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FROMLIST: configfs: make directories inherit uid/gid from creator

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Currently a non-root user may have the rights to create directories
in configfs, but they default to being owned by root, so you can't
create anything inside of the directories you yourself created.

phone:/config/usb_gadget/g1/configs $ id; mkdir b.2; ls -lZ; chown system:system b.2
uid=1000(system) gid=1000(system) groups=1000(system),1004(input),1007(log),1011(adb),...
drwxr-xr-x 3 system  system u:object_r:configfs:s0  0 2020-12-28 06:03 b.1
drwxr-xr-x 3 root    root   u:object_r:configfs:s0  0 2020-12-28 06:51 b.2
chown: 'b.2' to 'system:system': Operation not permitted

phone:/config/usb_gadget/g1/configs $ ln -s ../../../../usb_gadget/g1/functions/ffs.adb b.2/function0
ln: cannot create symbolic link from '../../../../usb_gadget/g1/functions/ffs.adb' to 'b.2/function0': Permission denied

Test: With this change b.2 is owned by system:system and the ln succeeds.
Link: https://lore.kernel.org/lkml/20210123205516.2738060-1-zenczykowski@gmail.com/
Bug: 172793258
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ia907b2def940197b44aa87b337d37c5dde9c5b91
This commit is contained in:
Maciej Żenczykowski 2020-12-28 06:42:35 -08:00
parent 54539dfef4
commit fa535cfd78
1 changed files with 15 additions and 0 deletions
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15
fs/configfs/dir.c
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@ -1409,6 +1409,21 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
else
ret = configfs_attach_item(parent_item, item, dentry, frag);
/* inherit uid/gid from process creating the directory */
if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID) ||
!gid_eq(current_fsgid(), GLOBAL_ROOT_GID)) {
struct iattr ia = {
.ia_uid = current_fsuid(),
.ia_gid = current_fsgid(),
.ia_valid = ATTR_UID | ATTR_GID,
};
struct inode *inode = d_inode(dentry);
inode->i_uid = ia.ia_uid;
inode->i_gid = ia.ia_gid;
/* the above manual assignments skip the permission checks */
configfs_setattr(dentry, &ia);
}
spin_lock(&configfs_dirent_lock);
sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
if (!ret)