path: root/fs/fat/file.c
diff options
authorChristian Brauner <>2022-06-21 16:14:54 +0200
committerChristian Brauner (Microsoft) <>2022-06-26 18:18:56 +0200
commitb27c82e1296572cfa3997e58db3118a33915f85c (patch)
treeff3c2f626affd196f54ee985da02c81343e4050c /fs/fat/file.c
parent0e363cf3fa598c69340794da068d4d9cbc869322 (diff)
attr: port attribute changes to new types
Now that we introduced new infrastructure to increase the type safety for filesystems supporting idmapped mounts port the first part of the vfs over to them. This ports the attribute changes codepaths to rely on the new better helpers using a dedicated type. Before this change we used to take a shortcut and place the actual values that would be written to inode->i_{g,u}id into struct iattr. This had the advantage that we moved idmappings mostly out of the picture early on but it made reasoning about changes more difficult than it should be. The filesystem was never explicitly told that it dealt with an idmapped mount. The transition to the value that needed to be stored in inode->i_{g,u}id appeared way too early and increased the probability of bugs in various codepaths. We know place the same value in struct iattr no matter if this is an idmapped mount or not. The vfs will only deal with type safe vfs{g,u}id_t. This makes it massively safer to perform permission checks as the type will tell us what checks we need to perform and what helpers we need to use. Fileystems raising FS_ALLOW_IDMAP can't simply write ia_vfs{g,u}id to inode->i_{g,u}id since they are different types. Instead they need to use the dedicated vfs{g,u}id_to_k{g,u}id() helpers that map the vfs{g,u}id into the filesystem. The other nice effect is that filesystems like overlayfs don't need to care about idmappings explicitly anymore and can simply set up struct iattr accordingly directly. Link: [1] Link: Cc: Seth Forshee <> Cc: Christoph Hellwig <> Cc: Aleksa Sarai <> Cc: Linus Torvalds <> Cc: Al Viro <> CC: Reviewed-by: Seth Forshee <> Signed-off-by: Christian Brauner (Microsoft) <>
Diffstat (limited to 'fs/fat/file.c')
1 files changed, 5 insertions, 3 deletions
diff --git a/fs/fat/file.c b/fs/fat/file.c
index 530f18173db2..3e4eb3467cb4 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -90,7 +90,7 @@ static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
* out the RO attribute for checking by the security
* module, just because it maps to a file mode.
- err = security_inode_setattr(&init_user_ns,
+ err = security_inode_setattr(file_mnt_user_ns(file),
file->f_path.dentry, &ia);
if (err)
goto out_unlock_inode;
@@ -517,9 +517,11 @@ int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
if (((attr->ia_valid & ATTR_UID) &&
- (!uid_eq(attr->ia_uid, sbi->options.fs_uid))) ||
+ (!uid_eq(from_vfsuid(mnt_userns, i_user_ns(inode), attr->ia_vfsuid),
+ sbi->options.fs_uid))) ||
((attr->ia_valid & ATTR_GID) &&
- (!gid_eq(attr->ia_gid, sbi->options.fs_gid))) ||
+ (!gid_eq(from_vfsgid(mnt_userns, i_user_ns(inode), attr->ia_vfsgid),
+ sbi->options.fs_gid))) ||
((attr->ia_valid & ATTR_MODE) &&
(attr->ia_mode & ~FAT_VALID_MODE)))
error = -EPERM;