x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

From: Mike Galbraith
Date: Thu Apr 15 2021 - 13:56:30 EST


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@xxxxxx>
---
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;