[PATCH v1 1/9] landlock: Fix memory allocation error handling

From: Mickaël Salaün
Date: Wed Nov 11 2020 - 16:34:54 EST


Handle memory allocation errors in landlock_create_object() call. This
prevent to inadvertently hold an inode. Also, make get_inode_object()
more readable.

Cc: James Morris <jmorris@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Serge E. Hallyn <serge@xxxxxxxxxx>
Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
---
security/landlock/fs.c | 5 +++++
security/landlock/object.c | 5 +++--
2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index d8c5d19ac2af..b67c821bb40b 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -9,6 +9,7 @@
#include <linux/atomic.h>
#include <linux/compiler_types.h>
#include <linux/dcache.h>
+#include <linux/err.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
@@ -98,6 +99,8 @@ static struct landlock_object *get_inode_object(struct inode *const inode)
* holding any locks).
*/
new_object = landlock_create_object(&landlock_fs_underops, inode);
+ if (IS_ERR(new_object))
+ return new_object;

spin_lock(&inode->i_lock);
object = rcu_dereference_protected(inode_sec->object,
@@ -145,6 +148,8 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
access_rights |= _LANDLOCK_ACCESS_FS_MASK & ~ruleset->fs_access_mask;
rule.access = access_rights;
rule.object = get_inode_object(d_backing_inode(path->dentry));
+ if (IS_ERR(rule.object))
+ return PTR_ERR(rule.object);
mutex_lock(&ruleset->lock);
err = landlock_insert_rule(ruleset, &rule, false);
mutex_unlock(&ruleset->lock);
diff --git a/security/landlock/object.c b/security/landlock/object.c
index a71644ee72a7..54ba0327002a 100644
--- a/security/landlock/object.c
+++ b/security/landlock/object.c
@@ -8,6 +8,7 @@

#include <linux/bug.h>
#include <linux/compiler_types.h>
+#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/rcupdate.h>
#include <linux/refcount.h>
@@ -23,10 +24,10 @@ struct landlock_object *landlock_create_object(
struct landlock_object *new_object;

if (WARN_ON_ONCE(!underops || !underobj))
- return NULL;
+ return ERR_PTR(-ENOENT);
new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT);
if (!new_object)
- return NULL;
+ return ERR_PTR(-ENOMEM);
refcount_set(&new_object->usage, 1);
spin_lock_init(&new_object->lock);
new_object->underops = underops;
--
2.29.2