From 3a45b87ac36f60962d6d19c592813e186a9e82e6 Mon Sep 17 00:00:00 2001 From: Mike Frysinger Date: Thu, 15 Sep 2016 12:16:33 +0200 Subject: [PATCH] modutils: support finit_module syscall On some systems like Chromium OS, loading modules from non-verified filesystems is denied. Only finit_module is allowed because an open fd is passed which can be checked against a verified location. Change the module loading code to first attempt finit_module and if that fails for whatever reason, fall back to the existing logic. On x86_64, this adds ~80 bytes to modutils/modutils.o and ~68 bytes to modutils/modprobe-small.o. Signed-off-by: Mike Frysinger Signed-off-by: Denys Vlasenko --- modutils/modprobe-small.c | 33 ++++++++++++++++++++++++++++++--- modutils/modutils.c | 21 +++++++++++++++++++++ 2 files changed, 51 insertions(+), 3 deletions(-) diff --git a/modutils/modprobe-small.c b/modutils/modprobe-small.c index 5936e48cf..a47e52234 100644 --- a/modutils/modprobe-small.c +++ b/modutils/modprobe-small.c @@ -18,9 +18,13 @@ /* After libbb.h, since it needs sys/types.h on some systems */ #include /* uname() */ #include +#include extern int init_module(void *module, unsigned long len, const char *options); extern int delete_module(const char *module, unsigned flags); +#ifdef __NR_finit_module +# define finit_module(fd, uargs, flags) syscall(__NR_finit_module, fd, uargs, flags) +#endif /* linux/include/linux/module.h has limit of 64 chars on module names */ #undef MODULE_NAME_LEN #define MODULE_NAME_LEN 64 @@ -209,11 +213,34 @@ static int load_module(const char *fname, const char *options) int r; size_t len = MAXINT(ssize_t); char *module_image; + + if (!options) + options = ""; + dbg1_error_msg("load_module('%s','%s')", fname, options); - module_image = xmalloc_open_zipped_read_close(fname, &len); - r = (!module_image || init_module(module_image, len, options ? options : "") != 0); - free(module_image); + /* + * First we try finit_module if available. Some kernels are configured + * to only allow loading of modules off of secure storage (like a read- + * only rootfs) which needs the finit_module call. If it fails, we fall + * back to normal module loading to support compressed modules. + */ + r = 1; +# ifdef __NR_finit_module + { + int fd = open(fname, O_RDONLY | O_CLOEXEC); + if (fd >= 0) { + r = finit_module(fd, options, 0) != 0; + close(fd); + } + } +# endif + if (r != 0) { + module_image = xmalloc_open_zipped_read_close(fname, &len); + r = (!module_image || init_module(module_image, len, options) != 0); + free(module_image); + } + dbg1_error_msg("load_module:%d", r); return r; /* 0 = success */ #else diff --git a/modutils/modutils.c b/modutils/modutils.c index 0a056731d..d36caaf68 100644 --- a/modutils/modutils.c +++ b/modutils/modutils.c @@ -13,6 +13,9 @@ extern int delete_module(const char *module, unsigned int flags); #else # include # define init_module(mod, len, opts) syscall(__NR_init_module, mod, len, opts) +# if defined(__NR_finit_module) +# define finit_module(fd, uargs, flags) syscall(__NR_finit_module, fd, uargs, flags) +# endif # define delete_module(mod, flags) syscall(__NR_delete_module, mod, flags) #endif @@ -212,6 +215,24 @@ int FAST_FUNC bb_init_module(const char *filename, const char *options) return bb_init_module_24(filename, options); #endif + /* + * First we try finit_module if available. Some kernels are configured + * to only allow loading of modules off of secure storage (like a read- + * only rootfs) which needs the finit_module call. If it fails, we fall + * back to normal module loading to support compressed modules. + */ +# ifdef __NR_finit_module + { + int fd = open(filename, O_RDONLY | O_CLOEXEC); + if (fd >= 0) { + rc = finit_module(fd, options, 0) != 0; + close(fd); + if (rc == 0) + return rc; + } + } +# endif + image_size = INT_MAX - 4095; mmaped = 0; image = try_to_mmap_module(filename, &image_size); -- 2.25.1