From 09aec5f9b2505c73a9380800f61ad920cc64a7cd Mon Sep 17 00:00:00 2001 From: Pedro Falcato Date: Mon, 16 Oct 2023 16:34:46 +0100 Subject: [PATCH] mm: kmsan: panic on failure to allocate early boot metadata 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. Alexander Potapenko said: 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. Link: https://lkml.kernel.org/r/20231016153446.132763-1-pedro.falcato@gmail.com Signed-off-by: Pedro Falcato Reviewed-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: Marco Elver Signed-off-by: Andrew Morton --- mm/kmsan/shadow.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c index 87318f9170f1..b9d05aff313e 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; }