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    Subject[PATCH v2 1/3] module: verify address is read-only
    Date
    Implement a mechanism to check if a module's address is in
    the rodata or ro_after_init sections. It mimics the exsiting functions
    that test if an address is inside a module's text section.

    Signed-off-by: Eddie Kovsky <ewk@edkovsky.org>
    ---
    include/linux/module.h | 7 +++++++
    kernel/module.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 51 insertions(+)

    diff --git a/include/linux/module.h b/include/linux/module.h
    index 0297c5cd7cdf..1608d3570ee2 100644
    --- a/include/linux/module.h
    +++ b/include/linux/module.h
    @@ -492,7 +492,9 @@ static inline int module_is_live(struct module *mod)

    struct module *__module_text_address(unsigned long addr);
    struct module *__module_address(unsigned long addr);
    +struct module *__module_ro_address(unsigned long addr);
    bool is_module_address(unsigned long addr);
    +bool is_module_ro_address(unsigned long addr);
    bool is_module_percpu_address(unsigned long addr);
    bool is_module_text_address(unsigned long addr);

    @@ -645,6 +647,11 @@ static inline struct module *__module_address(unsigned long addr)
    return NULL;
    }

    +static inline struct module *__module_ro_address(unsigned long addr)
    +{
    + return NULL;
    +}
    +
    static inline struct module *__module_text_address(unsigned long addr)
    {
    return NULL;
    diff --git a/kernel/module.c b/kernel/module.c
    index 7eba6dea4f41..298cfe4645b1 100644
    --- a/kernel/module.c
    +++ b/kernel/module.c
    @@ -4275,6 +4275,50 @@ struct module *__module_text_address(unsigned long addr)
    }
    EXPORT_SYMBOL_GPL(__module_text_address);

    +/**
    + * is_module_text_ro_address - is this address inside read-only module code?
    + * @addr: the address to check.
    + *
    + */
    +bool is_module_ro_address(unsigned long addr)
    +{
    + bool ret;
    +
    + preempt_disable();
    + ret = __module_ro_address(addr) != NULL;
    + preempt_enable();
    +
    + return ret;
    +}
    +
    +/*
    + * __module_ro_address - get the module whose code contains a read-only address.
    + * @addr: the address.
    + *
    + * Must be called with preempt disabled or module mutex held so that
    + * module doesn't get freed during this.
    + */
    +struct module *__module_ro_address(unsigned long addr)
    +{
    + struct module *mod = __module_address(addr);
    +
    + if (mod) {
    + /* Make sure it's within the read-only section. */
    + if (!within(addr, mod->init_layout.base,
    + mod->init_layout.ro_size)
    + && !within(addr, mod->core_layout.base,
    + mod->core_layout.ro_size))
    + mod = NULL;
    + if (!within(addr, mod->init_layout.base,
    + mod->init_layout.ro_after_init_size)
    + && !within(addr, mod->core_layout.base,
    + mod->core_layout.ro_after_init_size))
    + mod = NULL;
    + }
    + return mod;
    +}
    +EXPORT_SYMBOL_GPL(__module_ro_address);
    +
    /* Don't grab lock, we're oopsing. */
    void print_modules(void)
    {
    --
    2.11.1
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