Messages in this thread | | | From | Greentime Hu <> | Date | Mon, 12 Oct 2020 21:14:50 +0800 | Subject | Re: [PATCH 4/5] RISC-V: Protect .init.text & .init.data |
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Atish Patra <atish.patra@wdc.com> 於 2020年10月10日 週六 上午5:13寫道: > > Currently, .init.text & .init.data are intermixed which makes it impossible > apply different permissions to them. .init.data shouldn't need exec > permissions while .init.text shouldn't have write permission. > > Keep them in separate sections so that different permissions are applied to > each section. This improves the kernel protection under > CONFIG_STRICT_KERNEL_RWX. We also need to restore the permissions for the > entire _init section after it is freed so that those pages can be used for > other purpose. > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > --- > arch/riscv/include/asm/sections.h | 2 ++ > arch/riscv/include/asm/set_memory.h | 2 ++ > arch/riscv/kernel/setup.c | 4 ++++ > arch/riscv/kernel/vmlinux.lds.S | 10 +++++++++- > arch/riscv/mm/init.c | 6 ++++++ > arch/riscv/mm/pageattr.c | 6 ++++++ > 6 files changed, 29 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/include/asm/sections.h b/arch/riscv/include/asm/sections.h > index d60802bfafbc..730d2c4a844d 100644 > --- a/arch/riscv/include/asm/sections.h > +++ b/arch/riscv/include/asm/sections.h > @@ -10,6 +10,8 @@ > #include <asm-generic/sections.h> > extern char _start[]; > extern char _start_kernel[]; > +extern char __init_data_begin[], __init_data_end[]; > +extern char __init_text_begin[], __init_text_end[]; > > extern bool init_mem_is_free; > > diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h > index 4cc3a4e2afd3..913429c9c1ae 100644 > --- a/arch/riscv/include/asm/set_memory.h > +++ b/arch/riscv/include/asm/set_memory.h > @@ -15,6 +15,7 @@ int set_memory_ro(unsigned long addr, int numpages); > int set_memory_rw(unsigned long addr, int numpages); > int set_memory_x(unsigned long addr, int numpages); > int set_memory_nx(unsigned long addr, int numpages); > +int set_memory_default(unsigned long addr, int numpages); > void protect_kernel_text_data(void); > #else > static inline int set_memory_ro(unsigned long addr, int numpages) { return 0; } > @@ -22,6 +23,7 @@ static inline int set_memory_rw(unsigned long addr, int numpages) { return 0; } > static inline int set_memory_x(unsigned long addr, int numpages) { return 0; } > static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; } > static inline void protect_kernel_text_data(void) {}; > +static inline int set_memory_default(unsigned long addr, int numpages) { return 0; } > #endif > > int set_direct_map_invalid_noflush(struct page *page); > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index 4176a2affd1d..b8a35ef0eab0 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -129,6 +129,10 @@ bool init_mem_is_free = false; > > void free_initmem(void) > { > + unsigned long init_begin = (unsigned long)__init_begin; > + unsigned long init_end = (unsigned long)__init_end; > + > + set_memory_default(init_begin, (init_end - init_begin) >> PAGE_SHIFT); > free_initmem_default(POISON_FREE_INITMEM); > init_mem_is_free = true; > } > diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S > index 0807633f0dc8..15b9882588ae 100644 > --- a/arch/riscv/kernel/vmlinux.lds.S > +++ b/arch/riscv/kernel/vmlinux.lds.S > @@ -30,8 +30,8 @@ SECTIONS > . = ALIGN(PAGE_SIZE); > > __init_begin = .; > + __init_text_begin = .; > INIT_TEXT_SECTION(PAGE_SIZE) > - INIT_DATA_SECTION(16) > . = ALIGN(8); > __soc_early_init_table : { > __soc_early_init_table_start = .; > @@ -48,11 +48,19 @@ SECTIONS > { > EXIT_TEXT > } > + > + __init_text_end = .; > + . = ALIGN(SECTION_ALIGN); > + /* Start of init data section */ > + __init_data_begin = .; > + INIT_DATA_SECTION(16) > .exit.data : > { > EXIT_DATA > } > PERCPU_SECTION(L1_CACHE_BYTES) > + > + __init_data_end = .; > __init_end = .; > > . = ALIGN(SECTION_ALIGN); > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 7859a1d1b34d..3ef0eafcc7c7 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -627,11 +627,17 @@ void protect_kernel_text_data(void) > { > unsigned long text_start = (unsigned long)_text; > unsigned long text_end = (unsigned long)_etext; > + unsigned long init_text_start = (unsigned long)__init_text_begin; > + unsigned long init_text_end = (unsigned long)__init_text_end; > + unsigned long init_data_start = (unsigned long)__init_data_begin; > + unsigned long init_data_end = (unsigned long)__init_data_end; > unsigned long rodata_start = (unsigned long)__start_rodata; > unsigned long data_start = (unsigned long)_data; > unsigned long max_low = (unsigned long)(__va(PFN_PHYS(max_low_pfn))); > > + set_memory_ro(init_text_start, (init_text_end - init_text_start) >> PAGE_SHIFT); > set_memory_ro(text_start, (text_end - text_start) >> PAGE_SHIFT); > + set_memory_nx(init_data_start, (init_data_end - init_data_start) >> PAGE_SHIFT); > set_memory_nx(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT); > set_memory_nx(data_start, (max_low - data_start) >> PAGE_SHIFT); > } > diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c > index 19fecb362d81..aecedaf086ab 100644 > --- a/arch/riscv/mm/pageattr.c > +++ b/arch/riscv/mm/pageattr.c > @@ -128,6 +128,12 @@ static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask, > return ret; > } > > +int set_memory_default(unsigned long addr, int numpages) > +{ > + return __set_memory(addr, numpages, __pgprot(_PAGE_KERNEL | _PAGE_EXEC), > + __pgprot(0)); > +} > + > int set_memory_ro(unsigned long addr, int numpages) > { > return __set_memory(addr, numpages, __pgprot(_PAGE_READ),
Hi Atish,
I tested this patchset and CONFIG_DEBUG_WX=y
[ 2.664012] Freeing unused kernel memory: 114420K [ 2.666081] ------------[ cut here ]------------ [ 2.666779] riscv/mm: Found insecure W+X mapping at address (____ptrval____)/0xffffffe000000000 [ 2.668004] WARNING: CPU: 0 PID: 1 at arch/riscv/mm/ptdump.c:200 note_page+0xc2/0x238 [ 2.669147] Modules linked in: [ 2.669735] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc8-00033-gfacf070a80ea #153 [ 2.670466] epc: ffffffe00700697c ra : ffffffe00700697c sp : ffffffe0fba9bc10 [ 2.671054] gp : ffffffe007e73078 tp : ffffffe0fba90000 t0 : ffffffe007e861d0 [ 2.671683] t1 : 0000000000000064 t2 : ffffffe007801664 s0 : ffffffe0fba9bc60 [ 2.672499] s1 : ffffffe0fba9bde8 a0 : 0000000000000053 a1 : 0000000000000020 [ 2.673119] a2 : 0000000000000000 a3 : 00000000000000f4 a4 : d4328dc070ccb100 [ 2.673729] a5 : d4328dc070ccb100 a6 : 0000000000000000 a7 : ffffffe007851e98 [ 2.674333] s2 : ffffffe007000000 s3 : ffffffe0fba9bde8 s4 : 0000000087200000 [ 2.674963] s5 : 00000000000000cb s6 : 0000000000000003 s7 : ffffffe007e7ac00 [ 2.675564] s8 : ffffffe000000000 s9 : ffffffe007000000 s10: ffffffe000000000 [ 2.676392] s11: ffffffe040000000 t3 : 000000000001da48 t4 : 000000000001da48 [ 2.676992] t5 : ffffffe007e74490 t6 : ffffffe007e81432 [ 2.677449] status: 0000000000000120 badaddr: 0000000000000000 cause: 0000000000000003 [ 2.678128] ---[ end trace 5f0a86dbe986db9b ]--- [ 2.678952] Checked W+X mappings: failed, 28672 W+X pages found [ 2.679737] Run /init as init process
After debugging, I found it is because set_memory_ro()/set_memory_nx()/... can't handle the 4KB-aligned address if it is a 2MB mapping address. For example, if we gave 0xffffffe000001000 and this address is in a PMD mapping which is 2MB mapping, it will set the page attributes from 0xffffffe000000000. And this caused the CPU hotplug failed because it is in head.text section.
#0 pageattr_pmd_entry (pmd=0xffffffe0ffdff000, addr=18446743936270602240, next=18446743936270766080, walk=0xffffffe007e03e98) at arch/riscv/mm/pageattr.c:70 70 pmd_t val = READ_ONCE(*pmd); => 0xffffffe007005e96 <pageattr_pmd_entry+0>: 41 11 addi sp,sp,-16 0xffffffe007005e98 <pageattr_pmd_entry+2>: 22 e4 sd s0,8(sp) 0xffffffe007005e9a <pageattr_pmd_entry+4>: 00 08 addi s0,sp,16 0xffffffe007005e9c <pageattr_pmd_entry+6>: 1c 61 ld a5,0(a0) (gdb) p/x addr $21 = 0xffffffe000001000
# cat /sys/kernel/debug/kernel_page_tables ---[ Fixmap start ]--- 0xffffffcefef00000-0xffffffceff000000 0x0000000082200000 1M PTE D A . . . W R V ---[ Fixmap end ]--- ---[ PCI I/O start ]--- ---[ PCI I/O end ]--- ---[ vmalloc() area ]--- 0xffffffd000090000-0xffffffd000093000 0x00000001741bb000 12K PTE D A . . . W R V 0xffffffdffffbb000-0xffffffdffffbe000 0x0000000175f97000 12K PTE D A . . . W R V 0xffffffdffffcc000-0xffffffdffffcf000 0x0000000175f9a000 12K PTE D A . . . W R V 0xffffffdffffdd000-0xffffffdffffe0000 0x0000000175f9d000 12K PTE D A . . . W R V 0xffffffdffffee000-0xffffffdfffff1000 0x0000000175fa0000 12K PTE D A . . . W R V ---[ vmalloc() end ]--- ---[ Linear mapping ]--- 0xffffffe000000000-0xffffffe007000000 0x0000000080200000 112M PMD D A . . X W R V ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 0xffffffe007000000-0xffffffe007800000 0x0000000087200000 8M PMD D A . . X . R V 0xffffffe007800000-0xffffffe007e00000 0x0000000087a00000 6M PMD D A . . . . R V 0xffffffe007e00000-0xffffffe0ffe00000 0x0000000088000000 3968M PMD D A . . . W R V #
Any idea?
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