>From 45b430985585164fe2d600795805f6d02b04ac96 Mon Sep 17 00:00:00 2001 From: Dmitry Torokhov Date: Sun, 14 Nov 2021 14:25:27 -0800 Subject: [PATCH] kmod: add support for passing compressed modules directly into kernel Kernel's load pinning facilities interfere with loading compressed modules, because if decompression happens in userspace and module is instantiated via init_module() call there is no way for kernel to ascertain that module data is coming from a trusted source. To solve this issue module decompression support was added to the kernel. Let's use the new kernel facility, and if kernel indicates (via /sys/module/compression) that that it can handle certain compression scheme, then use finit_module() and pass a file descriptor to the compressed module instead of init_module() with decompressed data. --- libkmod/libkmod-file.c | 41 +++++++++++++++++++------------------- libkmod/libkmod-internal.h | 9 ++++++++- libkmod/libkmod-module.c | 41 +++++++++++++++++++++++++++++++++++++- shared/missing.h | 4 ++++ 4 files changed, 73 insertions(+), 22 deletions(-) diff --git a/libkmod/libkmod-file.c b/libkmod/libkmod-file.c index b6a8cc9..9f1b99e 100644 --- a/libkmod/libkmod-file.c +++ b/libkmod/libkmod-file.c @@ -48,17 +48,11 @@ struct file_ops { }; struct kmod_file { -#ifdef ENABLE_ZSTD - bool zstd_used; -#endif -#ifdef ENABLE_XZ - bool xz_used; -#endif + enum kmod_compression compression; #ifdef ENABLE_ZLIB gzFile gzf; #endif int fd; - bool direct; off_t size; void *memory; const struct file_ops *ops; @@ -179,7 +173,7 @@ static int load_zstd(struct kmod_file *file) ZSTD_freeDStream(dstr); free((void *)zst_inb.src); - file->zstd_used = true; + file->compression = KMOD_COMPRESSION_ZSTD; file->memory = zst_outb.dst; file->size = zst_outb.pos; return 0; @@ -193,7 +187,7 @@ out: static void unload_zstd(struct kmod_file *file) { - if (!file->zstd_used) + if (file->compression != KMOD_COMPRESSION_ZSTD) return; free(file->memory); } @@ -272,7 +266,7 @@ static int xz_uncompress(lzma_stream *strm, struct kmod_file *file) goto out; } } - file->xz_used = true; + file->compression = KMOD_COMPRESSION_XZ; file->memory = p; file->size = total; return 0; @@ -302,7 +296,7 @@ static int load_xz(struct kmod_file *file) static void unload_xz(struct kmod_file *file) { - if (!file->xz_used) + if (file->compression != KMOD_COMPRESSION_XZ) return; free(file->memory); } @@ -314,15 +308,20 @@ static const char magic_xz[] = {0xfd, '7', 'z', 'X', 'Z', 0}; #define READ_STEP (4 * 1024 * 1024) static int load_zlib(struct kmod_file *file) { + int gzf_fd; int err = 0; off_t did = 0, total = 0; _cleanup_free_ unsigned char *p = NULL; errno = 0; - file->gzf = gzdopen(file->fd, "rb"); + + gzf_fd = dup(file->fd); + if (gzf_fd < 0) + return -errno; + + file->gzf = gzdopen(gzf_fd, "rb"); if (file->gzf == NULL) return -errno; - file->fd = -1; /* now owned by gzf due gzdopen() */ for (;;) { int r; @@ -353,22 +352,24 @@ static int load_zlib(struct kmod_file *file) did += r; } + file->compression = KMOD_COMPRESSION_GZIP; file->memory = p; file->size = did; p = NULL; return 0; error: - gzclose(file->gzf); + if (file->gzf) + gzclose(file->gzf); return err; } static void unload_zlib(struct kmod_file *file) { - if (file->gzf == NULL) + if (file->compression != KMOD_COMPRESSION_GZIP) return; free(file->memory); - gzclose(file->gzf); /* closes file->fd */ + gzclose(file->gzf); } static const char magic_zlib[] = {0x1f, 0x8b}; @@ -403,7 +404,8 @@ static int load_reg(struct kmod_file *file) file->fd, 0); if (file->memory == MAP_FAILED) return -errno; - file->direct = true; + + file->compression = KMOD_COMPRESSION_NONE; return 0; } @@ -447,7 +449,6 @@ struct kmod_file *kmod_file_open(const struct kmod_ctx *ctx, magic_size_max = itr->magic_size; } - file->direct = false; if (magic_size_max > 0) { char *buf = alloca(magic_size_max + 1); ssize_t sz; @@ -501,9 +502,9 @@ off_t kmod_file_get_size(const struct kmod_file *file) return file->size; } -bool kmod_file_get_direct(const struct kmod_file *file) +enum kmod_compression kmod_file_get_compression(const struct kmod_file *file) { - return file->direct; + return file->compression; } int kmod_file_get_fd(const struct kmod_file *file) diff --git a/libkmod/libkmod-internal.h b/libkmod/libkmod-internal.h index c22644a..a8405b3 100644 --- a/libkmod/libkmod-internal.h +++ b/libkmod/libkmod-internal.h @@ -48,6 +48,13 @@ static _always_inline_ _printf_format_(2, 3) void # endif #endif +enum kmod_compression { + KMOD_COMPRESSION_NONE, + KMOD_COMPRESSION_GZIP, + KMOD_COMPRESSION_XZ, + KMOD_COMPRESSION_ZSTD, +}; + void kmod_log(const struct kmod_ctx *ctx, int priority, const char *file, int line, const char *fn, const char *format, ...) __attribute__((format(printf, 6, 7))) __attribute__((nonnull(1, 3, 5))); @@ -155,7 +162,7 @@ struct kmod_file *kmod_file_open(const struct kmod_ctx *ctx, const char *filenam struct kmod_elf *kmod_file_get_elf(struct kmod_file *file) __attribute__((nonnull(1))); void *kmod_file_get_contents(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1))); off_t kmod_file_get_size(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1))); -bool kmod_file_get_direct(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1))); +enum kmod_compression kmod_file_get_compression(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1))); int kmod_file_get_fd(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1))); void kmod_file_unref(struct kmod_file *file) __attribute__((nonnull(1))); diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c index 6e0ff1a..dd38848 100644 --- a/libkmod/libkmod-module.c +++ b/libkmod/libkmod-module.c @@ -802,6 +802,39 @@ KMOD_EXPORT int kmod_module_remove_module(struct kmod_module *mod, return err; } +static enum kmod_compression kmod_get_supported_compression(struct kmod_module *mod) +{ + static const char path[] = "/sys/module/compression"; + char buf[16]; + int err; + int fd; + + fd = open(path, O_RDONLY|O_CLOEXEC); + if (fd < 0) { + DBG(mod->ctx, "could not open '%s': %s\n", + path, strerror(errno)); + goto fail; + } + + err = read_str_safe(fd, buf, sizeof(buf)); + close(fd); + if (err < 0) { + ERR(mod->ctx, "could not read from '%s': %s\n", + path, strerror(-err)); + goto fail; + } + + if (streq(buf, "gzip\n")) + return KMOD_COMPRESSION_GZIP; + else if (streq(buf, "xz\n")) + return KMOD_COMPRESSION_XZ; + else if (streq(buf, "zstd\n")) + return KMOD_COMPRESSION_ZSTD; + +fail: + return KMOD_COMPRESSION_NONE; +} + extern long init_module(const void *mem, unsigned long len, const char *args); /** @@ -829,6 +862,7 @@ KMOD_EXPORT int kmod_module_insert_module(struct kmod_module *mod, struct kmod_elf *elf; const char *path; const char *args = options ? options : ""; + enum kmod_compression compression; if (mod == NULL) return -ENOENT; @@ -847,7 +881,9 @@ KMOD_EXPORT int kmod_module_insert_module(struct kmod_module *mod, } } - if (kmod_file_get_direct(mod->file)) { + compression = kmod_file_get_compression(mod->file); + if (compression == KMOD_COMPRESSION_NONE || + compression == kmod_get_supported_compression(mod)) { unsigned int kernel_flags = 0; if (flags & KMOD_INSERT_FORCE_VERMAGIC) @@ -855,6 +891,9 @@ KMOD_EXPORT int kmod_module_insert_module(struct kmod_module *mod, if (flags & KMOD_INSERT_FORCE_MODVERSION) kernel_flags |= MODULE_INIT_IGNORE_MODVERSIONS; + if (compression != KMOD_COMPRESSION_NONE) + kernel_flags |= MODULE_INIT_COMPRESSED_DATA; + err = finit_module(kmod_file_get_fd(mod->file), args, kernel_flags); if (err == 0 || errno != ENOSYS) goto init_finished; diff --git a/shared/missing.h b/shared/missing.h index 4c0d136..f1e68b6 100644 --- a/shared/missing.h +++ b/shared/missing.h @@ -15,6 +15,10 @@ # define MODULE_INIT_IGNORE_VERMAGIC 2 #endif +#ifndef MODULE_INIT_COMPRESSED_DATA +# define MODULE_INIT_COMPRESSED_DATA 4 +#endif + #ifndef __NR_finit_module # define __NR_finit_module -1 #endif -- 2.34.0.rc2.393.gf8c9666880-goog