| Message ID | 20231016153446.132763-1-pedro.falcato@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] mm: kmsan: Panic on failure to allocate early boot metadata | expand |
On Mon, Oct 16, 2023 at 5:34 PM Pedro Falcato <pedro.falcato@gmail.com> wrote: > > Given large enough allocations and a machine with low enough memory (i.e > a default QEMU VM), it's entirely possible that > kmsan_init_alloc_meta_for_range's shadow+origin allocation fails. > > Instead of eating a NULL deref kernel oops, check explicitly for > memblock_alloc() failure and panic with a nice error message. For posterity, it is generally quite important for the allocated shadow and origin to be contiguous, otherwise an unaligned memory write may result in memory corruption (the corresponding unaligned shadow write will be assuming that shadow pages are adjacent). So instead of panicking we could have split the range into smaller ones until the allocation succeeds, but that would've led to hard-to-debug problems in the future. > > Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com> Reviewed-by: Alexander Potapenko <glider@google.com>
diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c index 87318f9170f..b9d05aff313 100644 --- a/mm/kmsan/shadow.c +++ b/mm/kmsan/shadow.c @@ -285,12 +285,17 @@ void __init kmsan_init_alloc_meta_for_range(void *start, void *end) size = PAGE_ALIGN((u64)end - (u64)start); shadow = memblock_alloc(size, PAGE_SIZE); origin = memblock_alloc(size, PAGE_SIZE); + + if (!shadow || !origin) + panic("%s: Failed to allocate metadata memory for early boot range of size %llu", + __func__, size); + for (u64 addr = 0; addr < size; addr += PAGE_SIZE) { page = virt_to_page_or_null((char *)start + addr); - shadow_p = virt_to_page_or_null((char *)shadow + addr); + shadow_p = virt_to_page((char *)shadow + addr); set_no_shadow_origin_page(shadow_p); shadow_page_for(page) = shadow_p; - origin_p = virt_to_page_or_null((char *)origin + addr); + origin_p = virt_to_page((char *)origin + addr); set_no_shadow_origin_page(origin_p); origin_page_for(page) = origin_p; }
Given large enough allocations and a machine with low enough memory (i.e a default QEMU VM), it's entirely possible that kmsan_init_alloc_meta_for_range's shadow+origin allocation fails. Instead of eating a NULL deref kernel oops, check explicitly for memblock_alloc() failure and panic with a nice error message. Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com> --- v2: Address checkpatch warnings, namely: - Unsplit a user-visible string - Split an overly long line in the commit message mm/kmsan/shadow.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)