CVE-2016-4565 (published 2016-05-23T10:59Z)

The InfiniBand (aka IB) stack in the Linux kernel before 4.5.3 incorrectly relies on the write system call, which allows local users to cause a denial of service (kernel memory write operation) or possibly have unspecified other impact via a uAPI interface.

Severity: HIGH
CVSS v2 base score: 7.2 (AV:L/AC:L/Au:N/C:C/I:C/A:C)
CVSS v3 base score: 7.8, HIGH (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-264
cwe_name: Permissions, Privileges, and Access Controls
description: Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Jason Gunthorpe
author_date: 2016-04-10 19:13:13-06:00
msg: IB/security: Restrict use of the write() interface

The drivers/infiniband stack uses write() as a replacement for
bi-directional ioctl().  This is not safe. There are ways to
trigger write calls that result in the return structure that
is normally written to user space being shunted off to user
specified kernel memory instead.

For the immediate repair, detect and deny suspicious accesses to
the write API.

For long term, update the user space libraries and the kernel API
to something that doesn't present the same security vulnerabilities
(likely a structured ioctl() interface).

The impacted uAPI interfaces are generally only available if
hardware from drivers/infiniband is installed in the system.

Reported-by: Jann Horn <jann@thejh.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
[ Expanded check to all known write() entry points ]
Cc: stable@vger.kernel.org
Signed-off-by: Doug Ledford <dledford@redhat.com>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: ucm.c
change_type: ModificationType.MODIFY
diff: @@ -48,6 +48,7 @@
 
 #include <asm/uaccess.h>
 
+#include <rdma/ib.h>
 #include <rdma/ib_cm.h>
 #include <rdma/ib_user_cm.h>
 #include <rdma/ib_marshall.h>
@@ -1103,6 +1104,9 @@ static ssize_t ib_ucm_write(struct file *filp, const char __user *buf,
 	struct ib_ucm_cmd_hdr hdr;
 	ssize_t result;
 
+	if (WARN_ON_ONCE(!ib_safe_file_access(filp)))
+		return -EACCES;
+
 	if (len < sizeof(hdr))
 		return -EINVAL;
 

programming_language: C
filename: ucma.c
change_type: ModificationType.MODIFY
diff: @@ -1574,6 +1574,9 @@ static ssize_t ucma_write(struct file *filp, const char __user *buf,
 	struct rdma_ucm_cmd_hdr hdr;
 	ssize_t ret;
 
+	if (WARN_ON_ONCE(!ib_safe_file_access(filp)))
+		return -EACCES;
+
 	if (len < sizeof(hdr))
 		return -EINVAL;
 

programming_language: C
filename: uverbs_main.c
change_type: ModificationType.MODIFY
diff: @@ -48,6 +48,8 @@
 
 #include <asm/uaccess.h>
 
+#include <rdma/ib.h>
+
 #include "uverbs.h"
 
 MODULE_AUTHOR("Roland Dreier");
@@ -709,6 +711,9 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 	int srcu_key;
 	ssize_t ret;
 
+	if (WARN_ON_ONCE(!ib_safe_file_access(filp)))
+		return -EACCES;
+
 	if (count < sizeof hdr)
 		return -EINVAL;
 

programming_language: C
filename: qib_file_ops.c
change_type: ModificationType.MODIFY
diff: @@ -45,6 +45,8 @@
 #include <linux/export.h>
 #include <linux/uio.h>
 
+#include <rdma/ib.h>
+
 #include "qib.h"
 #include "qib_common.h"
 #include "qib_user_sdma.h"
@@ -2067,6 +2069,9 @@ static ssize_t qib_write(struct file *fp, const char __user *data,
 	ssize_t ret = 0;
 	void *dest;
 
+	if (WARN_ON_ONCE(!ib_safe_file_access(fp)))
+		return -EACCES;
+
 	if (count < sizeof(cmd.type)) {
 		ret = -EINVAL;
 		goto bail;

programming_language: C
filename: TODO
change_type: ModificationType.MODIFY
diff: @@ -3,4 +3,4 @@ July, 2015
 - Remove unneeded file entries in sysfs
 - Remove software processing of IB protocol and place in library for use
   by qib, ipath (if still present), hfi1, and eventually soft-roce
-
+- Replace incorrect uAPI

programming_language: Markdown
filename: file_ops.c
change_type: ModificationType.MODIFY
diff: @@ -49,6 +49,8 @@
 #include <linux/vmalloc.h>
 #include <linux/io.h>
 
+#include <rdma/ib.h>
+
 #include "hfi.h"
 #include "pio.h"
 #include "device.h"
@@ -190,6 +192,10 @@ static ssize_t hfi1_file_write(struct file *fp, const char __user *data,
 	int uctxt_required = 1;
 	int must_be_root = 0;
 
+	/* FIXME: This interface cannot continue out of staging */
+	if (WARN_ON_ONCE(!ib_safe_file_access(fp)))
+		return -EACCES;
+
 	if (count < sizeof(cmd)) {
 		ret = -EINVAL;
 		goto bail;

programming_language: C
filename: ib.h
change_type: ModificationType.MODIFY
diff: @@ -34,6 +34,7 @@
 #define _RDMA_IB_H
 
 #include <linux/types.h>
+#include <linux/sched.h>
 
 struct ib_addr {
 	union {
@@ -86,4 +87,19 @@ struct sockaddr_ib {
 	__u64			sib_scope_id;
 };
 
+/*
+ * The IB interfaces that use write() as bi-directional ioctl() are
+ * fundamentally unsafe, since there are lots of ways to trigger "write()"
+ * calls from various contexts with elevated privileges. That includes the
+ * traditional suid executable error message writes, but also various kernel
+ * interfaces that can write to file descriptors.
+ *
+ * This function provides protection for the legacy API by restricting the
+ * calling context.
+ */
+static inline bool ib_safe_file_access(struct file *filp)
+{
+	return filp->f_cred == current_cred() && segment_eq(get_fs(), USER_DS);
+}
+
 #endif /* _RDMA_IB_H */

programming_language: C