x86/mm: Check return value from memblock_phys_alloc_range()

Overview

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

x86/mm: Check return value from memblock_phys_alloc_range()

At least with CONFIG_PHYSICAL_START=0x100000, if there is < 4 MiB of contiguous free memory available at this point, the kernel will crash and burn because memblock_phys_alloc_range() returns 0 on failure, which leads memblock_phys_free() to throw the first 4 MiB of physical memory to the wolves.

At a minimum it should fail gracefully with a meaningful diagnostic, but in fact everything seems to work fine without the weird reserve allocation.

Affected

• Linux >= a7259df7670240ee03b0cfce8a3e5d3773911e24 < 8c18c904d301ffeb33b071eadc55cd6131e1e9be
• Linux >= a7259df7670240ee03b0cfce8a3e5d3773911e24 < bffd5f2815c5234d609725cd0dc2f4bc5de2fc67
• Linux >= a7259df7670240ee03b0cfce8a3e5d3773911e24 < c6f2694c580c27dca0cf7546ee9b4bfa6b940e38
• Linux >= a7259df7670240ee03b0cfce8a3e5d3773911e24 < dde4800d2b0f68b945fd81d4fc2d4a10ae25f743
• Linux >= a7259df7670240ee03b0cfce8a3e5d3773911e24 < 631ca8909fd5c62b9fda9edda93924311a78a9c4
• Linux 5.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.