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Mon, 31 Jan 2022 04:14:39 -0800 (PST) MIME-Version: 1.0 References: <20220131105215.644174521@linuxfoundation.org> <20220131105216.796938973@linuxfoundation.org> In-Reply-To: <20220131105216.796938973@linuxfoundation.org> From: Ard Biesheuvel Date: Mon, 31 Jan 2022 13:14:28 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 5.4 33/64] ARM: 9170/1: fix panic when kasan and kprobe are enabled To: Greg Kroah-Hartman Cc: Linux Kernel Mailing List , "# 3.4.x" , huangshaobo , "Russell King (Oracle)" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 31 Jan 2022 at 11:59, Greg Kroah-Hartman wrote: > > From: sparkhuang > > commit 8b59b0a53c840921b625378f137e88adfa87647e upstream. > > arm32 uses software to simulate the instruction replaced > by kprobe. some instructions may be simulated by constructing > assembly functions. therefore, before executing instruction > simulation, it is necessary to construct assembly function > execution environment in C language through binding registers. > after kasan is enabled, the register binding relationship will > be destroyed, resulting in instruction simulation errors and > causing kernel panic. > > the kprobe emulate instruction function is distributed in three > files: actions-common.c actions-arm.c actions-thumb.c, so disable > KASAN when compiling these files. > > for example, use kprobe insert on cap_capable+20 after kasan > enabled, the cap_capable assembly code is as follows: > : > e92d47f0 push {r4, r5, r6, r7, r8, r9, sl, lr} > e1a05000 mov r5, r0 > e280006c add r0, r0, #108 ; 0x6c > e1a04001 mov r4, r1 > e1a06002 mov r6, r2 > e59fa090 ldr sl, [pc, #144] ; > ebfc7bf8 bl c03aa4b4 <__asan_load4> > e595706c ldr r7, [r5, #108] ; 0x6c > e2859014 add r9, r5, #20 > ...... > The emulate_ldr assembly code after enabling kasan is as follows: > c06f1384 : > e92d47f0 push {r4, r5, r6, r7, r8, r9, sl, lr} > e282803c add r8, r2, #60 ; 0x3c > e1a05000 mov r5, r0 > e7e37855 ubfx r7, r5, #16, #4 > e1a00008 mov r0, r8 > e1a09001 mov r9, r1 > e1a04002 mov r4, r2 > ebf35462 bl c03c6530 <__asan_load4> > e357000f cmp r7, #15 > e7e36655 ubfx r6, r5, #12, #4 > e205a00f and sl, r5, #15 > 0a000001 beq c06f13bc > e0840107 add r0, r4, r7, lsl #2 > ebf3545c bl c03c6530 <__asan_load4> > e084010a add r0, r4, sl, lsl #2 > ebf3545a bl c03c6530 <__asan_load4> > e2890010 add r0, r9, #16 > ebf35458 bl c03c6530 <__asan_load4> > e5990010 ldr r0, [r9, #16] > e12fff30 blx r0 > e356000f cm r6, #15 > 1a000014 bne c06f1430 > e1a06000 mov r6, r0 > e2840040 add r0, r4, #64 ; 0x40 > ...... > > when running in emulate_ldr to simulate the ldr instruction, panic > occurred, and the log is as follows: > Unable to handle kernel NULL pointer dereference at virtual address > 00000090 > pgd = ecb46400 > [00000090] *pgd=2e0fa003, *pmd=00000000 > Internal error: Oops: 206 [#1] SMP ARM > PC is at cap_capable+0x14/0xb0 > LR is at emulate_ldr+0x50/0xc0 > psr: 600d0293 sp : ecd63af8 ip : 00000004 fp : c0a7c30c > r10: 00000000 r9 : c30897f4 r8 : ecd63cd4 > r7 : 0000000f r6 : 0000000a r5 : e59fa090 r4 : ecd63c98 > r3 : c06ae294 r2 : 00000000 r1 : b7611300 r0 : bf4ec008 > Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user > Control: 32c5387d Table: 2d546400 DAC: 55555555 > Process bash (pid: 1643, stack limit = 0xecd60190) > (cap_capable) from (kprobe_handler+0x218/0x340) > (kprobe_handler) from (kprobe_trap_handler+0x24/0x48) > (kprobe_trap_handler) from (do_undefinstr+0x13c/0x364) > (do_undefinstr) from (__und_svc_finish+0x0/0x30) > (__und_svc_finish) from (cap_capable+0x18/0xb0) > (cap_capable) from (cap_vm_enough_memory+0x38/0x48) > (cap_vm_enough_memory) from > (security_vm_enough_memory_mm+0x48/0x6c) > (security_vm_enough_memory_mm) from > (copy_process.constprop.5+0x16b4/0x25c8) > (copy_process.constprop.5) from (_do_fork+0xe8/0x55c) > (_do_fork) from (SyS_clone+0x1c/0x24) > (SyS_clone) from (__sys_trace_return+0x0/0x10) > Code: 0050a0e1 6c0080e2 0140a0e1 0260a0e1 (f801f0e7) > > Fixes: 35aa1df43283 ("ARM kprobes: instruction single-stepping support") > Fixes: 421015713b30 ("ARM: 9017/2: Enable KASan for ARM") > Signed-off-by: huangshaobo > Acked-by: Ard Biesheuvel > Signed-off-by: Russell King (Oracle) > Signed-off-by: Greg Kroah-Hartman Probably a bit late to mention this but v5.4 does not support KASAN on ARM, so this patch is fairly pointless. > --- > arch/arm/probes/kprobes/Makefile | 3 +++ > 1 file changed, 3 insertions(+) > > --- a/arch/arm/probes/kprobes/Makefile > +++ b/arch/arm/probes/kprobes/Makefile > @@ -1,4 +1,7 @@ > # SPDX-License-Identifier: GPL-2.0 > +KASAN_SANITIZE_actions-common.o := n > +KASAN_SANITIZE_actions-arm.o := n > +KASAN_SANITIZE_actions-thumb.o := n > obj-$(CONFIG_KPROBES) += core.o actions-common.o checkers-common.o > obj-$(CONFIG_ARM_KPROBES_TEST) += test-kprobes.o > test-kprobes-objs := test-core.o > >