[4.2.y-ckt stable] Patch "IB/security: Restrict use of the write() interface" has been added to the 4.2.y-ckt tree
Kamal Mostafa
kamal at canonical.com
Mon May 9 19:43:50 UTC 2016
This is a note to let you know that I have just added a patch titled
IB/security: Restrict use of the write() interface
to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree
which can be found at:
https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue
This patch is scheduled to be released in version 4.2.8-ckt10.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
---8<------------------------------------------------------------
>From 26755d09ce0ca30d8055a0676ccab83050ac0f18 Mon Sep 17 00:00:00 2001
From: Jason Gunthorpe <jgunthorpe at obsidianresearch.com>
Date: Sun, 10 Apr 2016 19:13:13 -0600
Subject: IB/security: Restrict use of the write() interface
commit e6bd18f57aad1a2d1ef40e646d03ed0f2515c9e3 upstream.
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 at thejh.net>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Jason Gunthorpe <jgunthorpe at obsidianresearch.com>
[ Expanded check to all known write() entry points ]
Signed-off-by: Doug Ledford <dledford at redhat.com>
[ kamal: backport to 4.2-stable: no staging/rdma/ ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
drivers/infiniband/core/ucm.c | 4 ++++
drivers/infiniband/core/ucma.c | 3 +++
drivers/infiniband/core/uverbs_main.c | 5 +++++
drivers/infiniband/hw/qib/qib_file_ops.c | 5 +++++
include/rdma/ib.h | 16 ++++++++++++++++
5 files changed, 33 insertions(+)
diff --git a/drivers/infiniband/core/ucm.c b/drivers/infiniband/core/ucm.c
index 0094810..aca6043 100644
--- a/drivers/infiniband/core/ucm.c
+++ b/drivers/infiniband/core/ucm.c
@@ -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>
@@ -1104,6 +1105,9 @@ 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;
diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 29b2121..66f1ca8 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -1474,6 +1474,9 @@ 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;
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 15f4126..77c04a3 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -48,6 +48,8 @@
#include <asm/uaccess.h>
+#include <rdma/ib.h>
+
#include "uverbs.h"
MODULE_AUTHOR("Roland Dreier");
@@ -614,6 +616,9 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
struct ib_uverbs_cmd_hdr hdr;
__u32 flags;
+ if (WARN_ON_ONCE(!ib_safe_file_access(filp)))
+ return -EACCES;
+
if (count < sizeof hdr)
return -EINVAL;
diff --git a/drivers/infiniband/hw/qib/qib_file_ops.c b/drivers/infiniband/hw/qib/qib_file_ops.c
index 7258818..619154e 100644
--- a/drivers/infiniband/hw/qib/qib_file_ops.c
+++ b/drivers/infiniband/hw/qib/qib_file_ops.c
@@ -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;
diff --git a/include/rdma/ib.h b/include/rdma/ib.h
index cf8f9e7..a6b9370 100644
--- a/include/rdma/ib.h
+++ b/include/rdma/ib.h
@@ -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 */
--
2.7.4
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