The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements
Present
AT
The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required
Low
PR
The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
S
An exploited vulnerability can affect resources beyond the security scope managed by the security authority that is managing the vulnerable component. This is often referred to as a 'privilege escalation,' where the attacker can use the exploited vulnerability to gain control of resources that were not intended or authorized.
Confidentiality
Low
C
There is some impact on confidentiality, but the attacker either does not gain control of any data, or the information obtained does not have a significant impact on the system or its operations.
Integrity
Low
I
Modification of data is possible, but the attacker does not have control over what can be modified, or the extent of what the attacker can affect is limited. The data modified does not have a direct, serious impact on the system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Linux nfsd any user can set a file's ACL over NFS and grant access to itHi
David Sinquin reported that anyone may be able to grant themselves
permissions to a file by setting the ACL. nfsd did not check
permissions when setting ACLs.
CVE-2016-1237 was assigned by the Debian security team for this issue
were David Singuin initially reported the issue.
The permission checks and inode locking were lost in a refactoring
with commit 4ac7249ea5a0ceef9f8269f63f33cc873c3fac61 which was in
v3.14-rc1.
The issue is fixed with commit
999653786df6954a31044528ac3f7a5dadca08f4 in Linus' tree.
Introduced in: https://git.kernel.org/linus/4ac7249ea5a0ceef9f8269f63f33cc873c3fac61 (v3.14-rc1)
Prerequisite: https://git.kernel.org/linus/485e71e8fb6356c08c7fc6bcce4bf02c9a9a663f
Fixed by https://git.kernel.org/linus/999653786df6954a31044528ac3f7a5dadca08f4
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 8a4a266..edc452c 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -820,39 +820,43 @@ posix_acl_xattr_get(const struct xattr_handler *handler,
return error;
}
-static int
-posix_acl_xattr_set(const struct xattr_handler *handler,
- struct dentry *unused, struct inode *inode,
- const char *name, const void *value,
- size_t size, int flags)
+int
+set_posix_acl(struct inode *inode, int type, struct posix_acl *acl)
{
-struct posix_acl *acl = NULL;
-int ret;
-
if (!IS_POSIXACL(inode))
return -EOPNOTSUPP;
if (!inode->i_op->set_acl)
return -EOPNOTSUPP;
-if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
-return value ? -EACCES : 0;
+if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
+return acl ? -EACCES : 0;
if (!inode_owner_or_capable(inode))
return -EPERM;
+if (acl) {
+int ret = posix_acl_valid(acl);
+if (ret)
+return ret;
+}
+return inode->i_op->set_acl(inode, acl, type);
+}
+EXPORT_SYMBOL(set_posix_acl);
+
+static int
+posix_acl_xattr_set(const struct xattr_handler *handler,
+ struct dentry *unused, struct inode *inode,
+ const char *name, const void *value,
+ size_t size, int flags)
+{
+struct posix_acl *acl = NULL;
+int ret;
+
if (value) {
acl = posix_acl_from_xattr(&init_user_ns, value, size);
if (IS_ERR(acl))
return PTR_ERR(acl);
-
-if (acl) {
-ret = posix_acl_valid(acl);
-if (ret)
-goto out;
-}
}
-
-ret = inode->i_op->set_acl(inode, acl, handler->flags);
-out:
+ret = set_posix_acl(inode, handler->flags, acl);
posix_acl_release(acl);
return ret;
}
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