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powerpc Fix addr error caused by page alignment

Mamatha Inamdar requested to merge mainamdar/centos-stream-9:RHEL-33707 into main

Description: powerpc Fix addr error caused by page alignment

JIRA: https://issues.redhat.com/browse/RHEL-33707

CVE: CVE-2024-26712

Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=60816408

Tested: Verified Brew build test kernel RPMs

Signed-off-by: Mamatha Inamdar minamdar@redhat.com

commit 4a7aee96200ad281a5cc4cf5c7a2e2a49d2b97b0 Author: Jiangfeng Xiao xiaojiangfeng@huawei.com Date: Tue Jan 23 09:45:59 2024 +0800

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.

Fixes: 663c0c9496a6 ("powerpc/kasan: Fix shadow area set up for modules.")
Signed-off-by: Jiangfeng Xiao <xiaojiangfeng@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/1705974359-43790-1-git-send-email-xiaojiangfeng@huawei.com

Signed-off-by: Mamatha Inamdar minamdar@redhat.com

Edited by Mamatha Inamdar

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