[PATCH] ARM: fix panic when kasan and kprobe are enabled
Shaobo Huang
huangshaobo6 at huawei.com
Mon Jul 19 00:45:38 PDT 2021
On Mon, 19 Jul 2021 at 07:06, Ard Biesheuvel <ardb at kernel.org> wrote:
> On Mon, 19 Jul 2021 at 05:09, Shaobo Huang <huangshaobo6 at huawei.com> wrote:
> >
> > On Sat, 17 Jul 2021 at 01:01, Ard Biesheuvel <ardb at kernel.org> wrote:
> > > On Wed, 14 Jul 2021 at 10:27, Shaobo Huang <huangshaobo6 at huawei.com> wrote:
> > >>
> > >> From: huangshaobo <huangshaobo6 at huawei.com>
> > >>
> > >> 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:
> > >> <cap_capable>:
> > >> 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 <emulate_ldr>:
> > >> 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 <emulate_ldr+0x38>
> > >> 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 <emulate_ldr+0xac>
> > >> 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 <huangshaobo6 at huawei.com>
> > >> Asked-by: Ard Biesheuvel <ardb at kernel.org>
> > >
> > > Please don't do this - the maintainer will pick it up when applying,
> > > or when you send a new version of the patch, it is OK to add these
> > > tags if you have not made any substantial changes.
> > >
> > > But please do *not* add tags like this on someone else's behalf by
> > > replying to the email - and I should also point out that 'asked-by' is
> > > bogus.
> > >
> >
> > Hi ardb,
> > 1.The original patch you have been asked-by by email before, link: https://lore.kernel.org/linux-arm-kernel/CAMj1kXGqfF68MT4WwrxS0cYiUBb0gODDh-wGZSQcW9vxdfK90A@mail.gmail.com/
>
> No it was not.
>
> It was ACKed by, not ASKed by.
>
> > 2.In addition to adding the asked-by tag, there is no other content modification in this patch
> > 3.The patch was reissued because the previous recipient did not include kasan maintainer and reviewers
> >
>
> I don't care. Do NOT reply to emails with tags in other people's names.
>
Hi ardb,
Sincerely apologize for my mistake,
I mistakenly wrote the Acked-by label as Asked-by.
Do I need to change to Acked-by or remove the label and reissue a patch?
thanks,
Shaobo Huang
>
> > thanks,
> > ShaoBo Huang
> >
> > >
> > >> ---
> > >> arch/arm/probes/kprobes/Makefile | 3 +++
> > >> 1 file changed, 3 insertions(+)
> > >>
> > >> diff --git a/arch/arm/probes/kprobes/Makefile b/arch/arm/probes/kprobes/Makefile
> > >> index 14db56f49f0a..6159010dac4a 100644
> > >> --- 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
> > >> --
> > >> 2.12.3
> > >>
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