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Subject[PATCH v3 2/4] vfs,userns: Ensure real root is always capable towards inodes
Date
Currently root is restricted from performing some modifications
to inodes whose owner is INVALID_UID or group is INVALID_GID
because this id doesn't map into any user namespace. Add a
special case to the relevant checks to make sure root is always
capable of performing these operations.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
fs/inode.c | 3 +++
kernel/capability.c | 6 +++++-
2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/inode.c b/fs/inode.c
index 26753ba7b6d6..1029320ff029 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1840,6 +1840,9 @@ bool inode_owner_or_capable(const struct inode *inode)
{
struct user_namespace *ns;

+ if (capable(CAP_SYS_ADMIN))
+ return true;
+
if (uid_eq(current_fsuid(), inode->i_uid))
return true;

diff --git a/kernel/capability.c b/kernel/capability.c
index 989f5bfc57dc..a472eaa52b6a 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -438,8 +438,12 @@ EXPORT_SYMBOL(capable);
*/
bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
{
- struct user_namespace *ns = current_user_ns();
+ struct user_namespace *ns;

+ if (capable(CAP_SYS_ADMIN))
+ return true;
+
+ ns = current_user_ns();
return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
kgid_has_mapping(ns, inode->i_gid);
}
--
1.9.1


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