CVE-2021-47656

The Linux Kernel, the operating system core itself.

Security Fix(es):

In the Linux kernel, the following vulnerability has been resolved:

ubi: Fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl

Hulk Robot reported a KASAN report about use-after-free:

BUG: KASAN: use-after-free in __list_del_entry_valid+0x13d/0x160 Read of size 8 at addr ffff888035e37d98 by task ubiattach/1385 [...] Call Trace: klist_dec_and_del+0xa7/0x4a0 klist_put+0xc7/0x1a0 device_del+0x4d4/0xed0 cdev_device_del+0x1a/0x80 ubi_attach_mtd_dev+0x2951/0x34b0 [ubi] ctrl_cdev_ioctl+0x286/0x2f0 [ubi]

Allocated by task 1414: device_add+0x60a/0x18b0 cdev_device_add+0x103/0x170 ubi_create_volume+0x1118/0x1a10 [ubi] ubi_cdev_ioctl+0xb7f/0x1ba0 [ubi]

Freed by task 1385: cdev_device_del+0x1a/0x80 ubi_remove_volume+0x438/0x6c0 [ubi] ubi_cdev_ioctl+0xbf4/0x1ba0 [ubi] [...]

The lock held by ctrl_cdev_ioctl is ubi_devices_mutex, but the lock held by ubi_cdev_ioctl is ubi->device_mutex. Therefore, the two locks can be concurrent.

ctrl_cdev_ioctl contains two operations: ubi_attach and ubi_detach. ubi_detach is bug-free because it uses reference counting to prevent concurrency. However, uif_init and uif_close in ubi_attach may race with ubi_cdev_ioctl.

uif_init will race with ubi_cdev_ioctl as in the following stack. cpu1 cpu2 cpu3 ||_____________________ ctrl_cdev_ioctl ubi_attach_mtd_dev uif_init ubi_cdev_ioctl ubi_create_volume cdev_device_add ubi_add_volume // sysfs exist kill_volumes ubi_cdev_ioctl ubi_remove_volume cdev_device_del // first free ubi_free_volume cdev_del // double free cdev_device_del

And uif_close will race with ubi_cdev_ioctl as in the following stack. cpu1 cpu2 cpu3 ||_____________________ ctrl_cdev_ioctl ubi_attach_mtd_dev uif_init ubi_cdev_ioctl ubi_create_volume cdev_device_add ubi_debugfs_init_dev //error goto out_uif; uif_close kill_volumes ubi_cdev_ioctl ubi_remove_volume cdev_device_del // first free ubi_free_volume // double free

The cause of this problem is that commit 714fb87e8bc0 make device "available" before it becomes accessible via sysfs. Therefore, we roll back the modification. We will fix the race condition between ubi device creation and udev by removing ubi_get_device in vol_attribute_show and dev_attribute_show.This avoids accessing uninitialized ubi_devices[ubi_num].

ubi_get_device is used to prevent devices from being deleted during sysfs execution. However, now kernfs ensures that devices will not be deleted before all reference counting are released. The key process is shown in the following stack.

device_del device_remove_attrs device_remove_groups sysfs_remove_groups sysfs_remove_group remove_files kernfs_remove_by_name kernfs_remove_by_name_ns __kernfs_remove kernfs_drain(CVE-2021-47634)

In the Linux kernel, the following vulnerability has been resolved:

jffs2: fix use-after-free in jffs2_clear_xattr_subsystem …

In the Linux kernel, the following vulnerability has been resolved: jffs2: fix use-after-free in jffs2_clear_xattr_subsystem When we mount a jffs2 image, assume that the first few blocks of the image are normal and contain at least one xattr-related inode, but the next block is abnormal. As a result, an error is returned in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then called in jffs2_build_filesystem() and then again in jffs2_do_fill_super(). Finally we can observe the following report: ================================================================== BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac Read of size 8 at addr ffff8881243384e0 by task mount/719 Call Trace: dump_stack+0x115/0x16b jffs2_clear_xattr_subsystem+0x95/0x6ac jffs2_do_fill_super+0x84f/0xc30 jffs2_fill_super+0x2ea/0x4c0 mtd_get_sb+0x254/0x400 mtd_get_sb_by_nr+0x4f/0xd0 get_tree_mtd+0x498/0x840 jffs2_get_tree+0x25/0x30 vfs_get_tree+0x8d/0x2e0 path_mount+0x50f/0x1e50 do_mount+0x107/0x130 __se_sys_mount+0x1c5/0x2f0 __x64_sys_mount+0xc7/0x160 do_syscall_64+0x45/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Allocated by task 719: kasan_save_stack+0x23/0x60 __kasan_kmalloc.constprop.0+0x10b/0x120 kasan_slab_alloc+0x12/0x20 kmem_cache_alloc+0x1c0/0x870 jffs2_alloc_xattr_ref+0x2f/0xa0 jffs2_scan_medium.cold+0x3713/0x4794 jffs2_do_mount_fs.cold+0xa7/0x2253 jffs2_do_fill_super+0x383/0xc30 jffs2_fill_super+0x2ea/0x4c0 [...] Freed by task 719: kmem_cache_free+0xcc/0x7b0 jffs2_free_xattr_ref+0x78/0x98 jffs2_clear_xattr_subsystem+0xa1/0x6ac jffs2_do_mount_fs.cold+0x5e6/0x2253 jffs2_do_fill_super+0x383/0xc30 jffs2_fill_super+0x2ea/0x4c0 [...] The buggy address belongs to the object at ffff8881243384b8 which belongs to the cache jffs2_xattr_ref of size 48 The buggy address is located 40 bytes inside of 48-byte region [ffff8881243384b8, ffff8881243384e8) [...] ================================================================== The triggering of the BUG is shown in the following stack: ----------------------------------------------------------- jffs2_fill_super jffs2_do_fill_super jffs2_do_mount_fs jffs2_build_filesystem jffs2_scan_medium jffs2_scan_eraseblock <--- ERROR jffs2_clear_xattr_subsystem <--- free jffs2_clear_xattr_subsystem <--- free again ----------------------------------------------------------- An error is returned in jffs2_do_mount_fs(). If the error is returned by jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to be executed. If the error is returned by jffs2_build_filesystem(), the jffs2_clear_xattr_subsystem() also does not need to be executed again. So move jffs2_clear_xattr_subsystem() from 'out_inohash' to 'out_root' to fix this UAF problem.

The SUSE Linux Enterprise 15 SP4 kernel was updated to receive various security bugfixes.

The following security bugs were fixed:

• CVE-2024-2201: Fixed information leak in x86/BHI (bsc#1217339).
• CVE-2024-41092: drm/i915/gt: Fix potential UAF by revoke of fence registers (bsc#1228483).
• CVE-2024-42098: crypto: ecdh - explicitly zeroize private_key (bsc#1228779).
• CVE-2024-42229: crypto: aead,cipher - zeroize key buffer after use (bsc#1228708).
• CVE-2024-57996: net_sched: sch_sfq: do not allow 1 packet limit (bsc#1239076).
• CVE-2024-58014: wifi: brcmsmac: add gain range check to wlc_phy_iqcal_gainparams_nphy() (bsc#1239109).
• CVE-2025-21718: net: rose: fix timer races against user threads (bsc#1239073).
• CVE-2025-21780: drm/amdgpu: avoid buffer overflow attach in smu_sys_set_pp_table() (bsc#1239115).

The following non-security bugs were fixed:

• initcall_blacklist: Does not allow kernel_lockdown be blacklisted (bsc#1237521).
• x86/bhi: Avoid warning in #DB handler due to BHI mitigation (git-fixes).
• x86/bugs: Cache the value of MSR_IA32_ARCH_CAPABILITIES (git-fixes).
• x86/bugs: Fix BHI documentation (git-fixes).
• x86/bugs: Fix BHI handling of RRSBA (git-fixes).
• x86/bugs: Fix BHI retpoline check (git-fixes).
• x86/bugs: Fix return type of spectre_bhi_state() (git-fixes).
• x86/bugs: Remove CONFIG_BHI_MITIGATION_AUTO and spectre_bhi=auto (git-fixes).

The SUSE Linux Enterprise 15 SP5 RT kernel was updated to receive various security bugfixes.

The following security bugs were fixed:

• CVE-2022-49053: scsi: target: tcmu: Fix possible page UAF (bsc#1237918).
• CVE-2022-49465: blk-throttle: Set BIO_THROTTLED when bio has been throttled (bsc#1238919).
• CVE-2022-49739: gfs2: Always check inode size of inline inodes (bsc#1240207).
• CVE-2023-52935: mm/khugepaged: fix ->anon_vma race (bsc#1240276).
• CVE-2024-53124: net: fix data-races around sk->sk_forward_alloc (bsc#1234074).
• CVE-2024-53176: smb: During unmount, ensure all cached dir instances drop their dentry (bsc#1234894).
• CVE-2024-53178: smb: Do not leak cfid when reconnect races with open_cached_dir (bsc#1234895).
• CVE-2024-56651: can: hi311x: hi3110_can_ist(): fix potential use-after-free (bsc#1235528).
• CVE-2024-57996: net_sched: sch_sfq: do not allow 1 packet limit (bsc#1239076).
• CVE-2024-58013: Bluetooth: MGMT: Fix slab-use-after-free Read in mgmt_remove_adv_monitor_sync (bsc#1239095).
• CVE-2024-58014: wifi: brcmsmac: add gain range check to wlc_phy_iqcal_gainparams_nphy() (bsc#1239109).
• CVE-2025-21693: mm: zswap: properly synchronize freeing resources during CPU hotunplug (bsc#1237029).
• CVE-2025-21718: net: rose: fix timer races against user threads (bsc#1239073).
• CVE-2025-21772: partitions: mac: fix handling of bogus partition table (bsc#1238911).
• CVE-2025-21780: drm/amdgpu: avoid buffer overflow attach in smu_sys_set_pp_table() (bsc#1239115).

The following non-security bugs were fixed:

• ACPI: processor: idle: Return an error if both P_LVL{2,3} idle states are invalid (bsc#1237530).
• RDMA/mana_ib: Prefer struct_size over open coded arithmetic (bsc#1239016).
• RDMA/mana_ib: Use v2 version of cfg_rx_steer_req to enable RX coalescing (bsc#1239016).
• Revert 'gfs2: Fix inode height consistency check (git-fixes).
• btrfs: defrag: do not use merged extent map for their generation check (bsc#1239968).
• btrfs: fix defrag not merging contiguous extents due to merged extent maps (bsc#1239968).
• btrfs: fix extent map merging not happening for adjacent extents (bsc#1239968).
• btrfs: send: allow cloning non-aligned extent if it ends at i_size (bsc#1239969).
• btrfs: send: fix invalid clone operation for file that got its size decreased (bsc#1239969).
• cifs: Add a laundromat thread for cached directories (git-fixes).
• cifs: fix potential null pointer use in destroy_workqueue in init_cifs error path (git-fixes).
• gfs2: Fix inode height consistency check (git-fixes).
• mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() (bsc#1239126).
• mm: zswap: move allocations during CPU init outside the lock (git-fixes).
• net: mana: Add flex array to struct mana_cfg_rx_steer_req_v2 (bsc#1239016).
• net: mana: Allow variable size indirection table (bsc#1239016).
• net: mana: Avoid open coded arithmetic (bsc#1239016).
• net: mana: Support holes in device list reply msg (bsc#1240133).
• sched/membarrier: Fix redundant load of membarrier_state (bsc#1232743).
• smb3: allow controlling length of time directory entries are cached with dir leases (git-fixes).
• smb3: do not start laundromat thread when dir leases disabled (git-fixes).
• smb3: retrying on failed server close (git-fixes).
• smb: client: destroy cfid_put_wq on module exit (git-fixes).
• smb: client: disable directory caching when dir_cache_timeout is zero (git-fixes).
• smb: client: do not start laundromat thread on nohandlecache (git-fixes).
• smb: client: make laundromat a delayed worker (git-fixes).
• smb: client: properly close cfids on umount (bsc#1231432, bsc#1232299, bsc#1235599, bsc#1234896).
• tpm: send_data: Wait longer for the TPM to become ready (bsc#1235870).

The SUSE Linux Enterprise 15 SP4 RT kernel was updated to receive various security bugfixes.

The following security bugs were fixed:

• CVE-2022-49053: scsi: target: tcmu: Fix possible page UAF (bsc#1237918).
• CVE-2022-49465: blk-throttle: Set BIO_THROTTLED when bio has been throttled (bsc#1238919).
• CVE-2022-49739: gfs2: Always check inode size of inline inodes (bsc#1240207).
• CVE-2023-52935: mm/khugepaged: fix ->anon_vma race (bsc#1240276).
• CVE-2024-2201: Fixed information leak in x86/BHI (bsc#1217339).
• CVE-2024-41092: drm/i915/gt: Fix potential UAF by revoke of fence registers (bsc#1228483).
• CVE-2024-42098: crypto: ecdh - explicitly zeroize private_key (bsc#1228779).
• CVE-2024-42229: crypto: aead,cipher - zeroize key buffer after use (bsc#1228708).
• CVE-2024-53064: idpf: fix idpf_vc_core_init error path (bsc#1233558 bsc#1234464).
• CVE-2024-56651: can: hi311x: hi3110_can_ist(): fix potential use-after-free (bsc#1235528).
• CVE-2024-57996: net_sched: sch_sfq: do not allow 1 packet limit (bsc#1239076).
• CVE-2024-58014: wifi: brcmsmac: add gain range check to wlc_phy_iqcal_gainparams_nphy() (bsc#1239109).
• CVE-2024-58083: KVM: Explicitly verify target vCPU is online in kvm_get_vcpu() (bsc#1239036).
• CVE-2025-21693: mm: zswap: properly synchronize freeing resources during CPU hotunplug (bsc#1237029).
• CVE-2025-21714: RDMA/mlx5: Fix implicit ODP use after free (bsc#1237890).
• CVE-2025-21718: net: rose: fix timer races against user threads (bsc#1239073).
• CVE-2025-21732: RDMA/mlx5: Fix a race for an ODP MR which leads to CQE with error (bsc#1237877).
• CVE-2025-21753: btrfs: fix use-after-free when attempting to join an aborted transaction (bsc#1237875).
• CVE-2025-21772: partitions: mac: fix handling of bogus partition table (bsc#1238911).
• CVE-2025-21780: drm/amdgpu: avoid buffer overflow attach in smu_sys_set_pp_table() (bsc#1239115).
• CVE-2025-21839: kABI: Fix kABI after backport od CVE-2025-21839 (bsc#1239061).

The following non-security bugs were fixed:

• ACPI: processor: idle: Return an error if both P_LVL{2,3} idle states are invalid (bsc#1237530).
• RDMA/mana_ib: Prefer struct_size over open coded arithmetic (bsc#1239016).
• RDMA/mana_ib: Use v2 version of cfg_rx_steer_req to enable RX coalescing (bsc#1239016).
• RDMA/mlx5: Fix implicit ODP hang on parent deregistration (git-fixes)
• btrfs: defrag: do not use merged extent map for their generation check (bsc#1239968).
• btrfs: fix defrag not merging contiguous extents due to merged extent maps (bsc#1239968).
• btrfs: fix extent map merging not happening for adjacent extents (bsc#1239968).
• btrfs: send: allow cloning non-aligned extent if it ends at i_size (bsc#1239969).
• btrfs: send: fix invalid clone operation for file that got its size decreased (bsc#1239969).
• gfs2: Fix inode height consistency check (git-fixes).
• mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() (bsc#1239126).
• mm: zswap: move allocations during CPU init outside the lock (git-fixes).
• net: mana: Add flex array to struct mana_cfg_rx_steer_req_v2 (bsc#1239016).
• net: mana: Allow variable size indirection table (bsc#1239016).
• net: mana: Avoid open coded arithmetic (bsc#1239016).
• net: mana: Fix error handling in mana_create_txq/rxq's NAPI cleanup (bsc#1240195).
• net: mana: Support holes in device list reply msg (bsc#1240133).
• x86/bhi: Avoid warning in #DB handler due to BHI mitigation (git-fixes).
• x86/bugs: Cache the value of MSR_IA32_ARCH_CAPABILITIES (git-fixes).
• x86/bugs: Fix BHI documentation (git-fixes).
• x86/bugs: Fix BHI handling of RRSBA (git-fixes).
• x86/bugs: Fix BHI retpoline check (git-fixes).
• x86/bugs: Fix return type of spectre_bhi_state() (git-fixes).
• x86/bugs: Remove CONFIG_BHI_MITIGATION_AUTO and spectre_bhi=auto (git-fixes).

The SUSE Linux Enterprise 15 SP5 kernel was updated to receive various security bugfixes.

The following security bugs were fixed:

• CVE-2022-49053: scsi: target: tcmu: Fix possible page UAF (bsc#1237918).
• CVE-2022-49465: blk-throttle: Set BIO_THROTTLED when bio has been throttled (bsc#1238919).
• CVE-2022-49739: gfs2: Always check inode size of inline inodes (bsc#1240207).
• CVE-2023-52935: mm/khugepaged: fix ->anon_vma race (bsc#1240276).
• CVE-2024-53124: net: fix data-races around sk->sk_forward_alloc (bsc#1234074).
• CVE-2024-53176: smb: During unmount, ensure all cached dir instances drop their dentry (bsc#1234894).
• CVE-2024-53178: smb: Do not leak cfid when reconnect races with open_cached_dir (bsc#1234895).
• CVE-2024-56651: can: hi311x: hi3110_can_ist(): fix potential use-after-free (bsc#1235528).
• CVE-2024-57996: net_sched: sch_sfq: do not allow 1 packet limit (bsc#1239076).
• CVE-2024-58013: Bluetooth: MGMT: Fix slab-use-after-free Read in mgmt_remove_adv_monitor_sync (bsc#1239095).
• CVE-2024-58014: wifi: brcmsmac: add gain range check to wlc_phy_iqcal_gainparams_nphy() (bsc#1239109).
• CVE-2025-21693: mm: zswap: properly synchronize freeing resources during CPU hotunplug (bsc#1237029).
• CVE-2025-21718: net: rose: fix timer races against user threads (bsc#1239073).
• CVE-2025-21772: partitions: mac: fix handling of bogus partition table (bsc#1238911).
• CVE-2025-21780: drm/amdgpu: avoid buffer overflow attach in smu_sys_set_pp_table() (bsc#1239115).

The following non-security bugs were fixed:

• ACPI: processor: idle: Return an error if both P_LVL{2,3} idle states are invalid (bsc#1237530).
• btrfs: defrag: do not use merged extent map for their generation check (bsc#1239968).
• btrfs: fix defrag not merging contiguous extents due to merged extent maps (bsc#1239968).
• btrfs: fix extent map merging not happening for adjacent extents (bsc#1239968).
• btrfs: send: allow cloning non-aligned extent if it ends at i_size (bsc#1239969).
• btrfs: send: fix invalid clone operation for file that got its size decreased (bsc#1239969).
• cifs: Add a laundromat thread for cached directories (git-fixes).
• cifs: fix potential null pointer use in destroy_workqueue in init_cifs error path (git-fixes).
• gfs2: Fix inode height consistency check (git-fixes).
• mm: zswap: move allocations during CPU init outside the lock (git-fixes).
• mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() (bsc#1239126).
• net: mana: Add flex array to struct mana_cfg_rx_steer_req_v2 (bsc#1239016).
• net: mana: Allow variable size indirection table (bsc#1239016).
• net: mana: Avoid open coded arithmetic (bsc#1239016).
• net: mana: Support holes in device list reply msg (bsc#1240133).
• RDMA/mana_ib: Prefer struct_size over open coded arithmetic (bsc#1239016).
• RDMA/mana_ib: Use v2 version of cfg_rx_steer_req to enable RX coalescing (bsc#1239016).
• sched/membarrier: Fix redundant load of membarrier_state (bsc#1232743).
• smb: client: destroy cfid_put_wq on module exit (git-fixes).
• smb: client: disable directory caching when dir_cache_timeout is zero (git-fixes).
• smb: client: do not start laundromat thread on nohandlecache (git-fixes).
• smb: client: make laundromat a delayed worker (git-fixes).
• smb: client: properly close cfids on umount (bsc#1231432, bsc#1232299, bsc#1235599, bsc#1234896).
• smb3: allow controlling length of time directory entries are cached with dir leases (git-fixes).
• smb3: do not start laundromat thread when dir leases disabled (git-fixes).
• smb3: retrying on failed server close (git-fixes).
• tpm: send_data: Wait longer for the TPM to become ready (bsc#1235870).