Re: [PATCH 1/4] module: add syscall to load module from fd

Signed-off-by: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 32bc035..8cf7b50 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h

@@ -868,5 +868,5 @@ asmlinkage long sys_process_vm_writev(pid_t pid,

 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

diff --git a/include/uapi/linux/module.h b/include/uapi/linux/module.h
new file mode 100644
index 0000000..38da425
--- /dev/null
+++ b/include/uapi/linux/module.h

@@ -0,0 +1,8 @@
+#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 */

diff --git a/kernel/module.c b/kernel/module.c
index 261bf82..55b49cd 100644
--- a/kernel/module.c
+++ b/kernel/module.c

@@ -61,6 +61,7 @@
 #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

@@ -2569,7 +2570,7 @@ static void free_copy(struct load_info *info)
        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;

@@ -2597,7 +2598,10 @@ static int rewrite_section_headers(struct load_info *info)
        }

        /* 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;

@@ -2612,7 +2617,7 @@ static int rewrite_section_headers(struct load_info *info)
  * 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;

@@ -2623,7 +2628,7 @@ static struct module *setup_load_info(struct load_info *info)
        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);

@@ -2661,11 +2666,14 @@ static struct module *setup_load_info(struct load_info *info)
        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");

@@ -2901,18 +2909,18 @@ int __weak module_frob_arch_sections(Elf_Ehdr *hdr,
        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);

@@ -3094,7 +3102,8 @@ static int may_init_module(void)

 /* 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;

@@ -3108,7 +3117,7 @@ static int load_module(struct load_info *info, const char __user *uargs)
                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;

@@ -3257,10 +3269,10 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
        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 = { };

@@ -3269,13 +3281,17 @@ SYSCALL_DEFINE2(finit_module, int, fd, const char __user *, uargs)
        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)
--

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