Messages in this thread | | | From | Atish Patra <> | Date | Tue, 13 Oct 2020 15:25:18 -0700 | Subject | Re: [PATCH 4/5] RISC-V: Protect .init.text & .init.data |
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On Mon, Oct 12, 2020 at 8:08 PM Greentime Hu <greentime.hu@sifive.com> wrote: > > Atish Patra <atishp@atishpatra.org> 於 2020年10月13日 週二 上午9:28寫道: > > > > 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 ? > > > "relocation truncated to fit" usually means that the jump address is > too far to jump. > Maybe trying "-mno-relax -Wl,--no-relax" to disable linker relax or > checking if somewhere just using jal instead of call?
Yes. As I said the relocation id seems correct from the objdump. I narrowed down the issue to a __builtin_constant_p
Here is the code path: ip_rt_ioctl->rtentry_to_fib_config->copy_from_user->check_copy_size->check_object_size
#ifdef CONFIG_HARDENED_USERCOPY 112 extern void __check_object_size(const void *ptr, unsigned long n, 113 bool to_user); 114 115 static __always_inline void check_object_size(const void *ptr, unsigned long n, 116 bool to_user) 117 { 118 if (!__builtin_constant_p(n)) ---------------------> Commenting this line avoids the linker issue
119 __check_object_size(ptr, n, to_user); 120 } 121 #else 122 static inline void check_object_size(const void *ptr, unsigned long n, 123 bool to_user) 124 { } 125 #endif /* CONFIG_HARDENED_USERCOPY */
This happens only when copy_from_user is called from function that is annotated with __init. Adding Kito & Jim for their input
@kito, @Jim: Please let me know if I should create a issue in riscv-gnu-toolchain repo or somewhere else.
-- Regards, Atish
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