| From f2d35dea482df603137f7febbcd49ba1a3fac1dc Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 3 Feb 2025 11:14:57 +0100 |
| Subject: powerpc/code-patching: Disable KASAN report during patching via |
| temporary mm |
| |
| From: Christophe Leroy <christophe.leroy@csgroup.eu> |
| |
| [ Upstream commit dc9c5166c3cb044f8a001e397195242fd6796eee ] |
| |
| Erhard reports the following KASAN hit on Talos II (power9) with kernel 6.13: |
| |
| [ 12.028126] ================================================================== |
| [ 12.028198] BUG: KASAN: user-memory-access in copy_to_kernel_nofault+0x8c/0x1a0 |
| [ 12.028260] Write of size 8 at addr 0000187e458f2000 by task systemd/1 |
| |
| [ 12.028346] CPU: 87 UID: 0 PID: 1 Comm: systemd Tainted: G T 6.13.0-P9-dirty #3 |
| [ 12.028408] Tainted: [T]=RANDSTRUCT |
| [ 12.028446] Hardware name: T2P9D01 REV 1.01 POWER9 0x4e1202 opal:skiboot-bc106a0 PowerNV |
| [ 12.028500] Call Trace: |
| [ 12.028536] [c000000008dbf3b0] [c000000001656a48] dump_stack_lvl+0xbc/0x110 (unreliable) |
| [ 12.028609] [c000000008dbf3f0] [c0000000006e2fc8] print_report+0x6b0/0x708 |
| [ 12.028666] [c000000008dbf4e0] [c0000000006e2454] kasan_report+0x164/0x300 |
| [ 12.028725] [c000000008dbf600] [c0000000006e54d4] kasan_check_range+0x314/0x370 |
| [ 12.028784] [c000000008dbf640] [c0000000006e6310] __kasan_check_write+0x20/0x40 |
| [ 12.028842] [c000000008dbf660] [c000000000578e8c] copy_to_kernel_nofault+0x8c/0x1a0 |
| [ 12.028902] [c000000008dbf6a0] [c0000000000acfe4] __patch_instructions+0x194/0x210 |
| [ 12.028965] [c000000008dbf6e0] [c0000000000ade80] patch_instructions+0x150/0x590 |
| [ 12.029026] [c000000008dbf7c0] [c0000000001159bc] bpf_arch_text_copy+0x6c/0xe0 |
| [ 12.029085] [c000000008dbf800] [c000000000424250] bpf_jit_binary_pack_finalize+0x40/0xc0 |
| [ 12.029147] [c000000008dbf830] [c000000000115dec] bpf_int_jit_compile+0x3bc/0x930 |
| [ 12.029206] [c000000008dbf990] [c000000000423720] bpf_prog_select_runtime+0x1f0/0x280 |
| [ 12.029266] [c000000008dbfa00] [c000000000434b18] bpf_prog_load+0xbb8/0x1370 |
| [ 12.029324] [c000000008dbfb70] [c000000000436ebc] __sys_bpf+0x5ac/0x2e00 |
| [ 12.029379] [c000000008dbfd00] [c00000000043a228] sys_bpf+0x28/0x40 |
| [ 12.029435] [c000000008dbfd20] [c000000000038eb4] system_call_exception+0x334/0x610 |
| [ 12.029497] [c000000008dbfe50] [c00000000000c270] system_call_vectored_common+0xf0/0x280 |
| [ 12.029561] --- interrupt: 3000 at 0x3fff82f5cfa8 |
| [ 12.029608] NIP: 00003fff82f5cfa8 LR: 00003fff82f5cfa8 CTR: 0000000000000000 |
| [ 12.029660] REGS: c000000008dbfe80 TRAP: 3000 Tainted: G T (6.13.0-P9-dirty) |
| [ 12.029735] MSR: 900000000280f032 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI> CR: 42004848 XER: 00000000 |
| [ 12.029855] IRQMASK: 0 |
| GPR00: 0000000000000169 00003fffdcf789a0 00003fff83067100 0000000000000005 |
| GPR04: 00003fffdcf78a98 0000000000000090 0000000000000000 0000000000000008 |
| GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 |
| GPR12: 0000000000000000 00003fff836ff7e0 c000000000010678 0000000000000000 |
| GPR16: 0000000000000000 0000000000000000 00003fffdcf78f28 00003fffdcf78f90 |
| GPR20: 0000000000000000 0000000000000000 0000000000000000 00003fffdcf78f80 |
| GPR24: 00003fffdcf78f70 00003fffdcf78d10 00003fff835c7239 00003fffdcf78bd8 |
| GPR28: 00003fffdcf78a98 0000000000000000 0000000000000000 000000011f547580 |
| [ 12.030316] NIP [00003fff82f5cfa8] 0x3fff82f5cfa8 |
| [ 12.030361] LR [00003fff82f5cfa8] 0x3fff82f5cfa8 |
| [ 12.030405] --- interrupt: 3000 |
| [ 12.030444] ================================================================== |
| |
| Commit c28c15b6d28a ("powerpc/code-patching: Use temporary mm for |
| Radix MMU") is inspired from x86 but unlike x86 is doesn't disable |
| KASAN reports during patching. This wasn't a problem at the begining |
| because __patch_mem() is not instrumented. |
| |
| Commit 465cabc97b42 ("powerpc/code-patching: introduce |
| patch_instructions()") use copy_to_kernel_nofault() to copy several |
| instructions at once. But when using temporary mm the destination is |
| not regular kernel memory but a kind of kernel-like memory located |
| in user address space. Because it is not in kernel address space it is |
| not covered by KASAN shadow memory. Since commit e4137f08816b ("mm, |
| kasan, kmsan: instrument copy_from/to_kernel_nofault") KASAN reports |
| bad accesses from copy_to_kernel_nofault(). Here a bad access to user |
| memory is reported because KASAN detects the lack of shadow memory and |
| the address is below TASK_SIZE. |
| |
| Do like x86 in commit b3fd8e83ada0 ("x86/alternatives: Use temporary |
| mm for text poking") and disable KASAN reports during patching when |
| using temporary mm. |
| |
| Reported-by: Erhard Furtner <erhard_f@mailbox.org> |
| Close: https://lore.kernel.org/all/20250201151435.48400261@yea/ |
| Fixes: 465cabc97b42 ("powerpc/code-patching: introduce patch_instructions()") |
| Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> |
| Acked-by: Michael Ellerman <mpe@ellerman.id.au> |
| Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com> |
| Link: https://patch.msgid.link/1c05b2a1b02ad75b981cfc45927e0b4a90441046.1738577687.git.christophe.leroy@csgroup.eu |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/powerpc/lib/code-patching.c | 2 ++ |
| 1 file changed, 2 insertions(+) |
| |
| diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c |
| index acdab294b340a..2685d7efea511 100644 |
| --- a/arch/powerpc/lib/code-patching.c |
| +++ b/arch/powerpc/lib/code-patching.c |
| @@ -493,7 +493,9 @@ static int __do_patch_instructions_mm(u32 *addr, u32 *code, size_t len, bool rep |
| |
| orig_mm = start_using_temp_mm(patching_mm); |
| |
| + kasan_disable_current(); |
| err = __patch_instructions(patch_addr, code, len, repeat_instr); |
| + kasan_enable_current(); |
| |
| /* context synchronisation performed by __patch_instructions */ |
| stop_using_temp_mm(patching_mm, orig_mm); |
| -- |
| 2.39.5 |
| |
