diff options
Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 275 |
1 files changed, 209 insertions, 66 deletions
diff --git a/fs/namei.c b/fs/namei.c index 8cf9bb9c2fc..e179f71bfcb 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1623,8 +1623,7 @@ int may_open(struct nameidata *nd, int acc_mode, int flag) return -EACCES; flag &= ~O_TRUNC; - } else if (IS_RDONLY(inode) && (acc_mode & MAY_WRITE)) - return -EROFS; + } error = vfs_permission(nd, acc_mode); if (error) @@ -1677,7 +1676,12 @@ int may_open(struct nameidata *nd, int acc_mode, int flag) return 0; } -static int open_namei_create(struct nameidata *nd, struct path *path, +/* + * Be careful about ever adding any more callers of this + * function. Its flags must be in the namei format, not + * what get passed to sys_open(). + */ +static int __open_namei_create(struct nameidata *nd, struct path *path, int flag, int mode) { int error; @@ -1696,26 +1700,56 @@ static int open_namei_create(struct nameidata *nd, struct path *path, } /* - * open_namei() + * Note that while the flag value (low two bits) for sys_open means: + * 00 - read-only + * 01 - write-only + * 10 - read-write + * 11 - special + * it is changed into + * 00 - no permissions needed + * 01 - read-permission + * 10 - write-permission + * 11 - read-write + * for the internal routines (ie open_namei()/follow_link() etc) + * This is more logical, and also allows the 00 "no perm needed" + * to be used for symlinks (where the permissions are checked + * later). * - * namei for open - this is in fact almost the whole open-routine. - * - * Note that the low bits of "flag" aren't the same as in the open - * system call - they are 00 - no permissions needed - * 01 - read permission needed - * 10 - write permission needed - * 11 - read/write permissions needed - * which is a lot more logical, and also allows the "no perm" needed - * for symlinks (where the permissions are checked later). - * SMP-safe +*/ +static inline int open_to_namei_flags(int flag) +{ + if ((flag+1) & O_ACCMODE) + flag++; + return flag; +} + +static int open_will_write_to_fs(int flag, struct inode *inode) +{ + /* + * We'll never write to the fs underlying + * a device file. + */ + if (special_file(inode->i_mode)) + return 0; + return (flag & O_TRUNC); +} + +/* + * Note that the low bits of the passed in "open_flag" + * are not the same as in the local variable "flag". See + * open_to_namei_flags() for more details. */ -int open_namei(int dfd, const char *pathname, int flag, - int mode, struct nameidata *nd) +struct file *do_filp_open(int dfd, const char *pathname, + int open_flag, int mode) { + struct file *filp; + struct nameidata nd; int acc_mode, error; struct path path; struct dentry *dir; int count = 0; + int will_write; + int flag = open_to_namei_flags(open_flag); acc_mode = ACC_MODE(flag); @@ -1733,18 +1767,19 @@ int open_namei(int dfd, const char *pathname, int flag, */ if (!(flag & O_CREAT)) { error = path_lookup_open(dfd, pathname, lookup_flags(flag), - nd, flag); + &nd, flag); if (error) - return error; + return ERR_PTR(error); goto ok; } /* * Create - we need to know the parent. */ - error = path_lookup_create(dfd,pathname,LOOKUP_PARENT,nd,flag,mode); + error = path_lookup_create(dfd, pathname, LOOKUP_PARENT, + &nd, flag, mode); if (error) - return error; + return ERR_PTR(error); /* * We have the parent and last component. First of all, check @@ -1752,14 +1787,14 @@ int open_namei(int dfd, const char *pathname, int flag, * will not do. */ error = -EISDIR; - if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len]) + if (nd.last_type != LAST_NORM || nd.last.name[nd.last.len]) goto exit; - dir = nd->path.dentry; - nd->flags &= ~LOOKUP_PARENT; + dir = nd.path.dentry; + nd.flags &= ~LOOKUP_PARENT; mutex_lock(&dir->d_inode->i_mutex); - path.dentry = lookup_hash(nd); - path.mnt = nd->path.mnt; + path.dentry = lookup_hash(&nd); + path.mnt = nd.path.mnt; do_last: error = PTR_ERR(path.dentry); @@ -1768,18 +1803,31 @@ do_last: goto exit; } - if (IS_ERR(nd->intent.open.file)) { - mutex_unlock(&dir->d_inode->i_mutex); - error = PTR_ERR(nd->intent.open.file); - goto exit_dput; + if (IS_ERR(nd.intent.open.file)) { + error = PTR_ERR(nd.intent.open.file); + goto exit_mutex_unlock; } /* Negative dentry, just create the file */ if (!path.dentry->d_inode) { - error = open_namei_create(nd, &path, flag, mode); + /* + * This write is needed to ensure that a + * ro->rw transition does not occur between + * the time when the file is created and when + * a permanent write count is taken through + * the 'struct file' in nameidata_to_filp(). + */ + error = mnt_want_write(nd.path.mnt); if (error) + goto exit_mutex_unlock; + error = __open_namei_create(&nd, &path, flag, mode); + if (error) { + mnt_drop_write(nd.path.mnt); goto exit; - return 0; + } + filp = nameidata_to_filp(&nd, open_flag); + mnt_drop_write(nd.path.mnt); + return filp; } /* @@ -1804,23 +1852,52 @@ do_last: if (path.dentry->d_inode->i_op && path.dentry->d_inode->i_op->follow_link) goto do_link; - path_to_nameidata(&path, nd); + path_to_nameidata(&path, &nd); error = -EISDIR; if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode)) goto exit; ok: - error = may_open(nd, acc_mode, flag); - if (error) + /* + * Consider: + * 1. may_open() truncates a file + * 2. a rw->ro mount transition occurs + * 3. nameidata_to_filp() fails due to + * the ro mount. + * That would be inconsistent, and should + * be avoided. Taking this mnt write here + * ensures that (2) can not occur. + */ + will_write = open_will_write_to_fs(flag, nd.path.dentry->d_inode); + if (will_write) { + error = mnt_want_write(nd.path.mnt); + if (error) + goto exit; + } + error = may_open(&nd, acc_mode, flag); + if (error) { + if (will_write) + mnt_drop_write(nd.path.mnt); goto exit; - return 0; + } + filp = nameidata_to_filp(&nd, open_flag); + /* + * It is now safe to drop the mnt write + * because the filp has had a write taken + * on its behalf. + */ + if (will_write) + mnt_drop_write(nd.path.mnt); + return filp; +exit_mutex_unlock: + mutex_unlock(&dir->d_inode->i_mutex); exit_dput: - path_put_conditional(&path, nd); + path_put_conditional(&path, &nd); exit: - if (!IS_ERR(nd->intent.open.file)) - release_open_intent(nd); - path_put(&nd->path); - return error; + if (!IS_ERR(nd.intent.open.file)) + release_open_intent(&nd); + path_put(&nd.path); + return ERR_PTR(error); do_link: error = -ELOOP; @@ -1836,43 +1913,60 @@ do_link: * stored in nd->last.name and we will have to putname() it when we * are done. Procfs-like symlinks just set LAST_BIND. */ - nd->flags |= LOOKUP_PARENT; - error = security_inode_follow_link(path.dentry, nd); + nd.flags |= LOOKUP_PARENT; + error = security_inode_follow_link(path.dentry, &nd); if (error) goto exit_dput; - error = __do_follow_link(&path, nd); + error = __do_follow_link(&path, &nd); if (error) { /* Does someone understand code flow here? Or it is only * me so stupid? Anathema to whoever designed this non-sense * with "intent.open". */ - release_open_intent(nd); - return error; + release_open_intent(&nd); + return ERR_PTR(error); } - nd->flags &= ~LOOKUP_PARENT; - if (nd->last_type == LAST_BIND) + nd.flags &= ~LOOKUP_PARENT; + if (nd.last_type == LAST_BIND) goto ok; error = -EISDIR; - if (nd->last_type != LAST_NORM) + if (nd.last_type != LAST_NORM) goto exit; - if (nd->last.name[nd->last.len]) { - __putname(nd->last.name); + if (nd.last.name[nd.last.len]) { + __putname(nd.last.name); goto exit; } error = -ELOOP; if (count++==32) { - __putname(nd->last.name); + __putname(nd.last.name); goto exit; } - dir = nd->path.dentry; + dir = nd.path.dentry; mutex_lock(&dir->d_inode->i_mutex); - path.dentry = lookup_hash(nd); - path.mnt = nd->path.mnt; - __putname(nd->last.name); + path.dentry = lookup_hash(&nd); + path.mnt = nd.path.mnt; + __putname(nd.last.name); goto do_last; } /** + * filp_open - open file and return file pointer + * + * @filename: path to open + * @flags: open flags as per the open(2) second argument + * @mode: mode for the new file if O_CREAT is set, else ignored + * + * This is the helper to open a file from kernelspace if you really + * have to. But in generally you should not do this, so please move + * along, nothing to see here.. + */ +struct file *filp_open(const char *filename, int flags, int mode) +{ + return do_filp_open(AT_FDCWD, filename, flags, mode); +} +EXPORT_SYMBOL(filp_open); + +/** * lookup_create - lookup a dentry, creating it if it doesn't exist * @nd: nameidata info * @is_dir: directory flag @@ -1945,6 +2039,23 @@ int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) return error; } +static int may_mknod(mode_t mode) +{ + switch (mode & S_IFMT) { + case S_IFREG: + case S_IFCHR: + case S_IFBLK: + case S_IFIFO: + case S_IFSOCK: + case 0: /* zero mode translates to S_IFREG */ + return 0; + case S_IFDIR: + return -EPERM; + default: + return -EINVAL; + } +} + asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode, unsigned dev) { @@ -1963,12 +2074,19 @@ asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode, if (error) goto out; dentry = lookup_create(&nd, 0); - error = PTR_ERR(dentry); - + if (IS_ERR(dentry)) { + error = PTR_ERR(dentry); + goto out_unlock; + } if (!IS_POSIXACL(nd.path.dentry->d_inode)) mode &= ~current->fs->umask; - if (!IS_ERR(dentry)) { - switch (mode & S_IFMT) { + error = may_mknod(mode); + if (error) + goto out_dput; + error = mnt_want_write(nd.path.mnt); + if (error) + goto out_dput; + switch (mode & S_IFMT) { case 0: case S_IFREG: error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd); break; @@ -1979,14 +2097,11 @@ asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode, case S_IFIFO: case S_IFSOCK: error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0); break; - case S_IFDIR: - error = -EPERM; - break; - default: - error = -EINVAL; - } - dput(dentry); } + mnt_drop_write(nd.path.mnt); +out_dput: + dput(dentry); +out_unlock: mutex_unlock(&nd.path.dentry->d_inode->i_mutex); path_put(&nd.path); out: @@ -2044,7 +2159,12 @@ asmlinkage long sys_mkdirat(int dfd, const char __user *pathname, int mode) if (!IS_POSIXACL(nd.path.dentry->d_inode)) mode &= ~current->fs->umask; + error = mnt_want_write(nd.path.mnt); + if (error) + goto out_dput; error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode); + mnt_drop_write(nd.path.mnt); +out_dput: dput(dentry); out_unlock: mutex_unlock(&nd.path.dentry->d_inode->i_mutex); @@ -2151,7 +2271,12 @@ static long do_rmdir(int dfd, const char __user *pathname) error = PTR_ERR(dentry); if (IS_ERR(dentry)) goto exit2; + error = mnt_want_write(nd.path.mnt); + if (error) + goto exit3; error = vfs_rmdir(nd.path.dentry->d_inode, dentry); + mnt_drop_write(nd.path.mnt); +exit3: dput(dentry); exit2: mutex_unlock(&nd.path.dentry->d_inode->i_mutex); @@ -2232,7 +2357,11 @@ static long do_unlinkat(int dfd, const char __user *pathname) inode = dentry->d_inode; if (inode) atomic_inc(&inode->i_count); + error = mnt_want_write(nd.path.mnt); + if (error) + goto exit2; error = vfs_unlink(nd.path.dentry->d_inode, dentry); + mnt_drop_write(nd.path.mnt); exit2: dput(dentry); } @@ -2313,7 +2442,12 @@ asmlinkage long sys_symlinkat(const char __user *oldname, if (IS_ERR(dentry)) goto out_unlock; + error = mnt_want_write(nd.path.mnt); + if (error) + goto out_dput; error = vfs_symlink(nd.path.dentry->d_inode, dentry, from, S_IALLUGO); + mnt_drop_write(nd.path.mnt); +out_dput: dput(dentry); out_unlock: mutex_unlock(&nd.path.dentry->d_inode->i_mutex); @@ -2408,7 +2542,12 @@ asmlinkage long sys_linkat(int olddfd, const char __user *oldname, error = PTR_ERR(new_dentry); if (IS_ERR(new_dentry)) goto out_unlock; + error = mnt_want_write(nd.path.mnt); + if (error) + goto out_dput; error = vfs_link(old_nd.path.dentry, nd.path.dentry->d_inode, new_dentry); + mnt_drop_write(nd.path.mnt); +out_dput: dput(new_dentry); out_unlock: mutex_unlock(&nd.path.dentry->d_inode->i_mutex); @@ -2634,8 +2773,12 @@ static int do_rename(int olddfd, const char *oldname, if (new_dentry == trap) goto exit5; + error = mnt_want_write(oldnd.path.mnt); + if (error) + goto exit5; error = vfs_rename(old_dir->d_inode, old_dentry, new_dir->d_inode, new_dentry); + mnt_drop_write(oldnd.path.mnt); exit5: dput(new_dentry); exit4: |