| Message ID | 20240422170742.19770-3-bethany.jamison@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [SRU,F,1/1] powerpc/kasan: Fix addr error caused by page alignment | expand |
On 4/22/24 12:07 PM, Bethany Jamison wrote: > From: Jiangfeng Xiao <xiaojiangfeng@huawei.com> > > 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 > (backported from commit 4a7aee96200ad281a5cc4cf5c7a2e2a49d2b97b0) > [bjamison: context conflict - added k_start realignment to appropriate spot in code] > CVE-2024-26712 > Signed-off-by: Bethany Jamison <bethany.jamison@canonical.com> > --- > arch/powerpc/mm/kasan/kasan_init_32.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c > index 3f78007a72822..8a294f94a7ca3 100644 > --- a/arch/powerpc/mm/kasan/kasan_init_32.c > +++ b/arch/powerpc/mm/kasan/kasan_init_32.c > @@ -91,6 +91,7 @@ static int __ref kasan_init_region(void *start, size_t size) > return ret; > > if (!slab_is_available()) > + k_start = k_start & PAGE_MASK; > block = memblock_alloc(k_end - k_start, PAGE_SIZE); Curly braces are needed for the above `if` block, since a 2nd line is being added to it. Jacob > > for (k_cur = k_start & PAGE_MASK; k_cur < k_end; k_cur += PAGE_SIZE) {
diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c index 3f78007a72822..8a294f94a7ca3 100644 --- a/arch/powerpc/mm/kasan/kasan_init_32.c +++ b/arch/powerpc/mm/kasan/kasan_init_32.c @@ -91,6 +91,7 @@ static int __ref kasan_init_region(void *start, size_t size) return ret; if (!slab_is_available()) + k_start = k_start & PAGE_MASK; block = memblock_alloc(k_end - k_start, PAGE_SIZE); for (k_cur = k_start & PAGE_MASK; k_cur < k_end; k_cur += PAGE_SIZE) {