In the Linux kernel, the following vulnerability has been resolved: bpf: Use raw_spinlock_t in ringbuf The function __bpf_ringbuf_reserve is invoked from a tracepoint, which disables preemption. Using spinlock_t in this context can lead to a "sleep in atomic" warning in the RT variant. This issue is illustrated in the example below: BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 556208, name: test_progs preempt_count: 1, expected: 0 RCU nest depth: 1, expected: 1 INFO: lockdep is turned off. Preemption disabled at: [<ffffd33a5c88ea44>] migrate_enable+0xc0/0x39c CPU: 7 PID: 556208 Comm: test_progs Tainted: G Hardware name: Qualcomm SA8775P Ride (DT) Call trace: dump_backtrace+0xac/0x130 show_stack+0x1c/0x30 dump_stack_lvl+0xac/0xe8 dump_stack+0x18/0x30 __might_resched+0x3bc/0x4fc rt_spin_lock+0x8c/0x1a4 __bpf_ringbuf_reserve+0xc4/0x254 bpf_ringbuf_reserve_dynptr+0x5c/0xdc bpf_prog_ac3d15160d62622a_test_read_write+0x104/0x238 trace_call_bpf+0x238/0x774 perf_call_bpf_enter.isra.0+0x104/0x194 perf_syscall_enter+0x2f8/0x510 trace_sys_enter+0x39c/0x564 syscall_trace_enter+0x220/0x3c0 do_el0_svc+0x138/0x1dc el0_svc+0x54/0x130 el0t_64_sync_handler+0x134/0x150 el0t_64_sync+0x17c/0x180 Switch the spinlock to raw_spinlock_t to avoid this error.

In the Linux kernel, the following vulnerability has been resolved: reset: starfive: jh71x0: Fix accessing the empty member on JH7110 SoC data->asserted will be NULL on JH7110 SoC since commit 82327b127d41 ("reset: starfive: Add StarFive JH7110 reset driver") was added. Add the judgment condition to avoid errors when calling reset_control_status on JH7110 SoC.

In the Linux kernel, the following vulnerability has been resolved: net/mlx5: Unregister notifier on eswitch init failure It otherwise remains registered and a subsequent attempt at eswitch enabling might trigger warnings of the sort: [ 682.589148] ------------[ cut here ]------------ [ 682.590204] notifier callback eswitch_vport_event [mlx5_core] already registered [ 682.590256] WARNING: CPU: 13 PID: 2660 at kernel/notifier.c:31 notifier_chain_register+0x3e/0x90 [...snipped] [ 682.610052] Call Trace: [ 682.610369] <TASK> [ 682.610663] ? __warn+0x7c/0x110 [ 682.611050] ? notifier_chain_register+0x3e/0x90 [ 682.611556] ? report_bug+0x148/0x170 [ 682.611977] ? handle_bug+0x36/0x70 [ 682.612384] ? exc_invalid_op+0x13/0x60 [ 682.612817] ? asm_exc_invalid_op+0x16/0x20 [ 682.613284] ? notifier_chain_register+0x3e/0x90 [ 682.613789] atomic_notifier_chain_register+0x25/0x40 [ 682.614322] mlx5_eswitch_enable_locked+0x1d4/0x3b0 [mlx5_core] [ 682.614965] mlx5_eswitch_enable+0xc9/0x100 [mlx5_core] [ 682.615551] mlx5_device_enable_sriov+0x25/0x340 [mlx5_core] [ 682.616170] mlx5_core_sriov_configure+0x50/0x170 [mlx5_core] [ 682.616789] sriov_numvfs_store+0xb0/0x1b0 [ 682.617248] kernfs_fop_write_iter+0x117/0x1a0 [ 682.617734] vfs_write+0x231/0x3f0 [ 682.618138] ksys_write+0x63/0xe0 [ 682.618536] do_syscall_64+0x4c/0x100 [ 682.618958] entry_SYSCALL_64_after_hwframe+0x4b/0x53

In the Linux kernel, the following vulnerability has been resolved: nvme-pci: fix race condition between reset and nvme_dev_disable() nvme_dev_disable() modifies the dev->online_queues field, therefore nvme_pci_update_nr_queues() should avoid racing against it, otherwise we could end up passing invalid values to blk_mq_update_nr_hw_queues(). WARNING: CPU: 39 PID: 61303 at drivers/pci/msi/api.c:347 pci_irq_get_affinity+0x187/0x210 Workqueue: nvme-reset-wq nvme_reset_work [nvme] RIP: 0010:pci_irq_get_affinity+0x187/0x210 Call Trace: <TASK> ? blk_mq_pci_map_queues+0x87/0x3c0 ? pci_irq_get_affinity+0x187/0x210 blk_mq_pci_map_queues+0x87/0x3c0 nvme_pci_map_queues+0x189/0x460 [nvme] blk_mq_update_nr_hw_queues+0x2a/0x40 nvme_reset_work+0x1be/0x2a0 [nvme] Fix the bug by locking the shutdown_lock mutex before using dev->online_queues. Give up if nvme_dev_disable() is running or if it has been executed already.

In the Linux kernel, the following vulnerability has been resolved: drm/vboxvideo: Replace fake VLA at end of vbva_mouse_pointer_shape with real VLA Replace the fake VLA at end of the vbva_mouse_pointer_shape shape with a real VLA to fix a "memcpy: detected field-spanning write error" warning: [ 13.319813] memcpy: detected field-spanning write (size 16896) of single field "p->data" at drivers/gpu/drm/vboxvideo/hgsmi_base.c:154 (size 4) [ 13.319841] WARNING: CPU: 0 PID: 1105 at drivers/gpu/drm/vboxvideo/hgsmi_base.c:154 hgsmi_update_pointer_shape+0x192/0x1c0 [vboxvideo] [ 13.320038] Call Trace: [ 13.320173] hgsmi_update_pointer_shape [vboxvideo] [ 13.320184] vbox_cursor_atomic_update [vboxvideo] Note as mentioned in the added comment it seems the original length calculation for the allocated and send hgsmi buffer is 4 bytes too large. Changing this is not the goal of this patch, so this behavior is kept.

In the Linux kernel, the following vulnerability has been resolved: LoongArch: Don't crash in stack_top() for tasks without vDSO Not all tasks have a vDSO mapped, for example kthreads never do. If such a task ever ends up calling stack_top(), it will derefence the NULL vdso pointer and crash. This can for example happen when using kunit: [<9000000000203874>] stack_top+0x58/0xa8 [<90000000002956cc>] arch_pick_mmap_layout+0x164/0x220 [<90000000003c284c>] kunit_vm_mmap_init+0x108/0x12c [<90000000003c1fbc>] __kunit_add_resource+0x38/0x8c [<90000000003c2704>] kunit_vm_mmap+0x88/0xc8 [<9000000000410b14>] usercopy_test_init+0xbc/0x25c [<90000000003c1db4>] kunit_try_run_case+0x5c/0x184 [<90000000003c3d54>] kunit_generic_run_threadfn_adapter+0x24/0x48 [<900000000022e4bc>] kthread+0xc8/0xd4 [<9000000000200ce8>] ret_from_kernel_thread+0xc/0xa4

In the Linux kernel, the following vulnerability has been resolved: tracing/probes: Fix MAX_TRACE_ARGS limit handling When creating a trace_probe we would set nr_args prior to truncating the arguments to MAX_TRACE_ARGS. However, we would only initialize arguments up to the limit. This caused invalid memory access when attempting to set up probes with more than 128 fetchargs. BUG: kernel NULL pointer dereference, address: 0000000000000020 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 UID: 0 PID: 1769 Comm: cat Not tainted 6.11.0-rc7+ #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014 RIP: 0010:__set_print_fmt+0x134/0x330 Resolve the issue by applying the MAX_TRACE_ARGS limit earlier. Return an error when there are too many arguments instead of silently truncating.

In the Linux kernel, the following vulnerability has been resolved: tracing: Consider the NULL character when validating the event length strlen() returns a string length excluding the null byte. If the string length equals to the maximum buffer length, the buffer will have no space for the NULL terminating character. This commit checks this condition and returns failure for it.

In the Linux kernel, the following vulnerability has been resolved: netfilter: bpf: must hold reference on net namespace BUG: KASAN: slab-use-after-free in __nf_unregister_net_hook+0x640/0x6b0 Read of size 8 at addr ffff8880106fe400 by task repro/72= bpf_nf_link_release+0xda/0x1e0 bpf_link_free+0x139/0x2d0 bpf_link_release+0x68/0x80 __fput+0x414/0xb60 Eric says: It seems that bpf was able to defer the __nf_unregister_net_hook() after exit()/close() time. Perhaps a netns reference is missing, because the netns has been dismantled/freed already. bpf_nf_link_attach() does : link->net = net; But I do not see a reference being taken on net. Add such a reference and release it after hook unreg. Note that I was unable to get syzbot reproducer to work, so I do not know if this resolves this splat.

In the Linux kernel, the following vulnerability has been resolved: net: pse-pd: Fix out of bound for loop Adjust the loop limit to prevent out-of-bounds access when iterating over PI structures. The loop should not reach the index pcdev->nr_lines since we allocate exactly pcdev->nr_lines number of PI structures. This fix ensures proper bounds are maintained during iterations.

In the Linux kernel, the following vulnerability has been resolved: net: wwan: fix global oob in wwan_rtnl_policy The variable wwan_rtnl_link_ops assign a *bigger* maxtype which leads to a global out-of-bounds read when parsing the netlink attributes. Exactly same bug cause as the oob fixed in commit b33fb5b801c6 ("net: qualcomm: rmnet: fix global oob in rmnet_policy"). ================================================================== BUG: KASAN: global-out-of-bounds in validate_nla lib/nlattr.c:388 [inline] BUG: KASAN: global-out-of-bounds in __nla_validate_parse+0x19d7/0x29a0 lib/nlattr.c:603 Read of size 1 at addr ffffffff8b09cb60 by task syz.1.66276/323862 CPU: 0 PID: 323862 Comm: syz.1.66276 Not tainted 6.1.70 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x177/0x231 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:284 [inline] print_report+0x14f/0x750 mm/kasan/report.c:395 kasan_report+0x139/0x170 mm/kasan/report.c:495 validate_nla lib/nlattr.c:388 [inline] __nla_validate_parse+0x19d7/0x29a0 lib/nlattr.c:603 __nla_parse+0x3c/0x50 lib/nlattr.c:700 nla_parse_nested_deprecated include/net/netlink.h:1269 [inline] __rtnl_newlink net/core/rtnetlink.c:3514 [inline] rtnl_newlink+0x7bc/0x1fd0 net/core/rtnetlink.c:3623 rtnetlink_rcv_msg+0x794/0xef0 net/core/rtnetlink.c:6122 netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2508 netlink_unicast_kernel net/netlink/af_netlink.c:1326 [inline] netlink_unicast+0x74b/0x8c0 net/netlink/af_netlink.c:1352 netlink_sendmsg+0x882/0xb90 net/netlink/af_netlink.c:1874 sock_sendmsg_nosec net/socket.c:716 [inline] __sock_sendmsg net/socket.c:728 [inline] ____sys_sendmsg+0x5cc/0x8f0 net/socket.c:2499 ___sys_sendmsg+0x21c/0x290 net/socket.c:2553 __sys_sendmsg net/socket.c:2582 [inline] __do_sys_sendmsg net/socket.c:2591 [inline] __se_sys_sendmsg+0x19e/0x270 net/socket.c:2589 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x45/0x90 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f67b19a24ad RSP: 002b:00007f67b17febb8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f67b1b45f80 RCX: 00007f67b19a24ad RDX: 0000000000000000 RSI: 0000000020005e40 RDI: 0000000000000004 RBP: 00007f67b1a1e01d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffd2513764f R14: 00007ffd251376e0 R15: 00007f67b17fed40 </TASK> The buggy address belongs to the variable: wwan_rtnl_policy+0x20/0x40 The buggy address belongs to the physical page: page:ffffea00002c2700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xb09c flags: 0xfff00000001000(reserved|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000001000 ffffea00002c2708 ffffea00002c2708 0000000000000000 raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner info is not present (never set?) Memory state around the buggy address: ffffffff8b09ca00: 05 f9 f9 f9 05 f9 f9 f9 00 01 f9 f9 00 01 f9 f9 ffffffff8b09ca80: 00 00 00 05 f9 f9 f9 f9 00 00 03 f9 f9 f9 f9 f9 >ffffffff8b09cb00: 00 00 00 00 05 f9 f9 f9 00 00 00 00 f9 f9 f9 f9 ^ ffffffff8b09cb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ================================================================== According to the comment of `nla_parse_nested_deprecated`, use correct size `IFLA_WWAN_MAX` here to fix this issue.

In the Linux kernel, the following vulnerability has been resolved: net: sched: fix use-after-free in taprio_change() In 'taprio_change()', 'admin' pointer may become dangling due to sched switch / removal caused by 'advance_sched()', and critical section protected by 'q->current_entry_lock' is too small to prevent from such a scenario (which causes use-after-free detected by KASAN). Fix this by prefer 'rcu_replace_pointer()' over 'rcu_assign_pointer()' to update 'admin' immediately before an attempt to schedule freeing.

In the Linux kernel, the following vulnerability has been resolved: net: sched: use RCU read-side critical section in taprio_dump() Fix possible use-after-free in 'taprio_dump()' by adding RCU read-side critical section there. Never seen on x86 but found on a KASAN-enabled arm64 system when investigating https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa: [T15862] BUG: KASAN: slab-use-after-free in taprio_dump+0xa0c/0xbb0 [T15862] Read of size 4 at addr ffff0000d4bb88f8 by task repro/15862 [T15862] [T15862] CPU: 0 UID: 0 PID: 15862 Comm: repro Not tainted 6.11.0-rc1-00293-gdefaf1a2113a-dirty #2 [T15862] Hardware name: QEMU QEMU Virtual Machine, BIOS edk2-20240524-5.fc40 05/24/2024 [T15862] Call trace: [T15862] dump_backtrace+0x20c/0x220 [T15862] show_stack+0x2c/0x40 [T15862] dump_stack_lvl+0xf8/0x174 [T15862] print_report+0x170/0x4d8 [T15862] kasan_report+0xb8/0x1d4 [T15862] __asan_report_load4_noabort+0x20/0x2c [T15862] taprio_dump+0xa0c/0xbb0 [T15862] tc_fill_qdisc+0x540/0x1020 [T15862] qdisc_notify.isra.0+0x330/0x3a0 [T15862] tc_modify_qdisc+0x7b8/0x1838 [T15862] rtnetlink_rcv_msg+0x3c8/0xc20 [T15862] netlink_rcv_skb+0x1f8/0x3d4 [T15862] rtnetlink_rcv+0x28/0x40 [T15862] netlink_unicast+0x51c/0x790 [T15862] netlink_sendmsg+0x79c/0xc20 [T15862] __sock_sendmsg+0xe0/0x1a0 [T15862] ____sys_sendmsg+0x6c0/0x840 [T15862] ___sys_sendmsg+0x1ac/0x1f0 [T15862] __sys_sendmsg+0x110/0x1d0 [T15862] __arm64_sys_sendmsg+0x74/0xb0 [T15862] invoke_syscall+0x88/0x2e0 [T15862] el0_svc_common.constprop.0+0xe4/0x2a0 [T15862] do_el0_svc+0x44/0x60 [T15862] el0_svc+0x50/0x184 [T15862] el0t_64_sync_handler+0x120/0x12c [T15862] el0t_64_sync+0x190/0x194 [T15862] [T15862] Allocated by task 15857: [T15862] kasan_save_stack+0x3c/0x70 [T15862] kasan_save_track+0x20/0x3c [T15862] kasan_save_alloc_info+0x40/0x60 [T15862] __kasan_kmalloc+0xd4/0xe0 [T15862] __kmalloc_cache_noprof+0x194/0x334 [T15862] taprio_change+0x45c/0x2fe0 [T15862] tc_modify_qdisc+0x6a8/0x1838 [T15862] rtnetlink_rcv_msg+0x3c8/0xc20 [T15862] netlink_rcv_skb+0x1f8/0x3d4 [T15862] rtnetlink_rcv+0x28/0x40 [T15862] netlink_unicast+0x51c/0x790 [T15862] netlink_sendmsg+0x79c/0xc20 [T15862] __sock_sendmsg+0xe0/0x1a0 [T15862] ____sys_sendmsg+0x6c0/0x840 [T15862] ___sys_sendmsg+0x1ac/0x1f0 [T15862] __sys_sendmsg+0x110/0x1d0 [T15862] __arm64_sys_sendmsg+0x74/0xb0 [T15862] invoke_syscall+0x88/0x2e0 [T15862] el0_svc_common.constprop.0+0xe4/0x2a0 [T15862] do_el0_svc+0x44/0x60 [T15862] el0_svc+0x50/0x184 [T15862] el0t_64_sync_handler+0x120/0x12c [T15862] el0t_64_sync+0x190/0x194 [T15862] [T15862] Freed by task 6192: [T15862] kasan_save_stack+0x3c/0x70 [T15862] kasan_save_track+0x20/0x3c [T15862] kasan_save_free_info+0x4c/0x80 [T15862] poison_slab_object+0x110/0x160 [T15862] __kasan_slab_free+0x3c/0x74 [T15862] kfree+0x134/0x3c0 [T15862] taprio_free_sched_cb+0x18c/0x220 [T15862] rcu_core+0x920/0x1b7c [T15862] rcu_core_si+0x10/0x1c [T15862] handle_softirqs+0x2e8/0xd64 [T15862] __do_softirq+0x14/0x20

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: SCO: Fix UAF on sco_sock_timeout conn->sk maybe have been unlinked/freed while waiting for sco_conn_lock so this checks if the conn->sk is still valid by checking if it part of sco_sk_list.

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: ISO: Fix UAF on iso_sock_timeout conn->sk maybe have been unlinked/freed while waiting for iso_conn_lock so this checks if the conn->sk is still valid by checking if it part of iso_sk_list.

In the Linux kernel, the following vulnerability has been resolved: bpf: Add the missing BPF_LINK_TYPE invocation for sockmap There is an out-of-bounds read in bpf_link_show_fdinfo() for the sockmap link fd. Fix it by adding the missing BPF_LINK_TYPE invocation for sockmap link Also add comments for bpf_link_type to prevent missing updates in the future.

In the Linux kernel, the following vulnerability has been resolved: nfsd: cancel nfsd_shrinker_work using sync mode in nfs4_state_shutdown_net In the normal case, when we excute `echo 0 > /proc/fs/nfsd/threads`, the function `nfs4_state_destroy_net` in `nfs4_state_shutdown_net` will release all resources related to the hashed `nfs4_client`. If the `nfsd_client_shrinker` is running concurrently, the `expire_client` function will first unhash this client and then destroy it. This can lead to the following warning. Additionally, numerous use-after-free errors may occur as well. nfsd_client_shrinker echo 0 > /proc/fs/nfsd/threads expire_client nfsd_shutdown_net unhash_client ... nfs4_state_shutdown_net /* won't wait shrinker exit */ /* cancel_work(&nn->nfsd_shrinker_work) * nfsd_file for this /* won't destroy unhashed client1 */ * client1 still alive nfs4_state_destroy_net */ nfsd_file_cache_shutdown /* trigger warning */ kmem_cache_destroy(nfsd_file_slab) kmem_cache_destroy(nfsd_file_mark_slab) /* release nfsd_file and mark */ __destroy_client ==================================================================== BUG nfsd_file (Not tainted): Objects remaining in nfsd_file on __kmem_cache_shutdown() -------------------------------------------------------------------- CPU: 4 UID: 0 PID: 764 Comm: sh Not tainted 6.12.0-rc3+ #1 dump_stack_lvl+0x53/0x70 slab_err+0xb0/0xf0 __kmem_cache_shutdown+0x15c/0x310 kmem_cache_destroy+0x66/0x160 nfsd_file_cache_shutdown+0xac/0x210 [nfsd] nfsd_destroy_serv+0x251/0x2a0 [nfsd] nfsd_svc+0x125/0x1e0 [nfsd] write_threads+0x16a/0x2a0 [nfsd] nfsctl_transaction_write+0x74/0xa0 [nfsd] vfs_write+0x1a5/0x6d0 ksys_write+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e ==================================================================== BUG nfsd_file_mark (Tainted: G B W ): Objects remaining nfsd_file_mark on __kmem_cache_shutdown() -------------------------------------------------------------------- dump_stack_lvl+0x53/0x70 slab_err+0xb0/0xf0 __kmem_cache_shutdown+0x15c/0x310 kmem_cache_destroy+0x66/0x160 nfsd_file_cache_shutdown+0xc8/0x210 [nfsd] nfsd_destroy_serv+0x251/0x2a0 [nfsd] nfsd_svc+0x125/0x1e0 [nfsd] write_threads+0x16a/0x2a0 [nfsd] nfsctl_transaction_write+0x74/0xa0 [nfsd] vfs_write+0x1a5/0x6d0 ksys_write+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e To resolve this issue, cancel `nfsd_shrinker_work` using synchronous mode in nfs4_state_shutdown_net.

In the Linux kernel, the following vulnerability has been resolved: smb: client: Handle kstrdup failures for passwords In smb3_reconfigure(), after duplicating ctx->password and ctx->password2 with kstrdup(), we need to check for allocation failures. If ses->password allocation fails, return -ENOMEM. If ses->password2 allocation fails, free ses->password, set it to NULL, and return -ENOMEM.

In the Linux kernel, the following vulnerability has been resolved: cifs: fix warning when destroy 'cifs_io_request_pool' There's a issue as follows: WARNING: CPU: 1 PID: 27826 at mm/slub.c:4698 free_large_kmalloc+0xac/0xe0 RIP: 0010:free_large_kmalloc+0xac/0xe0 Call Trace: <TASK> ? __warn+0xea/0x330 mempool_destroy+0x13f/0x1d0 init_cifs+0xa50/0xff0 [cifs] do_one_initcall+0xdc/0x550 do_init_module+0x22d/0x6b0 load_module+0x4e96/0x5ff0 init_module_from_file+0xcd/0x130 idempotent_init_module+0x330/0x620 __x64_sys_finit_module+0xb3/0x110 do_syscall_64+0xc1/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Obviously, 'cifs_io_request_pool' is not created by mempool_create(). So just use mempool_exit() to revert 'cifs_io_request_pool'.

In the Linux kernel, the following vulnerability has been resolved: btrfs: reject ro->rw reconfiguration if there are hard ro requirements [BUG] Syzbot reports the following crash: BTRFS info (device loop0 state MCS): disabling free space tree BTRFS info (device loop0 state MCS): clearing compat-ro feature flag for FREE_SPACE_TREE (0x1) BTRFS info (device loop0 state MCS): clearing compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2) Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:backup_super_roots fs/btrfs/disk-io.c:1691 [inline] RIP: 0010:write_all_supers+0x97a/0x40f0 fs/btrfs/disk-io.c:4041 Call Trace: <TASK> btrfs_commit_transaction+0x1eae/0x3740 fs/btrfs/transaction.c:2530 btrfs_delete_free_space_tree+0x383/0x730 fs/btrfs/free-space-tree.c:1312 btrfs_start_pre_rw_mount+0xf28/0x1300 fs/btrfs/disk-io.c:3012 btrfs_remount_rw fs/btrfs/super.c:1309 [inline] btrfs_reconfigure+0xae6/0x2d40 fs/btrfs/super.c:1534 btrfs_reconfigure_for_mount fs/btrfs/super.c:2020 [inline] btrfs_get_tree_subvol fs/btrfs/super.c:2079 [inline] btrfs_get_tree+0x918/0x1920 fs/btrfs/super.c:2115 vfs_get_tree+0x90/0x2b0 fs/super.c:1800 do_new_mount+0x2be/0xb40 fs/namespace.c:3472 do_mount fs/namespace.c:3812 [inline] __do_sys_mount fs/namespace.c:4020 [inline] __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3997 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f [CAUSE] To support mounting different subvolume with different RO/RW flags for the new mount APIs, btrfs introduced two workaround to support this feature: - Skip mount option/feature checks if we are mounting a different subvolume - Reconfigure the fs to RW if the initial mount is RO Combining these two, we can have the following sequence: - Mount the fs ro,rescue=all,clear_cache,space_cache=v1 rescue=all will mark the fs as hard read-only, so no v2 cache clearing will happen. - Mount a subvolume rw of the same fs. We go into btrfs_get_tree_subvol(), but fc_mount() returns EBUSY because our new fc is RW, different from the original fs. Now we enter btrfs_reconfigure_for_mount(), which switches the RO flag first so that we can grab the existing fs_info. Then we reconfigure the fs to RW. - During reconfiguration, option/features check is skipped This means we will restart the v2 cache clearing, and convert back to v1 cache. This will trigger fs writes, and since the original fs has "rescue=all" option, it skips the csum tree read. And eventually causing NULL pointer dereference in super block writeback. [FIX] For reconfiguration caused by different subvolume RO/RW flags, ensure we always run btrfs_check_options() to ensure we have proper hard RO requirements met. In fact the function btrfs_check_options() doesn't really do many complex checks, but hard RO requirement and some feature dependency checks, thus there is no special reason not to do the check for mount reconfiguration.