On 04/19/21 at 10:52am, Borislav Petkov wrote:
> Here's an attempt to explain what this fixes:
>
> ---
> From: Mike Galbraith <efault@xxxxxx>
> Date: Fri, 16 Apr 2021 14:02:07 +0200
> Subject: [PATCH] x86/crash: Fix crash_setup_memmap_entries() out-of-bounds
> access
>
> Commit in Fixes: added support for kexec-ing a kernel on panic using a
> new system call. As part of it, it does prepare a memory map for the new
> kernel.
>
> However, while doing so, it wrongly accesses memory it has not
> allocated: it accesses the first element of the cmem->ranges[] array in
> memmap_exclude_ranges() but it has not allocated the memory for it in
> crash_setup_memmap_entries(). As KASAN reports:
>
> BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
> 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)
>
> Make sure the ranges array becomes a single element allocated.
>
> [ bp: Write a proper commit message. ]
Reviewed-by: Dave Young <dyoung@xxxxxxxxxx>
>
> Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
> Signed-off-by: Mike Galbraith <efault@xxxxxx>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> Link: https://lkml.kernel.org/r/725fa3dc1da2737f0f6188a1a9701bead257ea9d.camel@xxxxxx
> ---
> arch/x86/kernel/crash.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index a8f3af257e26..b1deacbeb266 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
> struct crash_memmap_data cmd;
> struct crash_mem *cmem;
>
> - cmem = vzalloc(sizeof(struct crash_mem));
> + cmem = vzalloc(struct_size(cmem, ranges, 1));
> if (!cmem)
> return -ENOMEM;
>
> --
> 2.29.2
>
> --
> Regards/Gruss,
> Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette
>
Thanks
Dave
_______________________________________________
kexec mailing list
kexec@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/kexec
