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Mon, 20 Jan 2020 10:42:11 +0000 (UTC) Date: Mon, 20 Jan 2020 11:42:10 +0100 From: Kevin Wolf To: Eiichi Tsukata Subject: Re: [PATCH] block/backup: fix memory leak in bdrv_backup_top_append() Message-ID: <20200120104210.GC4970@linux.fritz.box> References: <20191223090632.30653-1-devel@etsukata.com> <221aa3d1-9e64-7fc4-e04b-dc6366978c18@virtuozzo.com> <9a335600-d9cc-bbed-7b2f-9d9d0174c7e7@etsukata.com> MIME-Version: 1.0 In-Reply-To: <9a335600-d9cc-bbed-7b2f-9d9d0174c7e7@etsukata.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: QL7ZaKBJMkuGj8tcXVcnmg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" , "qemu-block@nongnu.org" , "mreitz@redhat.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 23.12.2019 um 14:40 hat Eiichi Tsukata geschrieben: >=20 >=20 > On 2019/12/23 21:40, Vladimir Sementsov-Ogievskiy wrote: > > 23.12.2019 12:06, Eiichi Tsukata wrote: > >> bdrv_open_driver() allocates bs->opaque according to drv->instance_siz= e. > >> There is no need to allocate it and overwrite opaque in > >> bdrv_backup_top_append(). > >> > >> Reproducer: > >> > >> $ QTEST_QEMU_BINARY=3D./x86_64-softmmu/qemu-system-x86_64 valgrind = -q --leak-check=3Dfull tests/test-replication -p /replication/secondary/sta= rt > >> =3D=3D29792=3D=3D 24 bytes in 1 blocks are definitely lost in loss = record 52 of 226 > >> =3D=3D29792=3D=3D at 0x483AB1A: calloc (vg_replace_malloc.c:762) > >> =3D=3D29792=3D=3D by 0x4B07CE0: g_malloc0 (in /usr/lib64/libglib= -2.0.so.0.6000.7) > >> =3D=3D29792=3D=3D by 0x12BAB9: bdrv_open_driver (block.c:1289) > >> =3D=3D29792=3D=3D by 0x12BEA9: bdrv_new_open_driver (block.c:135= 9) > >> =3D=3D29792=3D=3D by 0x1D15CB: bdrv_backup_top_append (backup-to= p.c:190) > >> =3D=3D29792=3D=3D by 0x1CC11A: backup_job_create (backup.c:439) > >> =3D=3D29792=3D=3D by 0x1CD542: replication_start (replication.c:= 544) > >> =3D=3D29792=3D=3D by 0x1401B9: replication_start_all (replicatio= n.c:52) > >> =3D=3D29792=3D=3D by 0x128B50: test_secondary_start (test-replic= ation.c:427) > >> ... > >> > >> Fixes: 7df7868b9640 ("block: introduce backup-top filter driver") > >> Signed-off-by: Eiichi Tsukata > >> --- > >> block/backup-top.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/block/backup-top.c b/block/backup-top.c > >> index 7cdb1f8eba..617217374d 100644 > >> --- a/block/backup-top.c > >> +++ b/block/backup-top.c > >> @@ -196,7 +196,7 @@ BlockDriverState *bdrv_backup_top_append(BlockDriv= erState *source, > >> } > >> =20 > >> top->total_sectors =3D source->total_sectors; > >> - top->opaque =3D state =3D g_new0(BDRVBackupTopState, 1); > >> + state =3D top->opaque; > >> =20 > >> bdrv_ref(target); > >> state->target =3D bdrv_attach_child(top, target, "target", &chil= d_file, errp); > >> > >=20 > > Reviewed-by: Vladimir Sementsov-Ogievskiy > >=20 > > Hmm, it was not my idea, I just copied it from mirror.. And there shoul= d be the same leak. and > > may be in other places: > >=20 > > # git grep 'opaque =3D.*g_new' > > block/backup-top.c: top->opaque =3D state =3D g_new0(BDRVBackupTopSt= ate, 1); Fixed by this patch. > > block/file-posix.c: state->opaque =3D g_new0(BDRVRawReopenState, 1); > > block/gluster.c: state->opaque =3D g_new0(BDRVGlusterReopenState, 1)= ; > > block/raw-format.c: reopen_state->opaque =3D g_new0(BDRVRawState, 1)= ; > > block/sheepdog.c: re_s =3D state->opaque =3D g_new0(BDRVSheepdogReop= enState, 1); Doing this for reopen state is fine. > > block/iscsi.c: bs->opaque =3D g_new0(struct IscsiLun, 1); This one looks kind of questionable. It basically builds its BlockDriveState manually without using any of the block layer open functions. > > block/mirror.c: bs_opaque =3D g_new0(MirrorBDSOpaque, 1); Harmless as Eiichi explained below, but not nice either. > Thanks for reviewing. > As you say, block/mirror.c has similar code. But it does not cause the le= ak. > The difference is bdrv_mirror_top BlockDriver does not have .instance_siz= e > whereas bdrv_backup_top_filter BlockDriver has .instance_size =3D sizeof(= BDRVBackupTopState). > So when bdrv_open_driver() is called from mirror.c, g_malloc0(0) is > called allocating nothing. I think it should still be changed just because it would make the code cleaner. It's always better to use common infrastructure than reimplementing it locally. Kevin