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s390x/css: handle cssid 255 correctly

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The cssid 255 is reserved but still valid from an architectural
point of view. However, feeding a bogus schid of 0xffffffff into
the virtio hypercall will lead to a crash:

Stack trace of thread 138363:
        #0  0x00000000100d168c css_find_subch (qemu-system-s390x)
        #1  0x00000000100d3290 virtio_ccw_hcall_notify
        #2  0x00000000100cbf60 s390_virtio_hypercall
        #3  0x000000001010ff7a handle_hypercall
        #4  0x0000000010079ed4 kvm_cpu_exec (qemu-system-s390x)
        #5  0x00000000100609b4 qemu_kvm_cpu_thread_fn
        #6  0x000003ff8b887bb4 start_thread (libpthread.so.0)
        #7  0x000003ff8b78df0a thread_start (libc.so.6)

This is because the css array was only allocated for 0..254
instead of 0..255.

Let's fix this by bumping MAX_CSSID to 255 and fencing off the
reserved cssid of 255 during css image allocation.

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
(cherry picked from commit 882b3b9769)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
This commit is contained in:
Cornelia Huck 2016-08-15 11:10:28 +02:00 committed by Michael Roth
parent 9ea7a46e26
commit 1b5520a3fd
2 changed files with 4 additions and 6 deletions
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8
hw/s390x/css.c
View File

@ -139,7 +139,8 @@ out_err:
int css_create_css_image(uint8_t cssid, bool default_image)
{
trace_css_new_image(cssid, default_image ? "(default)" : "");
if (cssid > MAX_CSSID) {
/* 255 is reserved */
if (cssid == 255) {
return -EINVAL;
}
if (channel_subsys.css[cssid]) {
@ -1226,7 +1227,7 @@ bool css_schid_final(int m, uint8_t cssid, uint8_t ssid, uint16_t schid)
uint8_t real_cssid;
real_cssid = (!m && (cssid == 0)) ? channel_subsys.default_cssid : cssid;
if (real_cssid > MAX_CSSID || ssid > MAX_SSID ||
if (ssid > MAX_SSID ||
!channel_subsys.css[real_cssid] ||
!channel_subsys.css[real_cssid]->sch_set[ssid]) {
return true;
@ -1241,9 +1242,6 @@ static int css_add_virtual_chpid(uint8_t cssid, uint8_t chpid, uint8_t type)
CssImage *css;
trace_css_chpid_add(cssid, chpid, type);
if (cssid > MAX_CSSID) {
return -EINVAL;
}
css = channel_subsys.css[cssid];
if (!css) {
return -EINVAL;

2
hw/s390x/css.h
View File

@ -19,7 +19,7 @@
/* Channel subsystem constants. */
#define MAX_SCHID 65535
#define MAX_SSID 3
#define MAX_CSSID 254 /* 255 is reserved */
#define MAX_CSSID 255
#define MAX_CHPID 255
#define MAX_CIWS 62