Re: [PULL v3 1/5] block-migration: Ensure we don't crash during migration cleanup

[Fabiano Rosas <farosas@suse.de>]

Michael Tokarev <mjt@tls.msk.ru> writes:

> 30.08.2023 14:49, Stefan Hajnoczi wrote:
>> From: Fabiano Rosas <farosas@suse.de>
>> 
>> We can fail the blk_insert_bs() at init_blk_migration(), leaving the
>> BlkMigDevState without a dirty_bitmap and BlockDriverState. Account
>> for the possibly missing elements when doing cleanup.
>> 
>> Fix the following crashes:
>> 
>> Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
>> 0x0000555555ec83ef in bdrv_release_dirty_bitmap (bitmap=0x0) at ../block/dirty-bitmap.c:359
>> 359         BlockDriverState *bs = bitmap->bs;
>>   #0  0x0000555555ec83ef in bdrv_release_dirty_bitmap (bitmap=0x0) at ../block/dirty-bitmap.c:359
>>   #1  0x0000555555bba331 in unset_dirty_tracking () at ../migration/block.c:371
>>   #2  0x0000555555bbad98 in block_migration_cleanup_bmds () at ../migration/block.c:681
>> 
>> Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
>> 0x0000555555e971ff in bdrv_op_unblock (bs=0x0, op=BLOCK_OP_TYPE_BACKUP_SOURCE, reason=0x0) at ../block.c:7073
>> 7073        QLIST_FOREACH_SAFE(blocker, &bs->op_blockers[op], list, next) {
>>   #0  0x0000555555e971ff in bdrv_op_unblock (bs=0x0, op=BLOCK_OP_TYPE_BACKUP_SOURCE, reason=0x0) at ../block.c:7073
>>   #1  0x0000555555e9734a in bdrv_op_unblock_all (bs=0x0, reason=0x0) at ../block.c:7095
>>   #2  0x0000555555bbae13 in block_migration_cleanup_bmds () at ../migration/block.c:690
>
> This smells like -stable material, is it not?
> (applies to 7.2, 8.0 and 8.1).

Yes, I agree.