6.1-stable review patch. If anyone has any objections, please let me know.
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From: Jiangfeng Xiao xiaojiangfeng@huawei.com
[ Upstream commit 4a7aee96200ad281a5cc4cf5c7a2e2a49d2b97b0 ]
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.co... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/mm/kasan/init_32.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/mm/kasan/init_32.c b/arch/powerpc/mm/kasan/init_32.c index a70828a6d935..aa9aa11927b2 100644 --- a/arch/powerpc/mm/kasan/init_32.c +++ b/arch/powerpc/mm/kasan/init_32.c @@ -64,6 +64,7 @@ int __init __weak kasan_init_region(void *start, size_t size) if (ret) return ret;
+ k_start = k_start & PAGE_MASK; block = memblock_alloc(k_end - k_start, PAGE_SIZE); if (!block) return -ENOMEM;