Messages in this thread | | | From | Atish Patra <> | Date | Mon, 12 Oct 2020 18:28:10 -0700 | Subject | Re: [PATCH 4/5] RISC-V: Protect .init.text & .init.data |
| |
On Mon, Oct 12, 2020 at 4:26 PM Atish Patra <atishp@atishpatra.org> wrote: > > On Mon, Oct 12, 2020 at 6:15 AM Greentime Hu <greentime.hu@sifive.com> wrote: > > > > 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 > > > > Thanks for testing the patch. > > > [ 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 > > > > This would be triggered for the current kernel as well as we don't > protect the permission for __init section at all. As you correctly > pointed out, __init & .head sections are mapped with same permissions > because of 2MB mappings. > > Currently, the entire head.text & init section have RWX permission. > This patch is trying remove the write permission from .init.text & > .head.text and execute permission from .init.data until kernel is > booted. > It doesn't provide full protection but better than the current scheme. > > To remove the write permission of .head.txt only, we have to keep > .head.txt & .init.text section in separate sections. The linear > mapping would look like this in that case. > There are no issues as such but kernel size would increase by another 2M. > > ---[ Linear mapping ]--- > 0xffffffe000000000-0xffffffe000200000 0x0000000080200000 2M > PMD D A . . X . R V > 0xffffffe000200000-0xffffffe000600000 0x0000000080400000 4M > PMD D A . . . W R V > 0xffffffe000600000-0xffffffe000e00000 0x0000000080800000 8M > PMD D A . . X . R V > 0xffffffe000e00000-0xffffffe001400000 0x0000000081000000 6M > PMD D A . . . . R V > 0xffffffe001400000-0xffffffe03fe00000 0x0000000081600000 1002M > PMD D A . . . W R V > > The other solution would be move init section below text. Keep text & > head in one section. > The .init.text & .init.data will be in separate sections after that. > Here is the mapping in that case. > > ---[ Linear mapping ]--- > 0xffffffe000000000-0xffffffe000800000 0x0000000080200000 8M > PMD D A . . X . R V > 0xffffffe000800000-0xffffffe000c00000 0x0000000080a00000 4M > PMD D A . . . W R V > 0xffffffe000c00000-0xffffffe001200000 0x0000000080e00000 6M > PMD D A . . . . R V > 0xffffffe001200000-0xffffffe03fe00000 0x0000000081400000 1004M > PMD D A . . . W R V > > I prefer the 2nd approach compared to the first one as it saves memory > and we can fix lockdep issue without adding arch_is_kernel_data > to sections.h (Guo's patch). > > However, the 2nd approach throws this problem if > CONFIG_HARDENED_USERCOPY is enabled. > > net/ipv4/ipconfig.o: in function `ic_setup_routes': > /home/atish/workspace/linux/net/ipv4/ipconfig.c:400:(.init.text+0x1c4): > relocation truncated to fit: R_RISCV_JAL against symbol `ip_rt_ioctl' > defined in .text section in net/ipv4/fib_frontend.o > make: *** [Makefile:1162: vmlinux] Error 1 > > I am currently looking into this to understand why R_RISCV_JAL is > generated a generic function invocation > where auipc + jalr should have been used. >
I checked the relocation is is correct 00000000000001d0 R_RISCV_CALL ip_rt_ioctl The assembly from objdump also shows a pair of auipc + jalr.
1d0: 00000097 auipc ra,0x0 1d4: 000080e7 jalr ra # 1d0 <.LBE348+0x4>
I don't understand why the toolchain is complaining about relocation error only when CONFIG_HARDENED_USERCOPY is enabled.
Are we seeing some subtle toolchain bug ?
> > 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? > > > > _______________________________________________ > > linux-riscv mailing list > > linux-riscv@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-riscv > > > > -- > Regards, > Atish
-- Regards, Atish
| |