need more sanity checks in blkback when using grant tables

need more sanity checks in blkback when using grant tables

[Kip Macy]

I'm upgrading FreeBSD to work against TOT in -unstable. I haven't
added grant table support to the blkfront yet. DOM0 can't cope with
this:

[XEN] Netfront recovered tx=0 rxfree=0
[XEN] Initialising virtual block device driver
(XEN) (file=grant_table.c, line=347) Bad ref (8367) or flags (2).
Unable to handle kernel paging request at virtual address dfc00008
 printing eip:
c029a01c
*pde = ma 2007d067 pa 0007d067
*pte = ma 00000000 pa 55555000
 [<c02991d6>] dispatch_probe+0x106/0x120
 [<c02990ab>] do_block_io_op+0xeb/0x110
 [<c011c09f>] daemonize+0xef/0x100
 [<c0298d57>] blkio_schedule+0x127/0x180
 [<c0116b50>] default_wake_function+0x0/0x20
 [<c01099e2>] ret_from_fork+0x6/0x1c
 [<c0116b50>] default_wake_function+0x0/0x20
 [<c0298c30>] blkio_schedule+0x0/0x180
 [<c0107ad5>] kernel_thread_helper+0x5/0x10
Oops: 0002 [#1]
PREEMPT
Modules linked in:
CPU:    0
EIP:    0061:[<c029a01c>]    Not tainted VLI
EFLAGS: 00010202   (2.6.11-xen0)
EIP is at vbd_probe_single+0xc/0x50
eax: 00000700   ebx: dfc00000   ecx: 00000155   edx: ddce2fc0
esi: 00000001   edi: daef0728   ebp: 00000155   esp: c175bef4
ds: 007b   es: 007b   ss: 0069
Process xenblkd (pid: 749, threadinfo=c175a000 task=c16900e0)
Stack: ddce2fcc c029a0b7 daef0728 dfc00000 ddce2fc0 c05f9a00 00000000 e080e008
       daef0728 c02991d6 daef0728 dfc00000 00000155 c16900e0 00000000 00000000
       ffffffff dfc00000 00000002 20af0004 fffd0002 c05f9a00 00002b0b bb9b6117
Call Trace:
 [<c029a0b7>] vbd_probe+0x57/0xb0
 [<c02991d6>] dispatch_probe+0x106/0x120
 [<c02990ab>] do_block_io_op+0xeb/0x110
 [<c011c09f>] daemonize+0xef/0x100
 [<c0298d57>] blkio_schedule+0x127/0x180
 [<c0116b50>] default_wake_function+0x0/0x20
 [<c01099e2>] ret_from_fork+0x6/0x1c
 [<c0116b50>] default_wake_function+0x0/0x20
 [<c0298c30>] blkio_schedule+0x0/0x180
 [<c0107ad5>] kernel_thread_helper+0x5/0x10
Code: 08 5b 5e 5f 5d e9 75 e2 13 00 e8 70 e2 13 00 eb b7 8d b4 26 00
00 00 00 8d bc  27 00 00 00 00 53 8b 54 24 10 8b 5c 24 0c 0f b7 02
<66> 89 43 08 0f b6 42 03 89 c1  83 c9 40 80 7a 02 00 0f 45 c1 66
 <6>note: xenblkd[749] exited with preempt_count 1

Re: need more sanity checks in blkback when using grant tables

[Christopher Clark]

Thanks for the catch, Kip. Fix inline below.

Signed-off-by: Christopher Clark


===== linux-2.6.11-xen-sparse/drivers/xen/blkback/blkback.c 1.38 vs edited =====
--- 1.38/linux-2.6.11-xen-sparse/drivers/xen/blkback/blkback.c 
2005-04-05 05:28:05 -07:00
+++ edited/linux-2.6.11-xen-sparse/drivers/xen/blkback/blkback.c   
2005-04-18 18:48:12 -07:00
@@ -397,7 +397,7 @@
                         GNTTABOP_map_grant_ref, &op, 1)))
             BUG();

-        if ( op.u.map_grant_ref.dev_bus_addr == 0 )
+        if ( op.u.map_grant_ref.handle < 0 )
             goto out;

         pending_handle(pending_idx, 0) = op.u.map_grant_ref.handle;
@@ -500,7 +500,7 @@

     for ( i = 0; i < nseg; i++ )
     {
-        if ( unlikely(aop[i].u.map_grant_ref.dev_bus_addr == 0) )
+        if ( unlikely(aop[i].u.map_grant_ref.handle < 0) )
         {
             DPRINTK("invalid buffer -- could not remap it\n");
             fast_flush_area(pending_idx, nseg);