Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> writes:
>
> [PATCH] powerpc: check previous kernel's ima-kexec-buffer against memory bounds
This isn't a powerpc patch, the subject should start with "of:".
> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
> ima-kexec-buffer lies outside the addressable memory range. This can result
> in a kernel panic if the new kernel is booted with 'mem=X' arg and the
> ima-kexec-buffer was allocated beyond that range by the previous kernel.
> The panic is usually of the form below:
>
> $ sudo kexec --initrd initrd vmlinux --append='mem=16G'
>
> <snip>
> BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000
> Faulting instruction address: 0xc000000000837974
> Oops: Kernel access of bad area, sig: 11 [#1]
> <snip>
> NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0
> LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
> Call Trace:
> [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
> [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108
> [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120
> [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0
> [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec
> [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0
> [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64
> Instruction dump:
> f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330
> 7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010
> ---[ end trace 0000000000000000 ]---
>
> Fix this issue by checking returned address/size of previous kernel's
> ima-kexec-buffer against memblock's memory bounds.
>
> Fixes: fee3ff99bc67("powerpc: Move arch independent ima kexec functions to
> drivers/of/kexec.c")
>
> Cc: Frank Rowand <frowand.list@xxxxxxxxx>
> Cc: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> Cc: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
> Cc: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
> Cc: Rob Herring <robh@xxxxxxxxxx>
> Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
> ---
> drivers/of/kexec.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index b9bd1cff1793..c73007eda52d 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -140,6 +140,13 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
> if (ret)
> return ret;
>
> + /* if the ima-kexec-buffer goes beyond the addressable memory */
> + if (!memblock_is_region_memory(tmp_addr, tmp_size)) {
Not all arches keep the memblock info around after boot.
I think this will be called too late, but I'd have to check the exact
timing to be sure.
I think you can use pfn_valid() instead?
cheers
> + pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
> + tmp_addr, tmp_size);
> + return -EINVAL;
> + }
> +
> *addr = __va(tmp_addr);
> *size = tmp_size;
>
> --
> 2.35.1
