68bd348ade
The QEMU emulation which is currently used with Raspberry PI images (qemu-system-arm -M versatilepb ...) accesses memory which was freed. Valgrind output (extract): ==17857== Invalid write of size 4 ==17857== at 0x24EB06: scsi_req_unref (scsi-bus.c:1273) ==17857== by 0x24FFAE: scsi_read_complete (scsi-disk.c:277) ==17857== by 0x152ACC: bdrv_co_em_bh (block.c:3363) ==17857== by 0x13D49C: qemu_bh_poll (async.c:71) ==17857== by 0x211A8C: main_loop_wait (main-loop.c:503) ==17857== by 0x207954: main_loop (vl.c:1555) ==17857== by 0x20E9C9: main (vl.c:3653) ==17857== Address 0x1c54383c is 12 bytes inside a block of size 260 free'd ==17857== at 0x4824B3A: free (vg_replace_malloc.c:366) ==17857== by 0x20ADFA: free_and_trace (vl.c:2250) ==17857== by 0x4899FC5: g_free (in /lib/libglib-2.0.so.0.2400.1) ==17857== by 0x24EB3B: scsi_req_unref (scsi-bus.c:1277) ==17857== by 0x24F003: scsi_req_complete (scsi-bus.c:1383) ==17857== by 0x25022A: scsi_read_data (scsi-disk.c:334) ==17857== by 0x24EB9F: scsi_req_continue (scsi-bus.c:1289) ==17857== by 0x1C7787: lsi_do_dma (lsi53c895a.c:575) ==17857== by 0x1C8CDA: lsi_execute_script (lsi53c895a.c:1147) ==17857== by 0x1C74EA: lsi_resume_script (lsi53c895a.c:510) ==17857== by 0x1C7ECD: lsi_transfer_data (lsi53c895a.c:746) ==17857== by 0x24EC90: scsi_req_data (scsi-bus.c:1307) (There are some more similar messages.) This patch adds an assertion which also detects those errors: Calling scsi_req_unref is not allowed when the previous call of that function has decremented refcount to 0, because in this case req was freed. Signed-off-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Read the documentation in qemu-doc.html or on http://wiki.qemu.org - QEMU team