[PATCH v5 33/42] apparmor: handle idmapped mounts

Christian Brauner
2021-01-12T22:17:28Z

The i_uid and i_gid are only ever used when logging for AppArmor. This
is already broken in a bunch of places where the global root id is
reported instead of the i_uid or i_gid of the file. Nonetheless, be kind
and log the mapped inode if we're coming from an idmapped mount. If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged

/* v3 */
unchanged

/* v4 */
- Serge Hallyn <serge@hallyn.com>:
- Use "mnt_userns" to refer to a vfsmount's userns everywhere to make
terminology consistent.

/* v5 */
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837

- Christoph Hellwig <hch@lst.de>:
- Use new file_userns_helper().
---
security/apparmor/domain.c | 9 ++++++---
security/apparmor/file.c | 5 ++++-
security/apparmor/lsm.c | 12 ++++++++----
3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 16f184bc48de..9a1b31655d9e 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -10,12 +10,14 @@

#include <linux/errno.h>
#include <linux/fdtable.h>
+#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>
#include <linux/personality.h>
#include <linux/xattr.h>
+#include <linux/user_namespace.h>

#include "include/audit.h"
#include "include/apparmorfs.h"
@@ -858,8 +860,10 @@ int apparmor_bprm_creds_for_exec(struct linux_binprm *bprm)
const char *info = NULL;
int error = 0;
bool unsafe = false;
+ struct user_namespace *mnt_userns = file_user_ns(bprm->file);
+ kuid_t i_uid = i_uid_into_mnt(mnt_userns, file_inode(bprm->file));
struct path_cond cond = {
- file_inode(bprm->file)->i_uid,
+ i_uid,
file_inode(bprm->file)->i_mode
};

@@ -967,8 +971,7 @@ int apparmor_bprm_creds_for_exec(struct linux_binprm *bprm)
error = fn_for_each(label, profile,
aa_audit_file(profile, &nullperms, OP_EXEC, MAY_EXEC,
bprm->filename, NULL, new,
- file_inode(bprm->file)->i_uid, info,
- error));
+ i_uid, info, error));
aa_put_label(new);
goto done;
}
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index 92acf9a49405..a00db7eaefc8 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -11,6 +11,8 @@
#include <linux/tty.h>
#include <linux/fdtable.h>
#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/mount.h>

#include "include/apparmor.h"
#include "include/audit.h"
@@ -508,8 +510,9 @@ static int __file_path_perm(const char *op, struct aa_label *label,
{
struct aa_profile *profile;
struct aa_perms perms = {};
+ struct user_namespace *mnt_userns = file_user_ns(file);
struct path_cond cond = {
- .uid = file_inode(file)->i_uid,
+ .uid = i_uid_into_mnt(mnt_userns, file_inode(file)),
.mode = file_inode(file)->i_mode
};
char *buffer;
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 1b0aba8eb723..7468d23c136e 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -224,7 +224,8 @@ static int common_perm(const char *op, const struct path *path, u32 mask,
*/
static int common_perm_cond(const char *op, const struct path *path, u32 mask)
{
- struct path_cond cond = { d_backing_inode(path->dentry)->i_uid,
+ struct user_namespace *mnt_userns = mnt_user_ns(path->mnt);
+ struct path_cond cond = { i_uid_into_mnt(mnt_userns, d_backing_inode(path->dentry)),
d_backing_inode(path->dentry)->i_mode
};

@@ -266,12 +267,13 @@ static int common_perm_rm(const char *op, const struct path *dir,
struct dentry *dentry, u32 mask)
{
struct inode *inode = d_backing_inode(dentry);
+ struct user_namespace *mnt_userns = mnt_user_ns(dir->mnt);
struct path_cond cond = { };

if (!inode || !path_mediated_fs(dentry))
return 0;

- cond.uid = inode->i_uid;
+ cond.uid = i_uid_into_mnt(mnt_userns, inode);
cond.mode = inode->i_mode;

return common_perm_dir_dentry(op, dir, dentry, mask, &cond);
@@ -361,11 +363,12 @@ static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_d

label = begin_current_label_crit_section();
if (!unconfined(label)) {
+ struct user_namespace *mnt_userns = mnt_user_ns(old_dir->mnt);
struct path old_path = { .mnt = old_dir->mnt,
.dentry = old_dentry };
struct path new_path = { .mnt = new_dir->mnt,
.dentry = new_dentry };
- struct path_cond cond = { d_backing_inode(old_dentry)->i_uid,
+ struct path_cond cond = { i_uid_into_mnt(mnt_userns, d_backing_inode(old_dentry)),
d_backing_inode(old_dentry)->i_mode
};

@@ -420,8 +423,9 @@ static int apparmor_file_open(struct file *file)

label = aa_get_newest_cred_label(file->f_cred);
if (!unconfined(label)) {
+ struct user_namespace *mnt_userns = file_user_ns(file);
struct inode *inode = file_inode(file);
- struct path_cond cond = { inode->i_uid, inode->i_mode };
+ struct path_cond cond = { i_uid_into_mnt(mnt_userns, inode), inode->i_mode };

error = aa_path_perm(OP_OPEN, label, &file->f_path, 0,
aa_map_file_to_perms(file), &cond);
--
2.30.0