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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>
This commit is contained in:
Cornelia Huck 2016-08-15 11:10:28 +02:00
parent 5759db1936
commit 882b3b9769
2 changed files with 4 additions and 6 deletions
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2
include/hw/s390x/css.h
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@ -20,7 +20,7 @@
#define MAX_DEVNO 65535
#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