[SRU][M/F][PATCH 0/1] CVE-2024-26712

[Bethany Jamison]

[Impact]

 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.

[Fix]

Mantic: Clean cherry-pick from linux-6.6.y
Jammy:	pending
Focal:	Backport - manually added the k_start realignment right before 
	memblock_alloc despite the context conflicts with the surrounding 
	code.
Bionic:	not-affected
Xenial:	not-affected
Trusty:	not-affected

[Test Case]

Compile and boot tested.

[Where problems could occur]

This fix affects those who use KASAN on PowerPC when initializing a 
memory region, an issue with this fix would be visable to the user via
data corruption or a system crash.

Jiangfeng Xiao (1):
  powerpc/kasan: Fix addr error caused by page alignment

 arch/powerpc/mm/kasan/init_32.c | 1 +
 1 file changed, 1 insertion(+)

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2.34.1