CVE-2021-47483

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

regmap: Fix possible double-free in regcache_rbtree_exit()

In regcache_rbtree_insert_to_block(), when 'present' realloc failed,

the 'blk' which is supposed to assign to 'rbnode->block' will be freed,

so 'rbnode->block' points a freed memory, in the error handling path of

regcache_rbtree_init(), 'rbnode->block' will be freed again in

regcache_rbtree_exit(), KASAN will report double-free as follows:

BUG: KASAN: double-free or invalid-free in kfree+0xce/0x390

Call Trace:

slab_free_freelist_hook+0x10d/0x240

kfree+0xce/0x390

regcache_rbtree_exit+0x15d/0x1a0

regcache_rbtree_init+0x224/0x2c0

regcache_init+0x88d/0x1310

__regmap_init+0x3151/0x4a80

__devm_regmap_init+0x7d/0x100

madera_spi_probe+0x10f/0x333 [madera_spi]

spi_probe+0x183/0x210

really_probe+0x285/0xc30

To fix this, moving up the assignment of rbnode->block to immediately after

the reallocation has succeeded so that the data structure stays valid even

if the second reallocation fails.