module: add flags arg to sys_finit_module()

Thanks to Michael Kerrisk for keeping us honest. These flags are actually useful for eliminating the only case where kmod has to mangle a module's internals: for overriding module versioning. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Lucas De Marchi <lucas.demarchi@profusion.mobi> Acked-by: Kees Cook <keescook@chromium.org>

module: add flags arg to sys_finit_module()
Thanks to Michael Kerrisk for keeping us honest. These flags are actually useful for eliminating the only case where kmod has to mangle a module's internals: for overriding module versioning. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Lucas De Marchi <lucas.demarchi@profusion.mobi> Acked-by: Kees Cook <keescook@chromium.org>
Rusty Russell
1 parent 34e1169d99
Showing 3 changed files with 35 additions and 15 deletions Side-by-side Diff
include/linux/syscalls.h
include/uapi/linux/module.h
kernel/module.c
@@ -868,6 +868,6 @@
  
 asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
 			 unsigned long idx1, unsigned long idx2);
-asmlinkage long sys_finit_module(int fd, const char __user *uargs);
+asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
 #endif
+#ifndef _UAPI_LINUX_MODULE_H
+#define _UAPI_LINUX_MODULE_H
+
+/* Flags for sys_finit_module: */
+#define MODULE_INIT_IGNORE_MODVERSIONS	1
+#define MODULE_INIT_IGNORE_VERMAGIC	2
+
+#endif /* _UAPI_LINUX_MODULE_H */
@@ -60,6 +60,7 @@
 #include <linux/pfn.h>
 #include <linux/bsearch.h>
 #include <linux/fips.h>
+#include <uapi/linux/module.h>
 #include "module-internal.h"
  
 #define CREATE_TRACE_POINTS
@@ -2553,7 +2554,7 @@
 	vfree(info->hdr);
 }
  
-static int rewrite_section_headers(struct load_info *info)
+static int rewrite_section_headers(struct load_info *info, int flags)
 {
 	unsigned int i;
  
@@ -2581,7 +2582,10 @@
 	}
  
 	/* Track but don't keep modinfo and version sections. */
-	info->index.vers = find_sec(info, "__versions");
+	if (flags & MODULE_INIT_IGNORE_MODVERSIONS)
+		info->index.vers = 0; /* Pretend no __versions section! */
+	else
+		info->index.vers = find_sec(info, "__versions");
 	info->index.info = find_sec(info, ".modinfo");
 	info->sechdrs[info->index.info].sh_flags &= ~(unsigned long)SHF_ALLOC;
 	info->sechdrs[info->index.vers].sh_flags &= ~(unsigned long)SHF_ALLOC;
@@ -2596,7 +2600,7 @@
  * Return the temporary module pointer (we'll replace it with the final
  * one when we move the module sections around).
  */
-static struct module *setup_load_info(struct load_info *info)
+static struct module *setup_load_info(struct load_info *info, int flags)
 {
 	unsigned int i;
 	int err;
@@ -2607,7 +2611,7 @@
 	info->secstrings = (void *)info->hdr
 		+ info->sechdrs[info->hdr->e_shstrndx].sh_offset;
  
-	err = rewrite_section_headers(info);
+	err = rewrite_section_headers(info, flags);
 	if (err)
 		return ERR_PTR(err);
  
  
@@ -2645,11 +2649,14 @@
 	return mod;
 }
  
-static int check_modinfo(struct module *mod, struct load_info *info)
+static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 {
 	const char *modmagic = get_modinfo(info, "vermagic");
 	int err;
  
+	if (flags & MODULE_INIT_IGNORE_VERMAGIC)
+		modmagic = NULL;
+
 	/* This is allowed: modprobe --force will invalidate it. */
 	if (!modmagic) {
 		err = try_to_force_load(mod, "bad vermagic");
  
  
@@ -2885,18 +2892,18 @@
 	return 0;
 }
  
-static struct module *layout_and_allocate(struct load_info *info)
+static struct module *layout_and_allocate(struct load_info *info, int flags)
 {
 	/* Module within temporary copy. */
 	struct module *mod;
 	Elf_Shdr *pcpusec;
 	int err;
  
-	mod = setup_load_info(info);
+	mod = setup_load_info(info, flags);
 	if (IS_ERR(mod))
 		return mod;
  
-	err = check_modinfo(mod, info);
+	err = check_modinfo(mod, info, flags);
 	if (err)
 		return ERR_PTR(err);
  
@@ -3078,7 +3085,8 @@
  
 /* Allocate and load the module: note that size of section 0 is always
    zero, and we rely on this for optional sections. */
-static int load_module(struct load_info *info, const char __user *uargs)
+static int load_module(struct load_info *info, const char __user *uargs,
+		       int flags)
 {
 	struct module *mod, *old;
 	long err;
@@ -3092,7 +3100,7 @@
 		goto free_copy;
  
 	/* Figure out module layout, and allocate all the memory. */
-	mod = layout_and_allocate(info);
+	mod = layout_and_allocate(info, flags);
 	if (IS_ERR(mod)) {
 		err = PTR_ERR(mod);
 		goto free_copy;
  
@@ -3241,10 +3249,10 @@
 	if (err)
 		return err;
  
-	return load_module(&info, uargs);
+	return load_module(&info, uargs, 0);
 }
  
-SYSCALL_DEFINE2(finit_module, int, fd, const char __user *, uargs)
+SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
 {
 	int err;
 	struct load_info info = { };
  
  
@@ -3253,13 +3261,17 @@
 	if (err)
 		return err;
  
-	pr_debug("finit_module: fd=%d, uargs=%p\n", fd, uargs);
+	pr_debug("finit_module: fd=%d, uargs=%p, flags=%i\n", fd, uargs, flags);
  
+	if (flags & ~(MODULE_INIT_IGNORE_MODVERSIONS
+		      |MODULE_INIT_IGNORE_VERMAGIC))
+		return -EINVAL;
+
 	err = copy_module_from_fd(fd, &info);
 	if (err)
 		return err;
  
-	return load_module(&info, uargs);
+	return load_module(&info, uargs, flags);
 }
  
 static inline int within(unsigned long addr, void *start, unsigned long size)
...	...	@@ -868,6 +868,6 @@
868	868
869	869	asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
870	870	unsigned long idx1, unsigned long idx2);
871		-asmlinkage long sys_finit_module(int fd, const char __user *uargs);
	871	+asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
872	872	#endif
	1	+#ifndef _UAPI_LINUX_MODULE_H
	2	+#define _UAPI_LINUX_MODULE_H
	3	+
	4	+/* Flags for sys_finit_module: */
	5	+#define MODULE_INIT_IGNORE_MODVERSIONS 1
	6	+#define MODULE_INIT_IGNORE_VERMAGIC 2
	7	+
	8	+#endif /* _UAPI_LINUX_MODULE_H */
...	...	@@ -60,6 +60,7 @@
60	60	#include <linux/pfn.h>
61	61	#include <linux/bsearch.h>
62	62	#include <linux/fips.h>
	63	+#include <uapi/linux/module.h>
63	64	#include "module-internal.h"
64	65
65	66	#define CREATE_TRACE_POINTS
...	...	@@ -2553,7 +2554,7 @@
2553	2554	vfree(info->hdr);
2554	2555	}
2555	2556
2556		-static int rewrite_section_headers(struct load_info *info)
	2557	+static int rewrite_section_headers(struct load_info *info, int flags)
2557	2558	{
2558	2559	unsigned int i;
2559	2560
...	...	@@ -2581,7 +2582,10 @@
2581	2582	}
2582	2583
2583	2584	/* Track but don't keep modinfo and version sections. */
2584		- info->index.vers = find_sec(info, "__versions");
	2585	+ if (flags & MODULE_INIT_IGNORE_MODVERSIONS)
	2586	+ info->index.vers = 0; /* Pretend no __versions section! */
	2587	+ else
	2588	+ info->index.vers = find_sec(info, "__versions");
2585	2589	info->index.info = find_sec(info, ".modinfo");
2586	2590	info->sechdrs[info->index.info].sh_flags &= ~(unsigned long)SHF_ALLOC;
2587	2591	info->sechdrs[info->index.vers].sh_flags &= ~(unsigned long)SHF_ALLOC;
...	...	@@ -2596,7 +2600,7 @@
2596	2600	* Return the temporary module pointer (we'll replace it with the final
2597	2601	* one when we move the module sections around).
2598	2602	*/
2599		-static struct module setup_load_info(struct load_info info)
	2603	+static struct module setup_load_info(struct load_info info, int flags)
2600	2604	{
2601	2605	unsigned int i;
2602	2606	int err;
...	...	@@ -2607,7 +2611,7 @@
2607	2611	info->secstrings = (void *)info->hdr
2608	2612	+ info->sechdrs[info->hdr->e_shstrndx].sh_offset;
2609	2613
2610		- err = rewrite_section_headers(info);
	2614	+ err = rewrite_section_headers(info, flags);
2611	2615	if (err)
2612	2616	return ERR_PTR(err);
2613	2617
2614	2618
...	...	@@ -2645,11 +2649,14 @@
2645	2649	return mod;
2646	2650	}
2647	2651
2648		-static int check_modinfo(struct module mod, struct load_info info)
	2652	+static int check_modinfo(struct module mod, struct load_info info, int flags)
2649	2653	{
2650	2654	const char *modmagic = get_modinfo(info, "vermagic");
2651	2655	int err;
2652	2656
	2657	+ if (flags & MODULE_INIT_IGNORE_VERMAGIC)
	2658	+ modmagic = NULL;
	2659	+
2653	2660	/* This is allowed: modprobe --force will invalidate it. */
2654	2661	if (!modmagic) {
2655	2662	err = try_to_force_load(mod, "bad vermagic");
2656	2663
2657	2664
...	...	@@ -2885,18 +2892,18 @@
2885	2892	return 0;
2886	2893	}
2887	2894
2888		-static struct module layout_and_allocate(struct load_info info)
	2895	+static struct module layout_and_allocate(struct load_info info, int flags)
2889	2896	{
2890	2897	/* Module within temporary copy. */
2891	2898	struct module *mod;
2892	2899	Elf_Shdr *pcpusec;
2893	2900	int err;
2894	2901
2895		- mod = setup_load_info(info);
	2902	+ mod = setup_load_info(info, flags);
2896	2903	if (IS_ERR(mod))
2897	2904	return mod;
2898	2905
2899		- err = check_modinfo(mod, info);
	2906	+ err = check_modinfo(mod, info, flags);
2900	2907	if (err)
2901	2908	return ERR_PTR(err);
2902	2909
...	...	@@ -3078,7 +3085,8 @@
3078	3085
3079	3086	/* Allocate and load the module: note that size of section 0 is always
3080	3087	zero, and we rely on this for optional sections. */
3081		-static int load_module(struct load_info info, const char __user uargs)
	3088	+static int load_module(struct load_info info, const char __user uargs,
	3089	+ int flags)
3082	3090	{
3083	3091	struct module mod, old;
3084	3092	long err;
...	...	@@ -3092,7 +3100,7 @@
3092	3100	goto free_copy;
3093	3101
3094	3102	/* Figure out module layout, and allocate all the memory. */
3095		- mod = layout_and_allocate(info);
	3103	+ mod = layout_and_allocate(info, flags);
3096	3104	if (IS_ERR(mod)) {
3097	3105	err = PTR_ERR(mod);
3098	3106	goto free_copy;
3099	3107
...	...	@@ -3241,10 +3249,10 @@
3241	3249	if (err)
3242	3250	return err;
3243	3251
3244		- return load_module(&info, uargs);
	3252	+ return load_module(&info, uargs, 0);
3245	3253	}
3246	3254
3247		-SYSCALL_DEFINE2(finit_module, int, fd, const char __user *, uargs)
	3255	+SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
3248	3256	{
3249	3257	int err;
3250	3258	struct load_info info = { };
3251	3259
3252	3260
...	...	@@ -3253,13 +3261,17 @@
3253	3261	if (err)
3254	3262	return err;
3255	3263
3256		- pr_debug("finit_module: fd=%d, uargs=%p\n", fd, uargs);
	3264	+ pr_debug("finit_module: fd=%d, uargs=%p, flags=%i\n", fd, uargs, flags);
3257	3265
	3266	+ if (flags & ~(MODULE_INIT_IGNORE_MODVERSIONS
	3267	+ \|MODULE_INIT_IGNORE_VERMAGIC))
	3268	+ return -EINVAL;
	3269	+
3258	3270	err = copy_module_from_fd(fd, &info);
3259	3271	if (err)
3260	3272	return err;
3261	3273
3262		- return load_module(&info, uargs);
	3274	+ return load_module(&info, uargs, flags);
3263	3275	}
3264	3276
3265	3277	static inline int within(unsigned long addr, void *start, unsigned long size)