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    Subject[PATCH v10 06/14] module: Move strict rwx support to a separate file
    Date
    No functional change.

    This patch migrates code that makes module text
    and rodata memory read-only and non-text memory
    non-executable from core module code into
    kernel/module/strict_rwx.c.

    Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
    Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
    ---
    kernel/module/Makefile | 1 +
    kernel/module/internal.h | 32 ++++++++++++
    kernel/module/main.c | 99 +-------------------------------------
    kernel/module/strict_rwx.c | 85 ++++++++++++++++++++++++++++++++
    4 files changed, 120 insertions(+), 97 deletions(-)
    create mode 100644 kernel/module/strict_rwx.c

    diff --git a/kernel/module/Makefile b/kernel/module/Makefile
    index 88774e386276..d313c8472cb3 100644
    --- a/kernel/module/Makefile
    +++ b/kernel/module/Makefile
    @@ -12,3 +12,4 @@ obj-$(CONFIG_MODULE_DECOMPRESS) += decompress.o
    obj-$(CONFIG_MODULE_SIG) += signing.o
    obj-$(CONFIG_LIVEPATCH) += livepatch.o
    obj-$(CONFIG_MODULES_TREE_LOOKUP) += tree_lookup.o
    +obj-$(CONFIG_STRICT_MODULE_RWX) += strict_rwx.o
    diff --git a/kernel/module/internal.h b/kernel/module/internal.h
    index f1682e3677be..a6895bb5598a 100644
    --- a/kernel/module/internal.h
    +++ b/kernel/module/internal.h
    @@ -20,6 +20,17 @@
    /* Maximum number of characters written by module_flags() */
    #define MODULE_FLAGS_BUF_SIZE (TAINT_FLAGS_COUNT + 4)

    +/*
    + * Modules' sections will be aligned on page boundaries
    + * to ensure complete separation of code and data, but
    + * only when CONFIG_ARCH_HAS_STRICT_MODULE_RWX=y
    + */
    +#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
    +# define debug_align(X) PAGE_ALIGN(X)
    +#else
    +# define debug_align(X) (X)
    +#endif
    +
    extern struct mutex module_mutex;
    extern struct list_head modules;

    @@ -126,3 +137,24 @@ static inline struct module *mod_find(unsigned long addr)
    return NULL;
    }
    #endif /* CONFIG_MODULES_TREE_LOOKUP */
    +
    +#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
    +void frob_text(const struct module_layout *layout, int (*set_memory)(unsigned long start,
    + int num_pages));
    +#endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */
    +
    +#ifdef CONFIG_STRICT_MODULE_RWX
    +void module_enable_ro(const struct module *mod, bool after_init);
    +void module_enable_nx(const struct module *mod);
    +int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
    + char *secstrings, struct module *mod);
    +
    +#else /* !CONFIG_STRICT_MODULE_RWX */
    +static inline void module_enable_nx(const struct module *mod) { }
    +static inline void module_enable_ro(const struct module *mod, bool after_init) {}
    +static inline int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
    + char *secstrings, struct module *mod)
    +{
    + return 0;
    +}
    +#endif /* CONFIG_STRICT_MODULE_RWX */
    diff --git a/kernel/module/main.c b/kernel/module/main.c
    index 76b53880ad91..5cd63f14b1ef 100644
    --- a/kernel/module/main.c
    +++ b/kernel/module/main.c
    @@ -63,17 +63,6 @@
    #define CREATE_TRACE_POINTS
    #include <trace/events/module.h>

    -/*
    - * Modules' sections will be aligned on page boundaries
    - * to ensure complete separation of code and data, but
    - * only when CONFIG_ARCH_HAS_STRICT_MODULE_RWX=y
    - */
    -#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
    -# define debug_align(X) ALIGN(X, PAGE_SIZE)
    -#else
    -# define debug_align(X) (X)
    -#endif
    -
    /*
    * Mutex protects:
    * 1) List of modules (also safely readable with preempt_disable),
    @@ -1819,8 +1808,8 @@ static void mod_sysfs_teardown(struct module *mod)
    * whether we are strict.
    */
    #ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
    -static void frob_text(const struct module_layout *layout,
    - int (*set_memory)(unsigned long start, int num_pages))
    +void frob_text(const struct module_layout *layout,
    + int (*set_memory)(unsigned long start, int num_pages))
    {
    BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
    BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
    @@ -1837,90 +1826,6 @@ static void module_enable_x(const struct module *mod)
    static void module_enable_x(const struct module *mod) { }
    #endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */

    -#ifdef CONFIG_STRICT_MODULE_RWX
    -static void frob_rodata(const struct module_layout *layout,
    - int (*set_memory)(unsigned long start, int num_pages))
    -{
    - BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
    - BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
    - BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
    - set_memory((unsigned long)layout->base + layout->text_size,
    - (layout->ro_size - layout->text_size) >> PAGE_SHIFT);
    -}
    -
    -static void frob_ro_after_init(const struct module_layout *layout,
    - int (*set_memory)(unsigned long start, int num_pages))
    -{
    - BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
    - BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
    - BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
    - set_memory((unsigned long)layout->base + layout->ro_size,
    - (layout->ro_after_init_size - layout->ro_size) >> PAGE_SHIFT);
    -}
    -
    -static void frob_writable_data(const struct module_layout *layout,
    - int (*set_memory)(unsigned long start, int num_pages))
    -{
    - BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
    - BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
    - BUG_ON((unsigned long)layout->size & (PAGE_SIZE-1));
    - set_memory((unsigned long)layout->base + layout->ro_after_init_size,
    - (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);
    -}
    -
    -static void module_enable_ro(const struct module *mod, bool after_init)
    -{
    - if (!rodata_enabled)
    - return;
    -
    - set_vm_flush_reset_perms(mod->core_layout.base);
    - set_vm_flush_reset_perms(mod->init_layout.base);
    - frob_text(&mod->core_layout, set_memory_ro);
    -
    - frob_rodata(&mod->core_layout, set_memory_ro);
    - frob_text(&mod->init_layout, set_memory_ro);
    - frob_rodata(&mod->init_layout, set_memory_ro);
    -
    - if (after_init)
    - frob_ro_after_init(&mod->core_layout, set_memory_ro);
    -}
    -
    -static void module_enable_nx(const struct module *mod)
    -{
    - frob_rodata(&mod->core_layout, set_memory_nx);
    - frob_ro_after_init(&mod->core_layout, set_memory_nx);
    - frob_writable_data(&mod->core_layout, set_memory_nx);
    - frob_rodata(&mod->init_layout, set_memory_nx);
    - frob_writable_data(&mod->init_layout, set_memory_nx);
    -}
    -
    -static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
    - char *secstrings, struct module *mod)
    -{
    - const unsigned long shf_wx = SHF_WRITE|SHF_EXECINSTR;
    - int i;
    -
    - for (i = 0; i < hdr->e_shnum; i++) {
    - if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
    - pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
    - mod->name, secstrings + sechdrs[i].sh_name, i);
    - return -ENOEXEC;
    - }
    - }
    -
    - return 0;
    -}
    -
    -#else /* !CONFIG_STRICT_MODULE_RWX */
    -static void module_enable_nx(const struct module *mod) { }
    -static void module_enable_ro(const struct module *mod, bool after_init) {}
    -static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
    - char *secstrings, struct module *mod)
    -{
    - return 0;
    -}
    -#endif /* CONFIG_STRICT_MODULE_RWX */
    -
    void __weak module_memfree(void *module_region)
    {
    /*
    diff --git a/kernel/module/strict_rwx.c b/kernel/module/strict_rwx.c
    new file mode 100644
    index 000000000000..7949dfd449c2
    --- /dev/null
    +++ b/kernel/module/strict_rwx.c
    @@ -0,0 +1,85 @@
    +// SPDX-License-Identifier: GPL-2.0-or-later
    +/*
    + * Module strict rwx
    + *
    + * Copyright (C) 2015 Rusty Russell
    + */
    +
    +#include <linux/module.h>
    +#include <linux/mm.h>
    +#include <linux/vmalloc.h>
    +#include <linux/set_memory.h>
    +#include "internal.h"
    +
    +static void frob_rodata(const struct module_layout *layout,
    + int (*set_memory)(unsigned long start, int num_pages))
    +{
    + BUG_ON(!PAGE_ALIGNED(layout->base));
    + BUG_ON(!PAGE_ALIGNED(layout->text_size));
    + BUG_ON(!PAGE_ALIGNED(layout->ro_size));
    + set_memory((unsigned long)layout->base + layout->text_size,
    + (layout->ro_size - layout->text_size) >> PAGE_SHIFT);
    +}
    +
    +static void frob_ro_after_init(const struct module_layout *layout,
    + int (*set_memory)(unsigned long start, int num_pages))
    +{
    + BUG_ON(!PAGE_ALIGNED(layout->base));
    + BUG_ON(!PAGE_ALIGNED(layout->ro_size));
    + BUG_ON(!PAGE_ALIGNED(layout->ro_after_init_size));
    + set_memory((unsigned long)layout->base + layout->ro_size,
    + (layout->ro_after_init_size - layout->ro_size) >> PAGE_SHIFT);
    +}
    +
    +static void frob_writable_data(const struct module_layout *layout,
    + int (*set_memory)(unsigned long start, int num_pages))
    +{
    + BUG_ON(!PAGE_ALIGNED(layout->base));
    + BUG_ON(!PAGE_ALIGNED(layout->ro_after_init_size));
    + BUG_ON(!PAGE_ALIGNED(layout->size));
    + set_memory((unsigned long)layout->base + layout->ro_after_init_size,
    + (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);
    +}
    +
    +void module_enable_ro(const struct module *mod, bool after_init)
    +{
    + if (!rodata_enabled)
    + return;
    +
    + set_vm_flush_reset_perms(mod->core_layout.base);
    + set_vm_flush_reset_perms(mod->init_layout.base);
    + frob_text(&mod->core_layout, set_memory_ro);
    +
    + frob_rodata(&mod->core_layout, set_memory_ro);
    + frob_text(&mod->init_layout, set_memory_ro);
    + frob_rodata(&mod->init_layout, set_memory_ro);
    +
    + if (after_init)
    + frob_ro_after_init(&mod->core_layout, set_memory_ro);
    +}
    +
    +void module_enable_nx(const struct module *mod)
    +{
    + frob_rodata(&mod->core_layout, set_memory_nx);
    + frob_ro_after_init(&mod->core_layout, set_memory_nx);
    + frob_writable_data(&mod->core_layout, set_memory_nx);
    + frob_rodata(&mod->init_layout, set_memory_nx);
    + frob_writable_data(&mod->init_layout, set_memory_nx);
    +}
    +
    +int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
    + char *secstrings, struct module *mod)
    +{
    + const unsigned long shf_wx = SHF_WRITE | SHF_EXECINSTR;
    + int i;
    +
    + for (i = 0; i < hdr->e_shnum; i++) {
    + if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
    + pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
    + mod->name, secstrings + sechdrs[i].sh_name, i);
    + return -ENOEXEC;
    + }
    + }
    +
    + return 0;
    +}
    --
    2.34.1
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