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

ubifs: rename_whiteout: Fix double free for whiteout_ui->data

'whiteout_ui->data' will be freed twice if space budget fail for
rename whiteout operation as following process:

rename_whiteout
dev = kmalloc
whiteout_ui->data = dev
kfree(whiteout_ui->data) // Free first time
iput(whiteout)
ubifs_free_inode
kfree(ui->data) // Double free!

KASAN reports:

BUG: KASAN: double-free or invalid-free in ubifs_free_inode+0x4f/0x70
Call Trace:
kfree+0x117/0x490
ubifs_free_inode+0x4f/0x70 [ubifs]
i_callback+0x30/0x60
rcu_do_batch+0x366/0xac0
__do_softirq+0x133/0x57f

Allocated by task 1506:
kmem_cache_alloc_trace+0x3c2/0x7a0
do_rename+0x9b7/0x1150 [ubifs]
ubifs_rename+0x106/0x1f0 [ubifs]
do_syscall_64+0x35/0x80

Freed by task 1506:
kfree+0x117/0x490
do_rename.cold+0x53/0x8a [ubifs]
ubifs_rename+0x106/0x1f0 [ubifs]
do_syscall_64+0x35/0x80

The buggy address belongs to the object at ffff88810238bed8 which
belongs to the cache kmalloc-8 of size 8

Let ubifs_free_inode() free 'whiteout_ui->data'. BTW, delete unused
assignment 'whiteout_ui->data_len = 0', process 'ubifs_evict_inode()
-> ubifs_jnl_delete_inode() -> ubifs_jnl_write_inode()' doesn't need it
(because 'inc_nlink(whiteout)' won't be excuted by 'goto out_release',
and the nlink of whiteout inode is 0).

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-47638
• https://git.kernel.org/stable/c/14276d38c89a170363e90b6ac0a53c3cf61b87fc
• https://git.kernel.org/stable/c/2ad07009c459e56ebdcc089d850d664660fdb742
• https://git.kernel.org/stable/c/2b3236ecf96db7af5836e1366ce39ace8ce832fa
• https://git.kernel.org/stable/c/40a8f0d5e7b3999f096570edab71c345da812e3e
• https://git.kernel.org/stable/c/6d7a158a7363c1f6604aa47ae1a280a5c65123dd
• https://git.kernel.org/stable/c/8b3c7be16f3f4dfd6e15ac651484e59d3fa36274
• https://git.kernel.org/stable/c/a90e2dbe66d2647ff95a0442ad2e86482d977fd8
• https://git.kernel.org/stable/c/b9a937f096e608b3368c1abc920d4d640ba2c94f