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.

Weakness

The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/1cead23c1c0bc766dacb900a3b0269f651ad596f
• https://git.kernel.org/stable/c/36e911a16b377bde0ad91a8c679069d0d310b1a6
• https://git.kernel.org/stable/c/3dae1a4eced3ee733d7222e69b8a55caf2d61091
• https://git.kernel.org/stable/c/50cc1462a668dc62949a1127388bc3af785ce047
• https://git.kernel.org/stable/c/55e6d8037805b3400096d621091dfbf713f97e83
• https://git.kernel.org/stable/c/758ced2c3878ff789801e6fee808e185c5cf08d6
• https://git.kernel.org/stable/c/e72dce9afbdbfa70d9b44f5908a50ff6c4858999
• https://git.kernel.org/stable/c/fc081477b47dfc3a6cb50a96087fc29674013fc2
• https://git.kernel.org/stable/c/1cead23c1c0bc766dacb900a3b0269f651ad596f
• https://git.kernel.org/stable/c/36e911a16b377bde0ad91a8c679069d0d310b1a6
• https://git.kernel.org/stable/c/3dae1a4eced3ee733d7222e69b8a55caf2d61091
• https://git.kernel.org/stable/c/50cc1462a668dc62949a1127388bc3af785ce047
• https://git.kernel.org/stable/c/55e6d8037805b3400096d621091dfbf713f97e83
• https://git.kernel.org/stable/c/758ced2c3878ff789801e6fee808e185c5cf08d6
• https://git.kernel.org/stable/c/e72dce9afbdbfa70d9b44f5908a50ff6c4858999
• https://git.kernel.org/stable/c/fc081477b47dfc3a6cb50a96087fc29674013fc2