From 2527b284defaeadf74829b0b0bd3207ca7f165eb Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 12 May 2019 17:09:01 -0400 Subject: move the capability checks from sget_userns() to legacy_get_tree() 1) all call chains leading to sget_userns() pass through ->mount() instances. 2) none of ->mount() instances is ever called directly - the only call site is legacy_get_tree() 3) all remaining ->mount() instances end up calling sget_userns() IOW, we might as well do the capability checks just before calling ->mount(). As for the arguments passed to mount_capable(), in case of call chains to sget_userns() going through sget(), we either don't call mount_capable() at all, or pass current_user_ns() to it. The call chains going through mount_pseudo_xattr() don't call mount_capable() at all (SB_KERNMOUNT in flags on those). That could've been split into smaller steps (lifting the checks into sget(), then callers of sget(), then all the way to the entries of every ->mount() out there, then to the sole caller), but that would be too much churn for little benefit... Signed-off-by: Al Viro --- fs/super.c | 4 ---- 1 file changed, 4 deletions(-) (limited to 'fs/super.c') diff --git a/fs/super.c b/fs/super.c index 6919f5c728f0..bdb03255c7ea 100644 --- a/fs/super.c +++ b/fs/super.c @@ -583,10 +583,6 @@ struct super_block *sget_userns(struct file_system_type *type, struct super_block *old; int err; - if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT))) { - if (!mount_capable(type, user_ns)) - return ERR_PTR(-EPERM); - } retry: spin_lock(&sb_lock); if (test) { -- cgit