diff options
| -rw-r--r-- | fs/inode.c | 36 | ||||
| -rw-r--r-- | include/linux/fs.h | 2 |
2 files changed, 34 insertions, 4 deletions
diff --git a/fs/inode.c b/fs/inode.c index bd4da9c5207e..71b36afc3893 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -2246,10 +2246,8 @@ void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode, /* Directories are special, and always inherit S_ISGID */ if (S_ISDIR(mode)) mode |= S_ISGID; - else if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP) && - !in_group_p(i_gid_into_mnt(mnt_userns, dir)) && - !capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID)) - mode &= ~S_ISGID; + else + mode = mode_strip_sgid(mnt_userns, dir, mode); } else inode_fsgid_set(inode, mnt_userns); inode->i_mode = mode; @@ -2405,3 +2403,33 @@ struct timespec64 current_time(struct inode *inode) return timestamp_truncate(now, inode); } EXPORT_SYMBOL(current_time); + +/** + * mode_strip_sgid - handle the sgid bit for non-directories + * @mnt_userns: User namespace of the mount the inode was created from + * @dir: parent directory inode + * @mode: mode of the file to be created in @dir + * + * If the @mode of the new file has both the S_ISGID and S_IXGRP bit + * raised and @dir has the S_ISGID bit raised ensure that the caller is + * either in the group of the parent directory or they have CAP_FSETID + * in their user namespace and are privileged over the parent directory. + * In all other cases, strip the S_ISGID bit from @mode. + * + * Return: the new mode to use for the file + */ +umode_t mode_strip_sgid(struct user_namespace *mnt_userns, + const struct inode *dir, umode_t mode) +{ + if ((mode & (S_ISGID | S_IXGRP)) != (S_ISGID | S_IXGRP)) + return mode; + if (S_ISDIR(mode) || !dir || !(dir->i_mode & S_ISGID)) + return mode; + if (in_group_p(i_gid_into_mnt(mnt_userns, dir))) + return mode; + if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID)) + return mode; + + return mode & ~S_ISGID; +} +EXPORT_SYMBOL(mode_strip_sgid); diff --git a/include/linux/fs.h b/include/linux/fs.h index 9ad5e3520fae..50642668c60f 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1903,6 +1903,8 @@ extern long compat_ptr_ioctl(struct file *file, unsigned int cmd, void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode, const struct inode *dir, umode_t mode); extern bool may_open_dev(const struct path *path); +umode_t mode_strip_sgid(struct user_namespace *mnt_userns, + const struct inode *dir, umode_t mode); /* * This is the "filldir" function type, used by readdir() to let |