linux-kernel - [PATCH v2] mm: kmsan: Panic on failure to allocate early boot metadata

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Message-ID: <20231016153446.132763-1-pedro.falcato@gmail.com>
Date:   Mon, 16 Oct 2023 16:34:46 +0100
From:   Pedro Falcato <pedro.falcato@...il.com>
To:     kasan-dev@...glegroups.com, Alexander Potapenko <glider@...gle.com>
Cc:     Marco Elver <elver@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Pedro Falcato <pedro.falcato@...il.com>
Subject: [PATCH v2] 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.

Signed-off-by: Pedro Falcato <pedro.falcato@...il.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(-)

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;
 	}
-- 
2.42.0