[PATCH] Update creation of flash_block_cache to accout for potential panic
From: Audra Mitchell
Date: Mon Aug 28 2023 - 16:56:50 EST
With PPC builds enabling CONFIG_HARDENED_USERCOPY, interacting with the RunTime
Abstraction Services (RTAS) firmware by writing to
/proc/powerpc/rtas/firmware_flash will end up triggering the mm/usercopy.c:101
assertion:
[ 38.647148] rw /proc/powerpc/rtas/firmware_flash
[ 38.650254] usercopy: Kernel memory overwrite attempt detected to SLUB object 'rtas_flash_cache' (offset 0, size 34)!
[ 38.650264] ------------[ cut here ]------------
[ 38.650264] kernel BUG at mm/usercopy.c:101!
[ 38.650267] Oops: Exception in kernel mode, sig: 5 [#1]
[ 38.650283] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
[ 38.650287] Modules linked in: binfmt_misc loop rfkill bonding tls sunrpc pseries_rng drm fuse drm_panel_orientation_quirks xfs libcrc32c sd_mod t10_pi sg ibmveth ibmvscsi scsi_transport_srp vmx_crypto
[ 38.650306] CPU: 0 PID: 12898 Comm: echo Kdump: loaded Not tainted 5.14.0-299.el9.ppc64le #1
[ 38.650311] NIP: c00000000056d870 LR: c00000000056d86c CTR: c000000000886090
[ 38.650314] REGS: c0000000ba6e78c0 TRAP: 0700 Not tainted (5.14.0-299.el9.ppc64le)
[ 38.650318] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 28002203 XER: 20040000
[ 38.650326] CFAR: c0000000001f76fc IRQMASK: 0
[ 38.650326] GPR00: c00000000056d86c c0000000ba6e7b60 c000000002b15a00 0000000000000069
[ 38.650326] GPR04: c000000fff447f90 c000000fff4ccd00 000000000000000f 0000000000000027
[ 38.650326] GPR08: 0000000000000000 c000000fff44adc0 0000000ffd2f0000 0000000000002000
[ 38.650326] GPR12: 6174722720746365 c000000002ea0000 0000000000000000 0000000000000000
[ 38.650326] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 38.650326] GPR20: 0000000000000000 0000000000000000 0000000000000002 0000000000000001
[ 38.650326] GPR24: 0000000000000000 000000012eef55a0 c0000000025f39e0 c0000000b988d000
[ 38.650326] GPR28: c0000000b988d022 0000000000000022 0000000000000000 c00000000134d6e8
[ 38.650366] NIP [c00000000056d870] usercopy_abort+0xb0/0xc0
[ 38.650373] LR [c00000000056d86c] usercopy_abort+0xac/0xc0
[ 38.650377] Call Trace:
[ 38.650379] [c0000000ba6e7b60] [c00000000056d86c] usercopy_abort+0xac/0xc0 (unreliable)
[ 38.650384] [c0000000ba6e7be0] [c0000000005178f0] __check_heap_object+0xf0/0x120
[ 38.650389] [c0000000ba6e7c00] [c00000000056d5e0] check_heap_object+0x1f0/0x220
[ 38.650394] [c0000000ba6e7c40] [c00000000056d6a0] __check_object_size+0x90/0x1b0
[ 38.650399] [c0000000ba6e7c80] [c0000000000462fc] rtas_flash_write+0x11c/0x2b0
[ 38.650404] [c0000000ba6e7ce0] [c00000000064d2ec] proc_reg_write+0xfc/0x160
[ 38.650409] [c0000000ba6e7d10] [c000000000579e64] vfs_write+0xe4/0x390
[ 38.650413] [c0000000ba6e7d60] [c00000000057a414] ksys_write+0x84/0x140
[ 38.650417] [c0000000ba6e7db0] [c00000000002f314] system_call_exception+0x164/0x310
[ 38.650421] [c0000000ba6e7e10] [c00000000000bfe8] system_call_vectored_common+0xe8/0x278
[ 38.650426] --- interrupt: 3000 at 0x7fff87f3aa34
[ 38.650430] NIP: 00007fff87f3aa34 LR: 0000000000000000 CTR: 0000000000000000
[ 38.650433] REGS: c0000000ba6e7e80 TRAP: 3000 Not tainted (5.14.0-299.el9.ppc64le)
[ 38.650436] MSR: 800000000280f033 <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 42002408 XER: 00000000
[ 38.650446] IRQMASK: 0
This used to be caught with a warning in __check_heap_object to allow impacted
drivers time to update to kmem_cache_create_usercopy, but commit 53944f171a89d
("mm: remove HARDENED_USERCOPY_FALLBACK") removed that check. To resolve this
issue, update the creation of the flash_block_cache to use
kmem_cache_create_usercopy with a default size of RTAS_BLK_SIZE.
Signed-off-by: Audra Mitchell <aubaker@xxxxxxxxxx>
---
arch/powerpc/kernel/rtas_flash.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
index a99179d83538..0a156a600f31 100644
--- a/arch/powerpc/kernel/rtas_flash.c
+++ b/arch/powerpc/kernel/rtas_flash.c
@@ -710,9 +710,9 @@ static int __init rtas_flash_init(void)
if (!rtas_validate_flash_data.buf)
return -ENOMEM;
- flash_block_cache = kmem_cache_create("rtas_flash_cache",
+ flash_block_cache = kmem_cache_create_usercopy("rtas_flash_cache",
RTAS_BLK_SIZE, RTAS_BLK_SIZE, 0,
- NULL);
+ 0, RTAS_BLK_SIZE, NULL);
if (!flash_block_cache) {
printk(KERN_ERR "%s: failed to create block cache\n",
__func__);
--
2.40.1