Re: [PATCH] block-migration: Ensure we don't crash during migration cleanup

[Claudio Fontana <cfontana@suse.de>]

On 8/8/23 19:08, Stefan Hajnoczi wrote:
> On Mon, Jul 31, 2023 at 05:33:38PM -0300, Fabiano Rosas wrote:
>> 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
>>
>> Signed-off-by: Fabiano Rosas <farosas@suse.de>
>> ---
>>  migration/block.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> Sorry, I missed this patch!
> 
> If this needs to be in QEMU 8.1 (-rc3 is being tagged today), please
> reply and provide a justification. At this point only security fixes and
> showstoppers will be merged. Thanks!
> 
> Applied to my block-next tree for QEMU 8.2:
> https://gitlab.com/stefanha/qemu/commits/block-next
> 
> Stefan

Thanks, and in my personal view I think it's ok for 8.2, IIUC it happens during the migration to file work which is not in 8.1 anyway,
Fabiano correct me here if I am wrong,

Ciao,

Claudio