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authorAl Viro <viro@zeniv.linux.org.uk>2019-05-12 13:18:42 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2019-05-25 17:59:55 -0400
commitfeb8ae43a7b33148028829b1b1691b28c874c952 (patch)
tree1670945a5204dba39d205c1c4c420025f159a035 /fs/super.c
parentf7a9945184100b531f0de3b12c617a349236dd8a (diff)
start massaging the checks in sget_...(): move to sget_userns()
there are 3 remaining callers of sget_userns() - sget(), mount_ns() and mount_pseudo_xattr(). Extra check in sget() is conditional upon mount being neither KERNMOUNT nor SUBMOUNT, the identical one in mount_ns() - upon being not KERNMOUNT; mount_pseudo_xattr() has no such checks at all. However, mount_ns() is never used with SUBMOUNT and mount_pseudo_xattr() is used only for KERNMOUNT, so both would be fine with the same logics as currently done in sget(), allowing to consolidate the entire thing in sget_userns() itself. That's not where these checks will end up in the long run, though - the whole reason why they'd been done so deep in the bowels of mount(2) was that there had been no way for a filesystem to specify which userns to look at until it has entered ->mount(). Now there is a place where filesystem could override the defaults - ->init_fs_context(). Which allows to pull the checks out into the callers of vfs_get_tree(). That'll take quite a bit of massage, but that mess is possible to tease apart. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/super.c')
-rw-r--r--fs/super.c14
1 files changed, 4 insertions, 10 deletions
diff --git a/fs/super.c b/fs/super.c
index 2739f57515f8..9c371a04e1b6 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -583,6 +583,10 @@ struct super_block *sget_userns(struct file_system_type *type,
struct super_block *old;
int err;
+ /* Ensure the requestor has permissions over the target filesystem */
+ if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+
if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) &&
!(type->fs_flags & FS_USERNS_MOUNT) &&
!capable(CAP_SYS_ADMIN))
@@ -653,10 +657,6 @@ struct super_block *sget(struct file_system_type *type,
if (flags & SB_SUBMOUNT)
user_ns = &init_user_ns;
- /* Ensure the requestor has permissions over the target filesystem */
- if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
- return ERR_PTR(-EPERM);
-
return sget_userns(type, test, set, flags, user_ns, data);
}
@@ -1164,12 +1164,6 @@ struct dentry *mount_ns(struct file_system_type *fs_type,
{
struct super_block *sb;
- /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
- * over the namespace.
- */
- if (!(flags & SB_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
- return ERR_PTR(-EPERM);
-
sb = sget_userns(fs_type, ns_test_super, ns_set_super, flags,
user_ns, ns);
if (IS_ERR(sb))