[PATCH v2 0/2] arm: kasan: support CONFIG_KASAN_VMALLOC

[PATCH v2 0/2] arm: kasan: support CONFIG_KASAN_VMALLOC

[Lecopzer Chen]

Since the framework of KASAN_VMALLOC is well-developed,
It's easy to support for ARM that simply not to map shadow of VMALLOC
area on kasan_init.

This can fix ARM_MODULE_PLTS with KASAN and provide first step
to support CONFIG_VMAP_STACK in ARM.
    

Patch base on v5.16

Test on
1. Qemu with memory 2G and vmalloc=500M for 3G/1G mapping.
2. Qemu with memory 2G and vmalloc=500M for 3G/1G mapping + LPAE.
3. Qemu with memory 2G and vmalloc=500M for 2G/2G mapping.


v2:
    rebase on 5.17-rc3


Lecopzer Chen (2):
  arm: kasan: support CONFIG_KASAN_VMALLOC
  arm: kconfig: fix MODULE_PLTS for KASAN with KASAN_VMALLOC

 arch/arm/Kconfig         | 2 ++
 arch/arm/mm/kasan_init.c | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

-- 
2.25.1

[PATCH v2 1/2] arm: kasan: support CONFIG_KASAN_VMALLOC

[Lecopzer Chen]

Simply make shadow of vmalloc area mapped on demand.

This can fix ARM_MODULE_PLTS with KASAN and provide first step
to support CONFIG_VMAP_STACK in ARM.

Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
---
 arch/arm/Kconfig         | 1 +
 arch/arm/mm/kasan_init.c | 6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4c97cb40eebb..78250e246cc6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -72,6 +72,7 @@ config ARM
 	select HAVE_ARCH_KFENCE if MMU && !XIP_KERNEL
 	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
 	select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
+	select HAVE_ARCH_KASAN_VMALLOC if HAVE_ARCH_KASAN
 	select HAVE_ARCH_MMAP_RND_BITS if MMU
 	select HAVE_ARCH_PFN_VALID
 	select HAVE_ARCH_SECCOMP
diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
index 5ad0d6c56d56..29caee9c79ce 100644
--- a/arch/arm/mm/kasan_init.c
+++ b/arch/arm/mm/kasan_init.c
@@ -236,7 +236,11 @@ void __init kasan_init(void)
 
 	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 
-	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
+	if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
+		kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
+					    kasan_mem_to_shadow((void *)VMALLOC_END));
+
+	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_END),
 				    kasan_mem_to_shadow((void *)-1UL) + 1);
 
 	for_each_mem_range(i, &pa_start, &pa_end) {
-- 
2.25.1

Re: [PATCH v2 1/2] arm: kasan: support CONFIG_KASAN_VMALLOC

[Linus Walleij]

Hi Lecopzer,

thanks for working on this! I need this support too.

On Sat, Feb 12, 2022 at 8:47 AM Lecopzer Chen
<lecopzer.chen@mediatek.com> wrote:

> Simply make shadow of vmalloc area mapped on demand.
>
> This can fix ARM_MODULE_PLTS with KASAN and provide first step
> to support CONFIG_VMAP_STACK in ARM.
>
> Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>

(...)

> -       kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
> +       if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
> +               kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
> +                                           kasan_mem_to_shadow((void *)VMALLOC_END));
> +
> +       kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_END),
>                                     kasan_mem_to_shadow((void *)-1UL) + 1);

Where is this actually mapped?

Can you print out where
kasan_mem_to_shadow((void *)VMALLOC_START)
kasan_mem_to_shadow((void *)VMALLOC_END)
as well as KASAN_SHADOW_START and KASAN_SHADOW_END
points?

When I looked into this getting the shadow memory between
KASAN_SHADOW_START and KASAN_SHADOW_END
seemed like the big problem since this is static, so how is Kasan
solving this now?

Please patch the picture in
include/asm/kasan_def.h
and the info in
Documentation/arm/memory.rst
so it clearly reflects where VMALLOC is shadowed.

Yours,
Linus Walleij

Re: [PATCH v2 1/2] arm: kasan: support CONFIG_KASAN_VMALLOC

[Lecopzer Chen]

Hi Linus
 
Thanks for your review.
 
> > -       kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
> > +       if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
> > +               kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
> > +                                           kasan_mem_to_shadow((void *)VMALLOC_END));
> > +
> > +       kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_END),
> >                                     kasan_mem_to_shadow((void *)-1UL) + 1);
> 
> Where is this actually mapped?
> 
> Can you print out where
> kasan_mem_to_shadow((void *)VMALLOC_START)
> kasan_mem_to_shadow((void *)VMALLOC_END)
> as well as KASAN_SHADOW_START and KASAN_SHADOW_END
> points?
> 
> When I looked into this getting the shadow memory between
> KASAN_SHADOW_START and KASAN_SHADOW_END
> seemed like the big problem since this is static, so how is Kasan
> solving this now?

For quick answer:
As I knwon, the definition of KASAN_SHADOW_START and END

(@arch/arm/include/asm/kasan_def.h)
* 1) KASAN_SHADOW_START
 *   This value begins with the MODULE_VADDR's shadow address. It is the
 *   start of kernel virtual space....
 *
 * 2) KASAN_SHADOW_END
 *   This value is the 0x100000000's shadow address: the mapping that would
 *   be after the end of the kernel memory at 0xffffffff....

and the virt address of vmalloc for ARM32 is also between MODULE_VADDR and
0x100000000 (ZONE_HIGHMEM), so nothing needs to do.

If there is any cases may break this assumption, please correct me, thanks.

> 
> Please patch the picture in
> include/asm/kasan_def.h
> and the info in
> Documentation/arm/memory.rst
> so it clearly reflects where VMALLOC is shadowed.

Thanks for suggestion, Yes, we really do need to update doc for memory layout.
I'll study how to add it and provide in v3.

[PATCH v2 2/2] arm: kconfig: fix MODULE_PLTS for KASAN with KASAN_VMALLOC

[Lecopzer Chen]

When we run out of module space address with ko insertion,
and with MODULE_PLTS, module would turn to try to find memory
from VMALLOC address space.

Unfortunately, with KASAN enabled, VMALLOC doesn't work without
KASAN_VMALLOC, thus select KASAN_VMALLOC by default.

8<--- cut here ---
 Unable to handle kernel paging request at virtual address bd300860
 [bd300860] *pgd=41cf1811, *pte=41cf26df, *ppte=41cf265f
 Internal error: Oops: 80f [#1] PREEMPT SMP ARM
 Modules linked in: hello(O+)
 CPU: 0 PID: 89 Comm: insmod Tainted: G           O      5.16.0-rc6+ #19
 Hardware name: Generic DT based system
 PC is at mmioset+0x30/0xa8
 LR is at 0x0
 pc : [<c077ed30>]    lr : [<00000000>]    psr: 20000013
 sp : c451fc18  ip : bd300860  fp : c451fc2c
 r10: f18042cc  r9 : f18042d0  r8 : 00000000
 r7 : 00000001  r6 : 00000003  r5 : 01312d00  r4 : f1804300
 r3 : 00000000  r2 : 00262560  r1 : 00000000  r0 : bd300860
 Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
 Control: 10c5387d  Table: 43e9406a  DAC: 00000051
 Register r0 information: non-paged memory
 Register r1 information: NULL pointer
 Register r2 information: non-paged memory
 Register r3 information: NULL pointer
 Register r4 information: 4887-page vmalloc region starting at 0xf1802000 allocated at load_module+0x14f4/0x32a8
 Register r5 information: non-paged memory
 Register r6 information: non-paged memory
 Register r7 information: non-paged memory
 Register r8 information: NULL pointer
 Register r9 information: 4887-page vmalloc region starting at 0xf1802000 allocated at load_module+0x14f4/0x32a8
 Register r10 information: 4887-page vmalloc region starting at 0xf1802000 allocated at load_module+0x14f4/0x32a8
 Register r11 information: non-slab/vmalloc memory
 Register r12 information: non-paged memory
 Process insmod (pid: 89, stack limit = 0xc451c000)
 Stack: (0xc451fc18 to 0xc4520000)
 fc00:                                                       f18041f0 c04803a4
 fc20: c451fc44 c451fc30 c048053c c0480358 f1804030 01312cff c451fc64 c451fc48
 fc40: c047f330 c0480500 f18040c0 c1b52ccc 00000001 c5be7700 c451fc74 c451fc68
 fc60: f1802098 c047f300 c451fcb4 c451fc78 c026106c f180208c c4880004 00000000
 fc80: c451fcb4 bf001000 c044ff48 c451fec0 f18040c0 00000000 c1b54cc4 00000000
 fca0: c451fdf0 f1804268 c451fe64 c451fcb8 c0264e88 c0260d48 ffff8000 00007fff
 fcc0: f18040c0 c025cd00 c451fd14 00000003 0157f008 f1804258 f180425c f1804174
 fce0: f1804154 f180424c f18041f0 f180414c f1804178 f18041c0 bf0025d4 188a3fa8
 fd00: 0000009e f1804170 f2b18000 c451ff10 c0d92e40 f180416c c451feec 00000001
 fd20: 00000000 c451fec8 c451fe20 c451fed0 f18040cc 00000000 f17ea000 c451fdc0
 fd40: 41b58ab3 c1387729 c0261c28 c047fb5c c451fe2c c451fd60 c0525308 c048033c
 fd60: 188a3fb4 c3ccb090 c451fe00 c3ccb080 00000000 00000000 00016920 00000000
 fd80: c02d0388 c047f55c c02d0388 00000000 c451fddc c451fda0 c02d0388 00000000
 fda0: 41b58ab3 c13a72d0 c0524ff0 c1705f48 c451fdfc c451fdc0 c02d0388 c047f55c
 fdc0: 00016920 00000000 00000003 c1bb2384 c451fdfc c3ccb080 c1bb2384 00000000
 fde0: 00000000 00000000 00000000 00000000 c451fe1c c451fe00 c04e9d70 c1705f48
 fe00: c1b54cc4 c1bbc71c c3ccb080 00000000 c3ccb080 00000000 00000003 c451fec0
 fe20: c451fe64 c451fe30 c0525918 c0524ffc c451feb0 c1705f48 00000000 c1b54cc4
 fe40: b78a3fd0 c451ff60 00000000 0157f008 00000003 c451fec0 c451ffa4 c451fe68
 fe60: c0265480 c0261c34 c451feb0 7fffffff 00000000 00000002 00000000 c4880000
 fe80: 41b58ab3 c138777b c02652cc c04803ec 000a0000 c451ff00 ffffff9c b6ac9f60
 fea0: c451fed4 c1705f48 c04a4a90 b78a3fdc f17ea000 ffffff9c b6ac9f60 c0100244
 fec0: f17ea21a f17ea300 f17ea000 00016920 f1800240 f18000ac f17fb7dc 01316000
 fee0: 013161b0 00002590 01316250 00000000 00000000 00000000 00002580 00000029
 ff00: 0000002a 00000013 00000000 0000000c 00000000 00000000 0157f004 c451ffb0
 ff20: c1719be0 aed6f410 c451ff74 c451ff38 c0c4103c c0c407d0 c451ff84 c451ff48
 ff40: 00000805 c02c8658 c1604230 c1719c30 00000805 0157f004 00000005 c451ffb0
 ff60: c1719be0 aed6f410 c451ffac c451ff78 c0122130 c1705f48 c451ffac 0157f008
 ff80: 00000006 0000005f 0000017b c0100244 c4880000 0000017b 00000000 c451ffa8
 ffa0: c0100060 c02652d8 0157f008 00000006 00000003 0157f008 00000000 b6ac9f60
 ffc0: 0157f008 00000006 0000005f 0000017b 00000000 00000000 aed85f74 00000000
 ffe0: b6ac9cd8 b6ac9cc8 00030200 aecf2d60 a0000010 00000003 00000000 00000000
 Backtrace:
 [<c048034c>] (kasan_poison) from [<c048053c>] (kasan_unpoison+0x48/0x5c)
 [<c04804f4>] (kasan_unpoison) from [<c047f330>] (__asan_register_globals+0x3c/0x64)
  r5:01312cff r4:f1804030
 [<c047f2f4>] (__asan_register_globals) from [<f1802098>] (_sub_I_65535_1+0x18/0xf80 [hello])
  r7:c5be7700 r6:00000001 r5:c1b52ccc r4:f18040c0
 [<f1802080>] (_sub_I_65535_1 [hello]) from [<c026106c>] (do_init_module+0x330/0x72c)
 [<c0260d3c>] (do_init_module) from [<c0264e88>] (load_module+0x3260/0x32a8)
  r10:f1804268 r9:c451fdf0 r8:00000000 r7:c1b54cc4 r6:00000000 r5:f18040c0
  r4:c451fec0
 [<c0261c28>] (load_module) from [<c0265480>] (sys_finit_module+0x1b4/0x1e8)
  r10:c451fec0 r9:00000003 r8:0157f008 r7:00000000 r6:c451ff60 r5:b78a3fd0
  r4:c1b54cc4
 [<c02652cc>] (sys_finit_module) from [<c0100060>] (ret_fast_syscall+0x0/0x1c)
 Exception stack(0xc451ffa8 to 0xc451fff0)
 ffa0:                   0157f008 00000006 00000003 0157f008 00000000 b6ac9f60
 ffc0: 0157f008 00000006 0000005f 0000017b 00000000 00000000 aed85f74 00000000
 ffe0: b6ac9cd8 b6ac9cc8 00030200 aecf2d60
  r10:0000017b r9:c4880000 r8:c0100244 r7:0000017b r6:0000005f r5:00000006
  r4:0157f008
 Code: e92d4100 e1a08001 e1a0e003 e2522040 (a8ac410a)
 ---[ end trace df6e12843197b6f5 ]---

Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
---
 arch/arm/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 78250e246cc6..d797a3699959 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1515,6 +1515,7 @@ config ARCH_WANT_GENERAL_HUGETLB
 config ARM_MODULE_PLTS
 	bool "Use PLTs to allow module memory to spill over into vmalloc area"
 	depends on MODULES
+	select KASAN_VMALLOC if KASAN
 	default y
 	help
 	  Allocate PLTs when loading modules so that jumps and calls whose
-- 
2.25.1