deref: [ 101.427314][ T599] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000009: 0000 [#1] SMP KASAN NOPTI [ 101.427755][ T599] KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f] [ 101.428048][ T599] CPU: 2 UID: 0 PID: 599 Comm: ping Not tainted 7.1.0-rc5-00284-gbce53c430ed7 #102 PREEMPT(full) [ 101.428400][ T599] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 101.428608][ T599] RIP: 0010:qfq_dequeue (net/sched/sch_qfq.c:1150) sch_qfq [ 101.428821][ T599] Code: 00 fc ff df 80 3c 02 00 0f 85 46 0c 00 00 4c 8d 73 48 48 89 9d b8 02 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 f2 48 c1 ea 03 <80> 3c 02 00 0f 85 2d 0c 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b All code [ 101.429348][ T599] RSP: 0018:ffff8881110df4f0 EFLAGS: 00010216 [ 101.429541][ T599] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: dffffc0000000000 [ 101.429763][ T599] RDX: 0000000000000009 RSI: 00000024c0000000 RDI: ffff88811436c2b0 [ 101.429985][ T599] RBP: ffff88811436c000 R08: ffff88811436c280 R09: 1ffff11021277523 [ 101.430206][ T599] R10: 1ffff11021277526 R11: 1ffff11021277527 R12: 00000024c0000000 [ 101.430423][ T599] R13: ffff88811436c2b8 R14: 0000000000000048 R15: 0000000020000000 [ 101.430642][ T599] FS: 00007f61813e1c40(0000) GS:ffff8881691ef000(0000) knlGS:0000000000000000 [ 101.430913][ T599] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 101.431100][ T599] CR2: 00005651650850a8 CR3: 000000010ca0b000 CR4: 0000000000750ef0 [ 101.431320][ T599] PKRU: 55555554 [ 101.431433][ T599] Call Trace: [ 101.431544][ T599] <TASK> [ 101.431628][ T599] __qdisc_run (net/sched/sch_generic.c:322 net/sched/sch_generic.c:427 net/sched/sch_generic.c:445) [ 101.431792][ T599] ? dev_qdisc_enqueue (./include/trace/events/qdisc.h:49 (discriminator 22) net/core/dev.c:4176 (discriminator 22)) [ 101.431941][ T599] __dev_queue_xmit (./include/net/pkt_sched.h:120 ./include/net/pkt_sched.h:117 net/core/dev.c:4292 net/core/dev.c:4831) Fix this by only calling qdisc_tree_reduce_backlog in peek after the qlen is restored.
CVE-2026-74342 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: kernfs: link kn to its parent before the LSM init hook After commit 12e9e3cd03b5 ("simpe_xattr: use per-sb cache"), kernfs_xattr_set() and kernfs_xattr_get() compute the cache via kernfs_root(kn) before any other check. kernfs_root(kn) walks kn->__parent first and falls back to kn->dir.root, both of which are NULL on a freshly kmem_cache_zalloc()'d kn. kn->__parent was being set in kernfs_new_node() after __kernfs_new_node() returned, and kn->dir.root is set even later by kernfs_create_dir_ns() / kernfs_create_empty_dir(). The LSM kernfs_init_security hook is invoked from inside __kernfs_new_node(), before either field has been initialized. selinux_kernfs_init_security() ends with kernfs_xattr_set(kn, XATTR_NAME_SELINUX, ...). kernfs_root(kn) then returns NULL, and &((struct kernfs_root *)NULL)->xa_cache evaluates to offsetof(struct kernfs_root, xa_cache) which faults: BUG: kernel NULL pointer dereference, address: 00000000000000e0 RIP: 0010:simple_xattr_set+0x27/0x8b0 Call Trace: kernfs_xattr_set+0x63/0xb0 selinux_kernfs_init_security+0x13b/0x270 security_kernfs_init_security+0x36/0xc0 __kernfs_new_node+0x182/0x290 kernfs_new_node+0x80/0xc0 kernfs_create_dir_ns+0x2b/0xa0 cgroup_create+0x116/0x380 cgroup_mkdir+0x7c/0x1a0 Reproduces deterministically at PID 1 (systemd) on an SELinux-enabled distro. The first cgroup mkdir under /sys/fs/cgroup with a labelled parent panics the kernel. The LSM hook's contract is that the kn_dir argument is the parent of the new kn, so kn->__parent should already point at kn_dir when the hook runs. Move kernfs_get(parent) and rcu_assign_pointer of kn->__parent from kernfs_new_node() into __kernfs_new_node() right before the security hook, and unwind the parent reference on the err_out4 path. kernfs_root(kn) then takes its parent branch during the hook and returns parent->dir.root, which is the correct root. This also closes the same-shape latent bug in kernfs_xattr_get() (which today is hidden only by kernfs_iattrs_noalloc() returning NULL on a fresh kn).
CVE-2026-74435 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: rxrpc: rxrpc_verify_data ensure rx_dec_buffer alloc rxrpc_recvmsg_data() calls rxrpc_verify_data() whenever the rxrpc_call.rx_dec_buffer is unallocated and assumes that upon successful return that rx_dec_buffer must be allocated. However, rxrpc_verify_data() does not request an allocation if the rxrpc_skb_priv.len is zero. In addition, failure to allocate rx_dec_buffer will result in a call to skb_copy_bits() with a NULL destination which can trigger a NULL pointer dereference. To prevent these issues rxrpc_verify_data() is modified to always attempt to allocate the rxrpc_call.rx_dec_buffer if it is NULL. This issue was identified with assistance of a private sashiko instance.
CVE-2026-74321 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs() In the beginning of the loop, we try to obtain a locked delayed ref head, if 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(), which can return an error pointer. If the error pointer is -EAGAIN we do a continue and go back to the beginning of the loop, which will not try again to call btrfs_select_ref_head() since 'locked_ref' is no longer NULL but it's ERR_PTR(-EAGAIN), and then we do: spin_lock(&locked_ref->lock); against a ERR_PTR(-EAGAIN) value, generating an invalid pointer dereference. Fix this by ensuring that 'locked_ref' is set to NULL when btrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count' as well, to prevent infinite looping. We do this by doing a goto to the bottom of the loop that already sets 'locked_ref' to NULL and does a cond_resched(), with an increment to 'count' right before the goto. These measures were in place before the refactoring in commit 0110a4c43451 ("btrfs: refactor __btrfs_run_delayed_refs loop") but were unintentionally lost afterwards.
CVE-2026-74335 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix NULL pointer dereference in bpf_task_from_vpid() bpf_task_from_vpid() looks up a task in the pid namespace of the current task, via find_task_by_vpid(): find_task_by_vpid(vpid) find_task_by_pid_ns(vpid, task_active_pid_ns(current)) find_pid_ns(nr, ns) -> idr_find(&ns->idr, nr) cgroup_skb programs run in softirq, which may interrupt a task that is itself in do_exit(). Once that task has passed exit_notify() -> release_task() -> __unhash_process(), its thread_pid is cleared, so task_active_pid_ns(current) returns NULL and find_pid_ns() dereferences &NULL->idr: BUG: kernel NULL pointer dereference, address: 0000000000000050 RIP: 0010:idr_find+0x11/0x30 lib/idr.c:176 Call Trace: <IRQ> find_pid_ns kernel/pid.c:370 [inline] find_task_by_pid_ns+0x3b/0xe0 kernel/pid.c:485 bpf_task_from_vpid+0x5b/0x200 kernel/bpf/helpers.c:2916 bpf_prog_run_array_cg+0x17e/0x530 kernel/bpf/cgroup.c:81 __cgroup_bpf_run_filter_skb+0x12b/0x250 kernel/bpf/cgroup.c:1612 sk_filter_trim_cap+0x1dc/0x4c0 net/core/filter.c:148 tcp_v4_rcv+0x18d1/0x2200 net/ipv4/tcp_ipv4.c:2223 </IRQ> <TASK> do_exit+0xa63/0x1270 kernel/exit.c:1010 get_signal+0x141c/0x1530 kernel/signal.c:3037 Bail out when current has no pid namespace.
CVE-2026-74424 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: fbcon: fix NULL pointer dereference for a console without vc_data fbcon_new_modelist() runs when a framebuffer's modelist changes. For each console mapped to it with fb_display[i].mode set, it reads vc_cons[i].d and passes the vc_num to fbcon_set_disp(). This assumes a console with a mode set has a vc_data, but it can be NULL. fbcon_set_disp() sets fb_display[i].mode before it checks vc_data, and fbcon_deinit() leaves the mode set after the vc_data is freed. fbcon_new_modelist() then dereferences the NULL vc_data. Keep fb_display[i].mode set only while the console has a vc_data. Check vc_data before setting the mode in fbcon_set_disp(), and clear the mode in fbcon_deinit(). The existing mode check in fbcon_new_modelist() then skips such consoles.
CVE-2026-74571 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: btrfs: skip global block reserve accounting for rescue mounts [BUG] Mounting with rescue=ibadroots after corrupting the block group tree root triggers a NULL pointer dereference: BUG: kernel NULL pointer dereference, address: 0000000000000100 RIP: 0010:btrfs_update_global_block_rsv+0x9d/0x1c0 [btrfs] Call Trace: fill_dummy_bgs+0xd4/0x120 [btrfs] open_ctree+0xc6e/0x1ca0 [btrfs] btrfs_get_tree+0x50d/0xa40 [btrfs] The same crash occurs with a corrupted raid stripe tree root, via btrfs_read_block_groups() instead of fill_dummy_bgs(). [CAUSE] With rescue=ibadroots, btrfs_read_roots() allows the mount to continue when either root cannot be read, leaving the corresponding root pointer NULL while its on-disk feature bit remains set. btrfs_update_global_block_rsv() then dereferences the missing root based on the feature bit alone. [FIX] Rescue mounts are fully read-only and cannot start transactions, so the global reserve is never consumed. Under btrfs_is_full_ro(), mark the reserve as full and return before performing the accounting. And since we need to check if the fs is mount fully RO, export fs_is_full_ro() as btrfs_is_full_ro(), and move it to fs.h. [ Squash the fs_is_full_ro() export commit into this one. ]
CVE-2026-74552 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: hwmon: (lm90) Only report alarms if driver is ready Userspace can read sysfs attributes before driver registration is complete, immediately after devm_hwmon_device_register_with_info() has been called. At that time, data->hwmon_dev is not yet initialized. This can trigger a NULL pointer access since lm90_update_device() and with it lm90_update_alarms_locked() will be called. This call schedules report_work and lm90_report_alarms(), which passes the still-NULL data->hwmon_dev to hwmon_notify_event() and triggers a NULL pointer dereference. Fix the problem by only scheduling the report and alert workers data->hwmon_dev is set.
CVE-2026-74530 1 Linux 1 Linux Kernel 2026-08-15 N/A
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_sync: hold conn in hci_connect_big_sync() callback There is theoretical UAF if the conn is freed while the hci_sync task is running. Hold refcount to avoid that. Handle NULL hcon, return 0 + do nothing to match the previous behavior.