of: check previous kernel's ima-kexec-buffer against memory bounds
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 PFN range of previous kernel's
ima-kexec-buffer with page_is_ram() to ensure correct memory bounds.
Fixes:
467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel")
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Prakhar Srivastava <prsriva@linux.microsoft.com>
Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Ritesh Harjani <ritesh.list@gmail.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220531041446.3334259-1-vaibhav@linux.ibm.com