Subject: CVE-2024-26712: powerpc/kasan: Fix addr error caused by page alignment

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

powerpc/kasan: Fix addr error caused by page alignment

In kasan_init_region, when k_start is not page aligned, at the begin of
for loop, k_cur = k_start & PAGE_MASK is less than k_start, and then
`va = block + k_cur - k_start` is less than block, the addr va is invalid,
because the memory address space from va to block is not alloced by
memblock_alloc, which will not be reserved by memblock_reserve later, it
will be used by other places.

As a result, memory overwriting occurs.

for example:
int __init __weak kasan_init_region(void *start, size_t size)
{
[...]
	/* if say block(dcd97000) k_start(feef7400) k_end(feeff3fe) */
	block = memblock_alloc(k_end - k_start, PAGE_SIZE);
	[...]
	for (k_cur = k_start & PAGE_MASK; k_cur < k_end; k_cur += PAGE_SIZE) {
		/* at the begin of for loop
		 * block(dcd97000) va(dcd96c00) k_cur(feef7000) k_start(feef7400)
		 * va(dcd96c00) is less than block(dcd97000), va is invalid
		 */
		void *va = block + k_cur - k_start;
		[...]
	}
[...]
}

Therefore, page alignment is performed on k_start before
memblock_alloc() to ensure the validity of the VA address.

The Linux kernel CVE team has assigned CVE-2024-26712 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.4 with commit 663c0c9496a6 and fixed in 5.10.210 with commit 230e89b5ad0a
	Issue introduced in 5.4 with commit 663c0c9496a6 and fixed in 5.15.149 with commit 2738e0aa2fb2
	Issue introduced in 5.4 with commit 663c0c9496a6 and fixed in 6.1.79 with commit 0c09912dd838
	Issue introduced in 5.4 with commit 663c0c9496a6 and fixed in 6.6.18 with commit 0516c06b19dc
	Issue introduced in 5.4 with commit 663c0c9496a6 and fixed in 6.7.6 with commit 70ef2ba1f428
	Issue introduced in 5.4 with commit 663c0c9496a6 and fixed in 6.8 with commit 4a7aee96200a
	Issue introduced in 5.3.6 with commit 5ce93076d8ee

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26712
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	arch/powerpc/mm/kasan/init_32.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/230e89b5ad0a33f530a2a976b3e5e4385cb27882
	https://git.kernel.org/stable/c/2738e0aa2fb24a7ab9c878d912dc2b239738c6c6
	https://git.kernel.org/stable/c/0c09912dd8387e228afcc5e34ac5d79b1e3a1058
	https://git.kernel.org/stable/c/0516c06b19dc64807c10e01bb99b552bdf2d7dbe
	https://git.kernel.org/stable/c/70ef2ba1f4286b2b73675aeb424b590c92d57b25
	https://git.kernel.org/stable/c/4a7aee96200ad281a5cc4cf5c7a2e2a49d2b97b0