CVE-2022-49152

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

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

If there is already an entry present that is of order >= XACHUNKSHIFT when we call xascreaterange(), xascreaterange() 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:xaparentlocked include/linux/xarray.h:1207 [inline] RIP: 0010:xascreaterange+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 xascreaterange() was introduced, I'm not aware of a way to hit it before the page cache was converted to use multi-index entries.