CVE-2022-49152 Information

Description

In the Linux kernel the following vulnerability has been resolved:

XArray: Fix xas_create_range() when multi-order entry present

If there is already an entry present that is of order >= XA_CHUNK_SHIFT when we call xas_create_range() xas_create_range() will misinterpret that entry as a node and dereference xa_node->parent generally leading to a crash that looks something like this:

general protection fault probably for non-canonical address 0xdffffc0000000001: 0000 [1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 0 PID: 32 Comm: khugepaged Not tainted 5.17.0-rc8-syzkaller-00003-g56e337f2cf13 0 RIP: 0010:xa_parent_locked include/linux/xarray.h:1207 [inline] RIP: 0010:xas_create_range+0x2d9/0x6e0 lib/xarray.c:725

It’s deterministically reproducable once you know what the problem is but producing it in a live kernel requires khugepaged to hit a race. While the problem has been present since xas_create_range() was introduced I’m not aware of a way to hit it before the page cache was converted to use multi-index entries.

Reference

https://git.kernel.org/stable/c/18f13edf3424b3b61814b69d5269b2e14584800c https://git.kernel.org/stable/c/1ac49c8fd49fdf53d3cd8b77eb8ffda08d7fbe22 https://git.kernel.org/stable/c/29968329b926d238e3107ec071a250397555d264 https://git.kernel.org/stable/c/3e2852eda19ee1a400cd809d7a9322680f34a262 https://git.kernel.org/stable/c/3e3c658055c002900982513e289398a1aad4a488 https://git.kernel.org/stable/c/7521a97b1929042604bef6859f62fa8b4bbc077b