| Message ID | 20170326210825.23255-2-ewk@edkovsky.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
+++ Eddie Kovsky [26/03/17 15:08 -0600]: >Implement a mechanism to check if a module's address is in >the rodata or ro_after_init sections. It mimics the existing functions >that test if an address is inside a module's text section. > >Functions that take a module as an argument will be able to verify that the >module address is in a read-only section. The idea is to prevent structures >(including modules) that are not read-only from being passed to functions. > >This implements the first half of a suggestion made by Kees Cook for >the Kernel Self Protection Project: > > - provide mechanism to check for ro_after_init memory areas, and > reject structures not marked ro_after_init in vmbus_register() > >Suggested-by: Kees Cook <keescook@chromium.org> >Signed-off-by: Eddie Kovsky <ewk@edkovsky.org> Thanks for the respin, this looks much better. Acked-by: Jessica Yu <jeyu@redhat.com> >--- >Changes in v4: > - Rename function __module_ro_address() to __module_rodata_address() > - Move module_rodata_address() stub below is_module_address() > - Minor comment fixes > - Verify that mod is not NULL before setting up layout variables >Changes in v3: > - Change function name is_module_ro_address() to >is_module_rodata_address(). > - Improve comments on is_module_rodata_address(). > - Add a !CONFIG_MODULES stub for is_module_rodata_address. > - Correct and simplify the check for the read-only memory regions in >the module address. >--- > include/linux/module.h | 12 ++++++++++++ > kernel/module.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 65 insertions(+) > >diff --git a/include/linux/module.h b/include/linux/module.h >index 9ad68561d8c2..a3d17b081de3 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_rodata_address(unsigned long addr); > bool is_module_address(unsigned long addr); >+bool is_module_rodata_address(unsigned long addr); > bool __is_module_percpu_address(unsigned long addr, unsigned long *can_addr); > bool is_module_percpu_address(unsigned long addr); > bool is_module_text_address(unsigned long addr); >@@ -646,6 +648,11 @@ static inline struct module *__module_address(unsigned long addr) > return NULL; > } > >+static inline struct module *__module_rodata_address(unsigned long addr) >+{ >+ return NULL; >+} >+ > static inline struct module *__module_text_address(unsigned long addr) > { > return NULL; >@@ -656,6 +663,11 @@ static inline bool is_module_address(unsigned long addr) > return false; > } > >+static inline bool is_module_rodata_address(unsigned long addr) >+{ >+ return false; >+} >+ > static inline bool is_module_percpu_address(unsigned long addr) > { > return false; >diff --git a/kernel/module.c b/kernel/module.c >index 8ffcd29a4245..26bd62c61d87 100644 >--- a/kernel/module.c >+++ b/kernel/module.c >@@ -4292,6 +4292,59 @@ struct module *__module_text_address(unsigned long addr) > } > EXPORT_SYMBOL_GPL(__module_text_address); > >+/** >+ * is_module_rodata_address - is this address inside read-only module data? >+ * @addr: the address to check. >+ * >+ */ >+bool is_module_rodata_address(unsigned long addr) >+{ >+ bool ret; >+ >+ preempt_disable(); >+ ret = __module_rodata_address(addr) != NULL; >+ preempt_enable(); >+ >+ return ret; >+} >+ >+/* >+ * __module_rodata_address - get the module whose rodata/ro_after_init sections >+ * contain the given 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_rodata_address(unsigned long addr) >+{ >+ struct module *mod = __module_address(addr); >+ >+ /* >+ * Make sure module is within the read-only section. >+ * range(base + text_size, base + ro_after_init_size) >+ * encompasses both the rodata and ro_after_init regions. >+ * See comment above frob_text() for the layout diagram. >+ */ >+ if (mod) { >+ void *init_base = mod->init_layout.base; >+ unsigned int init_text_size = mod->init_layout.text_size; >+ unsigned int init_ro_after_init_size = mod->init_layout.ro_after_init_size; >+ >+ void *core_base = mod->core_layout.base; >+ unsigned int core_text_size = mod->core_layout.text_size; >+ unsigned int core_ro_after_init_size = mod->core_layout.ro_after_init_size; >+ >+ if (!within(addr, init_base + init_text_size, >+ init_ro_after_init_size - init_text_size) >+ && !within(addr, core_base + core_text_size, >+ core_ro_after_init_size - core_text_size)) >+ mod = NULL; >+ } >+ return mod; >+} >+EXPORT_SYMBOL_GPL(__module_rodata_address); >+ > /* Don't grab lock, we're oopsing. */ > void print_modules(void) > { >-- >2.12.1 >
diff --git a/include/linux/module.h b/include/linux/module.h index 9ad68561d8c2..a3d17b081de3 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_rodata_address(unsigned long addr); bool is_module_address(unsigned long addr); +bool is_module_rodata_address(unsigned long addr); bool __is_module_percpu_address(unsigned long addr, unsigned long *can_addr); bool is_module_percpu_address(unsigned long addr); bool is_module_text_address(unsigned long addr); @@ -646,6 +648,11 @@ static inline struct module *__module_address(unsigned long addr) return NULL; } +static inline struct module *__module_rodata_address(unsigned long addr) +{ + return NULL; +} + static inline struct module *__module_text_address(unsigned long addr) { return NULL; @@ -656,6 +663,11 @@ static inline bool is_module_address(unsigned long addr) return false; } +static inline bool is_module_rodata_address(unsigned long addr) +{ + return false; +} + static inline bool is_module_percpu_address(unsigned long addr) { return false; diff --git a/kernel/module.c b/kernel/module.c index 8ffcd29a4245..26bd62c61d87 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -4292,6 +4292,59 @@ struct module *__module_text_address(unsigned long addr) } EXPORT_SYMBOL_GPL(__module_text_address); +/** + * is_module_rodata_address - is this address inside read-only module data? + * @addr: the address to check. + * + */ +bool is_module_rodata_address(unsigned long addr) +{ + bool ret; + + preempt_disable(); + ret = __module_rodata_address(addr) != NULL; + preempt_enable(); + + return ret; +} + +/* + * __module_rodata_address - get the module whose rodata/ro_after_init sections + * contain the given 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_rodata_address(unsigned long addr) +{ + struct module *mod = __module_address(addr); + + /* + * Make sure module is within the read-only section. + * range(base + text_size, base + ro_after_init_size) + * encompasses both the rodata and ro_after_init regions. + * See comment above frob_text() for the layout diagram. + */ + if (mod) { + void *init_base = mod->init_layout.base; + unsigned int init_text_size = mod->init_layout.text_size; + unsigned int init_ro_after_init_size = mod->init_layout.ro_after_init_size; + + void *core_base = mod->core_layout.base; + unsigned int core_text_size = mod->core_layout.text_size; + unsigned int core_ro_after_init_size = mod->core_layout.ro_after_init_size; + + if (!within(addr, init_base + init_text_size, + init_ro_after_init_size - init_text_size) + && !within(addr, core_base + core_text_size, + core_ro_after_init_size - core_text_size)) + mod = NULL; + } + return mod; +} +EXPORT_SYMBOL_GPL(__module_rodata_address); + /* Don't grab lock, we're oopsing. */ void print_modules(void) {
Implement a mechanism to check if a module's address is in the rodata or ro_after_init sections. It mimics the existing functions that test if an address is inside a module's text section. Functions that take a module as an argument will be able to verify that the module address is in a read-only section. The idea is to prevent structures (including modules) that are not read-only from being passed to functions. This implements the first half of a suggestion made by Kees Cook for the Kernel Self Protection Project: - provide mechanism to check for ro_after_init memory areas, and reject structures not marked ro_after_init in vmbus_register() Suggested-by: Kees Cook <keescook@chromium.org> Signed-off-by: Eddie Kovsky <ewk@edkovsky.org> --- Changes in v4: - Rename function __module_ro_address() to __module_rodata_address() - Move module_rodata_address() stub below is_module_address() - Minor comment fixes - Verify that mod is not NULL before setting up layout variables Changes in v3: - Change function name is_module_ro_address() to is_module_rodata_address(). - Improve comments on is_module_rodata_address(). - Add a !CONFIG_MODULES stub for is_module_rodata_address. - Correct and simplify the check for the read-only memory regions in the module address. --- include/linux/module.h | 12 ++++++++++++ kernel/module.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 65 insertions(+)