From 786d7e1612f0b0adb6046f19b906609e4fe8b1ba Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Sun, 15 Jul 2007 23:39:00 -0700 Subject: Fix rmmod/read/write races in /proc entries Fix following races: =========================================== 1. Write via ->write_proc sleeps in copy_from_user(). Module disappears meanwhile. Or, more generically, system call done on /proc file, method supplied by module is called, module dissapeares meanwhile. pde = create_proc_entry() if (!pde) return -ENOMEM; pde->write_proc = ... open write copy_from_user pde = create_proc_entry(); if (!pde) { remove_proc_entry(); return -ENOMEM; /* module unloaded */ } *boom* ========================================== 2. bogo-revoke aka proc_kill_inodes() remove_proc_entry vfs_read proc_kill_inodes [check ->f_op validness] [check ->f_op->read validness] [verify_area, security permissions checks] ->f_op = NULL; if (file->f_op->read) /* ->f_op dereference, boom */ NOTE, NOTE, NOTE: file_operations are proxied for regular files only. Let's see how this scheme behaves, then extend if needed for directories. Directories creators in /proc only set ->owner for them, so proxying for directories may be unneeded. NOTE, NOTE, NOTE: methods being proxied are ->llseek, ->read, ->write, ->poll, ->unlocked_ioctl, ->ioctl, ->compat_ioctl, ->open, ->release. If your in-tree module uses something else, yell on me. Full audit pending. [akpm@linux-foundation.org: build fix] Signed-off-by: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/inode.c | 254 +++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 252 insertions(+), 2 deletions(-) (limited to 'fs/proc/inode.c') diff --git a/fs/proc/inode.c b/fs/proc/inode.c index d5ce65c68d7b..dd28e86ab422 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include @@ -140,6 +141,251 @@ static const struct super_operations proc_sops = { .remount_fs = proc_remount, }; +static void pde_users_dec(struct proc_dir_entry *pde) +{ + spin_lock(&pde->pde_unload_lock); + pde->pde_users--; + if (pde->pde_unload_completion && pde->pde_users == 0) + complete(pde->pde_unload_completion); + spin_unlock(&pde->pde_unload_lock); +} + +static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + loff_t rv = -EINVAL; + loff_t (*llseek)(struct file *, loff_t, int); + + spin_lock(&pde->pde_unload_lock); + /* + * remove_proc_entry() is going to delete PDE (as part of module + * cleanup sequence). No new callers into module allowed. + */ + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + /* + * Bump refcount so that remove_proc_entry will wail for ->llseek to + * complete. + */ + pde->pde_users++; + /* + * Save function pointer under lock, to protect against ->proc_fops + * NULL'ifying right after ->pde_unload_lock is dropped. + */ + llseek = pde->proc_fops->llseek; + spin_unlock(&pde->pde_unload_lock); + + if (!llseek) + llseek = default_llseek; + rv = llseek(file, offset, whence); + + pde_users_dec(pde); + return rv; +} + +static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + ssize_t rv = -EIO; + ssize_t (*read)(struct file *, char __user *, size_t, loff_t *); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + read = pde->proc_fops->read; + spin_unlock(&pde->pde_unload_lock); + + if (read) + rv = read(file, buf, count, ppos); + + pde_users_dec(pde); + return rv; +} + +static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + ssize_t rv = -EIO; + ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + write = pde->proc_fops->write; + spin_unlock(&pde->pde_unload_lock); + + if (write) + rv = write(file, buf, count, ppos); + + pde_users_dec(pde); + return rv; +} + +static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + unsigned int rv = 0; + unsigned int (*poll)(struct file *, struct poll_table_struct *); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + poll = pde->proc_fops->poll; + spin_unlock(&pde->pde_unload_lock); + + if (poll) + rv = poll(file, pts); + + pde_users_dec(pde); + return rv; +} + +static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + long rv = -ENOTTY; + long (*unlocked_ioctl)(struct file *, unsigned int, unsigned long); + int (*ioctl)(struct inode *, struct file *, unsigned int, unsigned long); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + unlocked_ioctl = pde->proc_fops->unlocked_ioctl; + ioctl = pde->proc_fops->ioctl; + spin_unlock(&pde->pde_unload_lock); + + if (unlocked_ioctl) { + rv = unlocked_ioctl(file, cmd, arg); + if (rv == -ENOIOCTLCMD) + rv = -EINVAL; + } else if (ioctl) { + lock_kernel(); + rv = ioctl(file->f_path.dentry->d_inode, file, cmd, arg); + unlock_kernel(); + } + + pde_users_dec(pde); + return rv; +} + +#ifdef CONFIG_COMPAT +static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + long rv = -ENOTTY; + long (*compat_ioctl)(struct file *, unsigned int, unsigned long); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + compat_ioctl = pde->proc_fops->compat_ioctl; + spin_unlock(&pde->pde_unload_lock); + + if (compat_ioctl) + rv = compat_ioctl(file, cmd, arg); + + pde_users_dec(pde); + return rv; +} +#endif + +static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + int rv = -EIO; + int (*mmap)(struct file *, struct vm_area_struct *); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + mmap = pde->proc_fops->mmap; + spin_unlock(&pde->pde_unload_lock); + + if (mmap) + rv = mmap(file, vma); + + pde_users_dec(pde); + return rv; +} + +static int proc_reg_open(struct inode *inode, struct file *file) +{ + struct proc_dir_entry *pde = PDE(inode); + int rv = 0; + int (*open)(struct inode *, struct file *); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + open = pde->proc_fops->open; + spin_unlock(&pde->pde_unload_lock); + + if (open) + rv = open(inode, file); + + pde_users_dec(pde); + return rv; +} + +static int proc_reg_release(struct inode *inode, struct file *file) +{ + struct proc_dir_entry *pde = PDE(inode); + int rv = 0; + int (*release)(struct inode *, struct file *); + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + release = pde->proc_fops->release; + spin_unlock(&pde->pde_unload_lock); + + if (release) + rv = release(inode, file); + + pde_users_dec(pde); + return rv; +} + +static const struct file_operations proc_reg_file_ops = { + .llseek = proc_reg_llseek, + .read = proc_reg_read, + .write = proc_reg_write, + .poll = proc_reg_poll, + .unlocked_ioctl = proc_reg_unlocked_ioctl, +#ifdef CONFIG_COMPAT + .compat_ioctl = proc_reg_compat_ioctl, +#endif + .mmap = proc_reg_mmap, + .open = proc_reg_open, + .release = proc_reg_release, +}; + struct inode *proc_get_inode(struct super_block *sb, unsigned int ino, struct proc_dir_entry *de) { @@ -166,8 +412,12 @@ struct inode *proc_get_inode(struct super_block *sb, unsigned int ino, inode->i_nlink = de->nlink; if (de->proc_iops) inode->i_op = de->proc_iops; - if (de->proc_fops) - inode->i_fop = de->proc_fops; + if (de->proc_fops) { + if (S_ISREG(inode->i_mode)) + inode->i_fop = &proc_reg_file_ops; + else + inode->i_fop = de->proc_fops; + } } return inode; -- cgit v1.2.3