From 17f66065837415e0b1b4d619f12a2219af987c80 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Wed, 10 Oct 2012 14:23:18 +0300 Subject: mkfs.ubifs: rewrite path checking We use the 'in_path()' function to check whether the output image is withing the mkfs.ubifs root directory or not. However, this function is not correct and it fails for the following situation, as Marcus Prebble reports: 1. We have our root file-system mounted at / and want to build an image out of it. 2. We have tmpfs mounted at /tmp 3. We mount the root file-system under /tmp/newroot 4. We run mkfs.ubifs with -r /tmp/newroot -o /tmp/image And this fails. It fails because 'in_path()' misses this use-case. This patch re-implements the check completely. Now we use 'realpath()' to find canonical paths and just check that the output file is not under the root mkfs.ubifs directory. Reported-by: Marcus Prebble Signed-off-by: Artem Bityutskiy Tested-by: Marcus Prebble --- mkfs.ubifs/mkfs.ubifs.c | 116 +++++++++++++++--------------------------------- 1 file changed, 37 insertions(+), 79 deletions(-) diff --git a/mkfs.ubifs/mkfs.ubifs.c b/mkfs.ubifs/mkfs.ubifs.c index 46f12ad..5b433bd 100644 --- a/mkfs.ubifs/mkfs.ubifs.c +++ b/mkfs.ubifs/mkfs.ubifs.c @@ -20,6 +20,7 @@ * Zoltan Sogor */ +#define _XOPEN_SOURCE 500 /* For realpath() */ #define PROGRAM_NAME "mkfs.ubifs" #include "mkfs.ubifs.h" @@ -235,93 +236,50 @@ static char *make_path(const char *dir, const char *name) } /** - * same_dir - determine if two file descriptors refer to the same directory. - * @fd1: file descriptor 1 - * @fd2: file descriptor 2 - */ -static int same_dir(int fd1, int fd2) -{ - struct stat stat1, stat2; - - if (fstat(fd1, &stat1) == -1) - return -1; - if (fstat(fd2, &stat2) == -1) - return -1; - return stat1.st_dev == stat2.st_dev && stat1.st_ino == stat2.st_ino; -} - -/** - * do_openat - open a file in a directory. - * @fd: file descriptor of open directory - * @path: path relative to directory - * @flags: open flags + * is_contained - determine if a file is beneath a directory. + * @file: file path name + * @dir: directory path name * - * This function is provided because the library function openat is sometimes - * not available. + * This function returns %1 if @file is accessible from the @dir directory and + * %0 otherwise. In case of error, returns %-1. */ -static int do_openat(int fd, const char *path, int flags) +static int is_contained(const char *file, const char *dir) { - int ret; - char *cwd; + char *file_base, *copy, *real_file, *real_dir, *p; - cwd = getcwd(NULL, 0); - if (!cwd) + /* Make a copy of the file path because 'dirname()' can modify it */ + copy = strdup(file); + if (!copy) return -1; - ret = fchdir(fd); - if (ret != -1) - ret = open(path, flags); - if (chdir(cwd) && !ret) - ret = -1; - free(cwd); - return ret; -} + file_base = dirname(copy); -/** - * in_path - determine if a file is beneath a directory. - * @dir_name: directory path name - * @file_name: file path name - */ -static int in_path(const char *dir_name, const char *file_name) -{ - char *fn = strdup(file_name); - char *dn; - int fd1, fd2, fd3, ret = -1, top_fd; + /* Turn the paths into the canonical form */ + real_file = malloc(PATH_MAX); + if (!real_file) { + free(copy); + return -1; + } - if (!fn) + real_dir = malloc(PATH_MAX); + if (!real_dir) { + free(real_file); + free(copy); + return -1; + } + if (!realpath(file_base, real_file)) { + perror("realpath"); return -1; - top_fd = open("/", O_RDONLY); - if (top_fd != -1) { - dn = dirname(fn); - fd1 = open(dir_name, O_RDONLY); - if (fd1 != -1) { - fd2 = open(dn, O_RDONLY); - if (fd2 != -1) { - while (1) { - int same; - - same = same_dir(fd1, fd2); - if (same) { - ret = same; - break; - } - if (same_dir(fd2, top_fd)) { - ret = 0; - break; - } - fd3 = do_openat(fd2, "..", O_RDONLY); - if (fd3 == -1) - break; - close(fd2); - fd2 = fd3; - } - close(fd2); - } - close(fd1); - } - close(top_fd); } - free(fn); - return ret; + if (!realpath(dir, real_dir)) { + perror("realpath"); + return -1; + } + + p = strstr(real_file, real_dir); + free(real_dir); + free(real_file); + free(copy); + return !!p; } /** @@ -376,7 +334,7 @@ static int validate_options(void) if (!output) return err_msg("no output file or UBI volume specified"); - if (root && in_path(root, output)) + if (root && is_contained(output, root)) return err_msg("output file cannot be in the UBIFS root " "directory"); if (!is_power_of_2(c->min_io_size)) -- cgit v1.2.3