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| author |   Miklos Szeredi <mszeredi@redhat.com> | 2020-05-14 16:44:23 +0200 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-05-14 16:44:23 +0200 |
| commit | a3c751a50fe6bbe50eb7622a14b18b361804ee0c (patch) | |
| tree | c06d4a05f89fea5d5ea3f4729ab6748140bbb77a /include | |
| parent | Linux 5.7-rc4 (diff) | |
| download | wireguard-linux-a3c751a50fe6bbe50eb7622a14b18b361804ee0c.tar.xz wireguard-linux-a3c751a50fe6bbe50eb7622a14b18b361804ee0c.zip | |
vfs: allow unprivileged whiteout creation
Whiteouts, unlike real device node should not require privileges to create.
The general concern with device nodes is that opening them can have side
effects. The kernel already avoids zero major (see
Documentation/admin-guide/devices.txt). To be on the safe side the patch
explicitly forbids registering a char device with 0/0 number (see
cdev_add()).
This guarantees that a non-O_PATH open on a whiteout will fail with ENODEV;
i.e. it won't have any side effect.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/device_cgroup.h | 3 | ||||
| -rw-r--r-- | include/linux/fs.h | 6 |
2 files changed, 8 insertions, 1 deletions
diff --git a/include/linux/device_cgroup.h b/include/linux/device_cgroup.h index fa35b52e0002..57e63bd63370 100644 --- a/include/linux/device_cgroup.h +++ b/include/linux/device_cgroup.h @@ -51,6 +51,9 @@ static inline int devcgroup_inode_mknod(int mode, dev_t dev) if (!S_ISBLK(mode) && !S_ISCHR(mode)) return 0; + if (S_ISCHR(mode) && dev == WHITEOUT_DEV) + return 0; + if (S_ISBLK(mode)) type = DEVCG_DEV_BLOCK; else diff --git a/include/linux/fs.h b/include/linux/fs.h index 4f6f59b4f22a..15665ef1ef90 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1721,7 +1721,11 @@ extern int vfs_link(struct dentry *, struct inode *, struct dentry *, struct ino extern int vfs_rmdir(struct inode *, struct dentry *); extern int vfs_unlink(struct inode *, struct dentry *, struct inode **); extern int vfs_rename(struct inode *, struct dentry *, struct inode *, struct dentry *, struct inode **, unsigned int); -extern int vfs_whiteout(struct inode *, struct dentry *); + +static inline int vfs_whiteout(struct inode *dir, struct dentry *dentry) +{ + return vfs_mknod(dir, dentry, S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV); +} extern struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode, int open_flag); |