On 02/09/2022 11:13, Vladimir Isaev wrote:
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>
> It is possible to have more than one mm (init_mm) during memory
> permission fixes. In my case it was caused by request_module
> from drivers/net/phy/phy_device.c and leads to following Oops
> during free_initmem() on RV32 platform:
> Unable to handle kernel paging request at virtual address c0800000
> Oops [#1]
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper Not tainted 5.15.45
> Hardware name: Syntacore SCR5 SDK board (DT)
> epc : __memset+0x58/0xf4
> ra : free_reserved_area+0xfa/0x15a
> epc : c02b26ac ra : c00eb588 sp : c1c1fed0
> gp : c1898690 tp : c1c98000 t0 : c0800000
> t1 : ffffffff t2 : 00000000 s0 : c1c1ff20
> s1 : c189a000 a0 : c0800000 a1 : cccccccc
> a2 : 00001000 a3 : c0801000 a4 : 00000000
> a5 : 00800000 a6 : fef09000 a7 : 00000000
> s2 : c0e57000 s3 : c10edcf8 s4 : 000000cc
> s5 : ffffefff s6 : c188a9f4 s7 : 00000001
> s8 : c0800000 s9 : fef1b000 s10: c10ee000
> s11: c189a000 t3 : 00000000 t4 : 00000000
> t5 : 00000000 t6 : 00000001
> status: 00000120 badaddr: c0800000 cause: 0000000f
> [<c0488658>] free_initmem+0x204/0x222
> [<c048d05a>] kernel_init+0x32/0xfc
> [<c0002f76>] ret_from_exception+0x0/0xc
> ---[ end trace 7a5e2b002350b528 ]---
>
> This is because request_module attempted to modprobe module, so it created
> new mm with the copy of kernel's page table. And this copy won't be updated
> in case of 4M pages and RV32 (pgd is the leaf).
>
> To fix this we can update protection bits for all of existing mm-s, the
> same as ARM does, see commit 08925c2f124f
> ("ARM: 8464/1: Update all mm structures with section adjustments").
>
> Fixes: 19a00869028f ("RISC-V: Protect all kernel sections including init early")
> Signed-off-by: Vladimir Isaev <vladimir.isaev@xxxxxxxxxxxxx>
> Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> ---
> Changes for v3:
> - Add WARN_ON(state != SYSTEM_FREEING_INITMEM) to fix_kernel_mem_early()
> to make sure that the function used only during permission fixes.
> - Add comment to fix_kernel_mem_early().
>
> Changes for v2:
> - Fix commit message format.
> - Add 'Fixes' tag.
Sweet, thanks.
Ran it through a 32bit build & been running with this applied on 64bit for
the afternoon & everything still seems to be intact. Therefore:
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Thanks for you patch,
Conor.
> ---
> arch/riscv/include/asm/set_memory.h | 20 ++--------
> arch/riscv/kernel/setup.c | 11 -----
> arch/riscv/mm/init.c | 29 +++++++++++---
> arch/riscv/mm/pageattr.c | 62 +++++++++++++++++++++++++----
> 4 files changed, 82 insertions(+), 40 deletions(-)
>
> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
> index a2c14d4b3993..bb0f6b4ed86b 100644
> --- a/arch/riscv/include/asm/set_memory.h
> +++ b/arch/riscv/include/asm/set_memory.h
> @@ -16,28 +16,16 @@ 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_rw_nx(unsigned long addr, int numpages);
> -static __always_inline int set_kernel_memory(char *startp, char *endp,
> - int (*set_memory)(unsigned long start,
> - int num_pages))
> -{
> - unsigned long start = (unsigned long)startp;
> - unsigned long end = (unsigned long)endp;
> - int num_pages = PAGE_ALIGN(end - start) >> PAGE_SHIFT;
> -
> - return set_memory(start, num_pages);
> -}
> +void fix_kernel_mem_early(char *startp, char *endp, pgprot_t set_mask,
> + pgprot_t clear_mask);
> #else
> static inline int set_memory_ro(unsigned long addr, int numpages) { return 0; }
> 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 int set_memory_rw_nx(unsigned long addr, int numpages) { return 0; }
> -static inline int set_kernel_memory(char *startp, char *endp,
> - int (*set_memory)(unsigned long start,
> - int num_pages))
> -{
> - return 0;
> -}
> +static inline void fix_kernel_mem_early(char *startp, char *endp,
> + pgprot_t set_mask, pgprot_t clear_mask) { }
> #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 95ef6e2bf45c..17eae1406092 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -27,7 +27,6 @@
> #include <asm/early_ioremap.h>
> #include <asm/pgtable.h>
> #include <asm/setup.h>
> -#include <asm/set_memory.h>
> #include <asm/sections.h>
> #include <asm/sbi.h>
> #include <asm/tlbflush.h>
> @@ -318,13 +317,3 @@ static int __init topology_init(void)
> return 0;
> }
> subsys_initcall(topology_init);
> -
> -void free_initmem(void)
> -{
> - if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
> - set_kernel_memory(lm_alias(__init_begin), lm_alias(__init_end),
> - IS_ENABLED(CONFIG_64BIT) ?
> - set_memory_rw : set_memory_rw_nx);
> -
> - free_initmem_default(POISON_FREE_INITMEM);
> -}
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index b56a0a75533f..978202712535 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -16,7 +16,6 @@
> #include <linux/of_fdt.h>
> #include <linux/of_reserved_mem.h>
> #include <linux/libfdt.h>
> -#include <linux/set_memory.h>
> #include <linux/dma-map-ops.h>
> #include <linux/crash_dump.h>
> #include <linux/hugetlb.h>
> @@ -28,6 +27,7 @@
> #include <asm/io.h>
> #include <asm/ptdump.h>
> #include <asm/numa.h>
> +#include <asm/set_memory.h>
>
> #include "../kernel/head.h"
>
> @@ -714,10 +714,14 @@ static __init pgprot_t pgprot_from_va(uintptr_t va)
>
> void mark_rodata_ro(void)
> {
> - set_kernel_memory(__start_rodata, _data, set_memory_ro);
> - if (IS_ENABLED(CONFIG_64BIT))
> - set_kernel_memory(lm_alias(__start_rodata), lm_alias(_data),
> - set_memory_ro);
> + pgprot_t set_mask = __pgprot(_PAGE_READ);
> + pgprot_t clear_mask = __pgprot(_PAGE_WRITE);
> +
> + fix_kernel_mem_early(__start_rodata, _data, set_mask, clear_mask);
> + if (IS_ENABLED(CONFIG_64BIT)) {
> + fix_kernel_mem_early(lm_alias(__start_rodata), lm_alias(_data),
> + set_mask, clear_mask);
> + }
>
> debug_checkwx();
> }
> @@ -1243,3 +1247,18 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> return vmemmap_populate_basepages(start, end, node, NULL);
> }
> #endif
> +
> +void free_initmem(void)
> +{
> + pgprot_t set_mask = __pgprot(_PAGE_READ | _PAGE_WRITE);
> + pgprot_t clear_mask = IS_ENABLED(CONFIG_64BIT) ?
> + __pgprot(0) : __pgprot(_PAGE_EXEC);
> +
> + if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
> + fix_kernel_mem_early(lm_alias(__init_begin),
> + lm_alias(__init_end),
> + set_mask, clear_mask);
> + }
> +
> + free_initmem_default(POISON_FREE_INITMEM);
> +}
> diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
> index 5e49e4b4a4cc..74b8107ac743 100644
> --- a/arch/riscv/mm/pageattr.c
> +++ b/arch/riscv/mm/pageattr.c
> @@ -5,6 +5,7 @@
>
> #include <linux/pagewalk.h>
> #include <linux/pgtable.h>
> +#include <linux/sched.h>
> #include <asm/tlbflush.h>
> #include <asm/bitops.h>
> #include <asm/set_memory.h>
> @@ -104,24 +105,69 @@ static const struct mm_walk_ops pageattr_ops = {
> .pte_hole = pageattr_pte_hole,
> };
>
> -static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
> - pgprot_t clear_mask)
> +static int __set_memory_mm(struct mm_struct *mm, unsigned long start,
> + unsigned long end, pgprot_t set_mask,
> + pgprot_t clear_mask)
> {
> int ret;
> - unsigned long start = addr;
> - unsigned long end = start + PAGE_SIZE * numpages;
> struct pageattr_masks masks = {
> .set_mask = set_mask,
> .clear_mask = clear_mask
> };
>
> + mmap_read_lock(mm);
> + ret = walk_page_range_novma(mm, start, end, &pageattr_ops, NULL,
> + &masks);
> + mmap_read_unlock(mm);
> +
> + return ret;
> +}
> +
> +void fix_kernel_mem_early(char *startp, char *endp, pgprot_t set_mask,
> + pgprot_t clear_mask)
> +{
> + struct task_struct *t, *s;
> +
> + unsigned long start = (unsigned long)startp;
> + unsigned long end = PAGE_ALIGN((unsigned long)endp);
> +
> + /*
> + * In the SYSTEM_FREEING_INITMEM state we expect that all async code
> + * is done and no new userspace task can be created.
> + * So rcu_read_lock() should be enough here.
> + */
> + WARN_ON(system_state != SYSTEM_FREEING_INITMEM);
> +
> + __set_memory_mm(current->active_mm, start, end, set_mask, clear_mask);
> + __set_memory_mm(&init_mm, start, end, set_mask, clear_mask);
> +
> + rcu_read_lock();
> + for_each_process(t) {
> + if (t->flags & PF_KTHREAD)
> + continue;
> + for_each_thread(t, s) {
> + if (s->mm) {
> + __set_memory_mm(s->mm, start, end, set_mask,
> + clear_mask);
> + }
> + }
> + }
> + rcu_read_unlock();
> +
> + flush_tlb_kernel_range(start, end);
> +}
> +
> +static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
> + pgprot_t clear_mask)
> +{
> + int ret;
> + unsigned long start = addr;
> + unsigned long end = start + PAGE_SIZE * numpages;
> +
> if (!numpages)
> return 0;
>
> - mmap_read_lock(&init_mm);
> - ret = walk_page_range_novma(&init_mm, start, end, &pageattr_ops, NULL,
> - &masks);
> - mmap_read_unlock(&init_mm);
> + ret = __set_memory_mm(&init_mm, start, end, set_mask, clear_mask);
>
> flush_tlb_kernel_range(start, end);
>
> --
> 2.37.2
>
>
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