[GIT PULL] SCSI fixes for 4.18-rc3

James Bottomley
2018-07-06T21:39:03Z

This is two minor bug fixes (aacraid, target) and a fix for a potential
exploit in the way sg handles teardown.

The patch is available here:

git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi.git scsi-fixes

The short changelog is:

David Disseldorp (1):
scsi: target: Fix truncated PR-in ReadKeys response

Jann Horn (1):
scsi: sg: mitigate read/write abuse

Raghava Aditya Renukunta (1):
scsi: aacraid: Fix PD performance regression over incorrect qd being set

And the diffstat:

drivers/scsi/aacraid/aachba.c | 15 +++++++--------
drivers/scsi/sg.c | 42 +++++++++++++++++++++++++++++++++++++++--
drivers/target/target_core_pr.c | 15 ++++++++++-----
3 files changed, 57 insertions(+), 15 deletions(-)

With full diff below.

James

---

diff --git a/drivers/scsi/aacraid/aachba.c b/drivers/scsi/aacraid/aachba.c
index a9831bd37a73..a57f3a7d4748 100644
--- a/drivers/scsi/aacraid/aachba.c
+++ b/drivers/scsi/aacraid/aachba.c
@@ -1974,7 +1974,6 @@ static void aac_set_safw_attr_all_targets(struct aac_dev *dev)
u32 lun_count, nexus;
u32 i, bus, target;
u8 expose_flag, attribs;
- u8 devtype;

lun_count = aac_get_safw_phys_lun_count(dev);

@@ -1992,23 +1991,23 @@ static void aac_set_safw_attr_all_targets(struct aac_dev *dev)
continue;

if (expose_flag != 0) {
- devtype = AAC_DEVTYPE_RAID_MEMBER;
- goto update_devtype;
+ dev->hba_map[bus][target].devtype =
+ AAC_DEVTYPE_RAID_MEMBER;
+ continue;
}

if (nexus != 0 && (attribs & 8)) {
- devtype = AAC_DEVTYPE_NATIVE_RAW;
+ dev->hba_map[bus][target].devtype =
+ AAC_DEVTYPE_NATIVE_RAW;
dev->hba_map[bus][target].rmw_nexus =
nexus;
} else
- devtype = AAC_DEVTYPE_ARC_RAW;
+ dev->hba_map[bus][target].devtype =
+ AAC_DEVTYPE_ARC_RAW;

dev->hba_map[bus][target].scan_counter = dev->scan_counter;

aac_set_safw_target_qd(dev, bus, target);
-
-update_devtype:
- dev->hba_map[bus][target].devtype = devtype;
}
}

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 53ae52dbff84..cd2fdac000c9 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -51,6 +51,7 @@ static int sg_version_num = 30536; /* 2 digits for each component */
#include <linux/atomic.h>
#include <linux/ratelimit.h>
#include <linux/uio.h>
+#include <linux/cred.h> /* for sg_check_file_access() */

#include "scsi.h"
#include <scsi/scsi_dbg.h>
@@ -209,6 +210,33 @@ static void sg_device_destroy(struct kref *kref);
sdev_prefix_printk(prefix, (sdp)->device, \
(sdp)->disk->disk_name, fmt, ##a)

+/*
+ * The SCSI interfaces that use read() and write() as an asynchronous variant of
+ * ioctl(..., SG_IO, ...) are fundamentally unsafe, since there are lots of ways
+ * to trigger read() and write() calls from various contexts with elevated
+ * privileges. This can lead to kernel memory corruption (e.g. if these
+ * interfaces are called through splice()) and privilege escalation inside
+ * userspace (e.g. if a process with access to such a device passes a file
+ * descriptor to a SUID binary as stdin/stdout/stderr).
+ *
+ * This function provides protection for the legacy API by restricting the
+ * calling context.
+ */
+static int sg_check_file_access(struct file *filp, const char *caller)
+{
+ if (filp->f_cred != current_real_cred()) {
+ pr_err_once("%s: process %d (%s) changed security contexts after opening file descriptor, this is not allowed.\n",
+ caller, task_tgid_vnr(current), current->comm);
+ return -EPERM;
+ }
+ if (uaccess_kernel()) {
+ pr_err_once("%s: process %d (%s) called from kernel context, this is not allowed.\n",
+ caller, task_tgid_vnr(current), current->comm);
+ return -EACCES;
+ }
+ return 0;
+}
+
static int sg_allow_access(struct file *filp, unsigned char *cmd)
{
struct sg_fd *sfp = filp->private_data;
@@ -393,6 +421,14 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
struct sg_header *old_hdr = NULL;
int retval = 0;

+ /*
+ * This could cause a response to be stranded. Close the associated
+ * file descriptor to free up any resources being held.
+ */
+ retval = sg_check_file_access(filp, __func__);
+ if (retval)
+ return retval;
+
if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
return -ENXIO;
SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
@@ -580,9 +616,11 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
struct sg_header old_hdr;
sg_io_hdr_t *hp;
unsigned char cmnd[SG_MAX_CDB_SIZE];
+ int retval;

- if (unlikely(uaccess_kernel()))
- return -EINVAL;
+ retval = sg_check_file_access(filp, __func__);
+ if (retval)
+ return retval;

if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
return -ENXIO;
diff --git a/drivers/target/target_core_pr.c b/drivers/target/target_core_pr.c
index 01ac306131c1..10db5656fd5d 100644
--- a/drivers/target/target_core_pr.c
+++ b/drivers/target/target_core_pr.c
@@ -3727,11 +3727,16 @@ core_scsi3_pri_read_keys(struct se_cmd *cmd)
* Check for overflow of 8byte PRI READ_KEYS payload and
* next reservation key list descriptor.
*/
- if ((add_len + 8) > (cmd->data_length - 8))
- break;
-
- put_unaligned_be64(pr_reg->pr_res_key, &buf[off]);
- off += 8;
+ if (off + 8 <= cmd->data_length) {
+ put_unaligned_be64(pr_reg->pr_res_key, &buf[off]);
+ off += 8;
+ }
+ /*
+ * SPC5r17: 6.16.2 READ KEYS service action
+ * The ADDITIONAL LENGTH field indicates the number of bytes in
+ * the Reservation key list. The contents of the ADDITIONAL
+ * LENGTH field are not altered based on the allocation length
+ */
add_len += 8;
}
spin_unlock(&dev->t10_pr.registration_lock);