linux-kernel - x86/crash: fix crash_setup_memmap

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Date:   Thu, 15 Apr 2021 19:56:21 +0200
From:   Mike Galbraith <efault@....de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>
Subject: x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

x86/crash: fix crash_setup_memmap_entries() KASAN vmalloc-out-of-bounds gripe

[   15.428011] BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
[   15.428018] Write of size 8 at addr ffffc90000426008 by task kexec/1187

(gdb) list *crash_setup_memmap_entries+0x17e
0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
317                                      unsigned long long mend)
318     {
319             unsigned long start, end;
320
321             cmem->ranges[0].start = mstart;
322             cmem->ranges[0].end = mend;
323             cmem->nr_ranges = 1;
324
325             /* Exclude elf header region */
326             start = image->arch.elf_load_addr;
(gdb)

We're excluding two ranges, allocate the scratch space we need to do that.

Signed-off-by: Mike Galbraith <efault@....de>
---
 arch/x86/kernel/crash.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct ki
 	struct crash_memmap_data cmd;
 	struct crash_mem *cmem;

-	cmem = vzalloc(sizeof(struct crash_mem));
+	cmem = vzalloc(sizeof(struct crash_mem)+(2*sizeof(struct crash_mem_range)));
 	if (!cmem)
 		return -ENOMEM;