Tetsuo Handa wrote:
> [PATCH] LSM: Move security_path_chmod()/security_path_chown() to after mutex_lock().
>
> We should call security_path_chmod()/security_path_chown() after mutex_lock()
> in order to avoid races.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Acked-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
> ---
> fs/open.c | 36 +++++++++++++++---------------------
> 1 file changed, 15 insertions(+), 21 deletions(-)
>
> --- security-testing-2.6.orig/fs/open.c
> +++ security-testing-2.6/fs/open.c
> @@ -619,17 +619,17 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd
> err = mnt_want_write_file(file);
> if (err)
> goto out_putf;
> + mutex_lock(&inode->i_mutex);
> err = security_path_chmod(dentry, file->f_vfsmnt, mode);
> if (err)
> - goto out_drop_write;
> - mutex_lock(&inode->i_mutex);
> + goto out_unlock;
> if (mode == (mode_t) -1)
> mode = inode->i_mode;
> newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
> newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
> err = notify_change(dentry, &newattrs);
> +out_unlock:
> mutex_unlock(&inode->i_mutex);
> -out_drop_write:
> mnt_drop_write(file->f_path.mnt);
> out_putf:
> fput(file);
> @@ -652,17 +652,17 @@ SYSCALL_DEFINE3(fchmodat, int, dfd, cons
> error = mnt_want_write(path.mnt);
> if (error)
> goto dput_and_out;
> + mutex_lock(&inode->i_mutex);
> error = security_path_chmod(path.dentry, path.mnt, mode);
> if (error)
> - goto out_drop_write;
> - mutex_lock(&inode->i_mutex);
> + goto out_unlock;
> if (mode == (mode_t) -1)
> mode = inode->i_mode;
> newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
> newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
> error = notify_change(path.dentry, &newattrs);
> +out_unlock:
> mutex_unlock(&inode->i_mutex);
> -out_drop_write:
> mnt_drop_write(path.mnt);
> dput_and_out:
> path_put(&path);
> @@ -675,9 +675,9 @@ SYSCALL_DEFINE2(chmod, const char __user
> return sys_fchmodat(AT_FDCWD, filename, mode);
> }
>
> -static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
> +static int chown_common(struct path *path, uid_t user, gid_t group)
> {
> - struct inode *inode = dentry->d_inode;
> + struct inode *inode = path->dentry->d_inode;
> int error;
> struct iattr newattrs;
>
> @@ -694,7 +694,9 @@ static int chown_common(struct dentry *
> newattrs.ia_valid |=
> ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
> mutex_lock(&inode->i_mutex);
> - error = notify_change(dentry, &newattrs);
> + error = security_path_chown(path, user, group);
> + if (!error)
> + error = notify_change(path->dentry, &newattrs);
> mutex_unlock(&inode->i_mutex);
>
> return error;
> @@ -711,9 +713,7 @@ SYSCALL_DEFINE3(chown, const char __user
> error = mnt_want_write(path.mnt);
> if (error)
> goto out_release;
> - error = security_path_chown(&path, user, group);
> - if (!error)
> - error = chown_common(path.dentry, user, group);
> + error = chown_common(&path, user, group);
> mnt_drop_write(path.mnt);
> out_release:
> path_put(&path);
> @@ -738,9 +738,7 @@ SYSCALL_DEFINE5(fchownat, int, dfd, cons
> error = mnt_want_write(path.mnt);
> if (error)
> goto out_release;
> - error = security_path_chown(&path, user, group);
> - if (!error)
> - error = chown_common(path.dentry, user, group);
> + error = chown_common(&path, user, group);
> mnt_drop_write(path.mnt);
> out_release:
> path_put(&path);
> @@ -759,9 +757,7 @@ SYSCALL_DEFINE3(lchown, const char __use
> error = mnt_want_write(path.mnt);
> if (error)
> goto out_release;
> - error = security_path_chown(&path, user, group);
> - if (!error)
> - error = chown_common(path.dentry, user, group);
> + error = chown_common(&path, user, group);
> mnt_drop_write(path.mnt);
> out_release:
> path_put(&path);
> @@ -784,9 +780,7 @@ SYSCALL_DEFINE3(fchown, unsigned int, fd
> goto out_fput;
> dentry = file->f_path.dentry;
> audit_inode(NULL, dentry);
> - error = security_path_chown(&file->f_path, user, group);
> - if (!error)
> - error = chown_common(dentry, user, group);
> + error = chown_common(&file->f_path, user, group);
> mnt_drop_write(file->f_path.mnt);
> out_fput:
> fput(file);
>
> --
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