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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PAXPR04MB8459.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: ec3799a0-e315-48d1-a479-08dcc70b44c1 X-MS-Exchange-CrossTenant-originalarrivaltime: 28 Aug 2024 02:43:59.1679 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 1KAoCPubbgSwsZCSMZPixxJo8UORi317BgF54LI/k+hMwfgoHCtAYHT8jG4tiDaWgApexhQFis6/aGXry0T8oA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PA4PR04MB7856 X-Stat-Signature: u19skcqrjy618fkhy73ardomk1fh7e4n X-Rspamd-Queue-Id: 10AC51C0009 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1724813046-75738 X-HE-Meta: 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 PH2lLwHh 0FpkbZprngD++yQIfEvYxqIdbN4mkpAID82wvs1gXNTWaYSnp90mKa5WYpF7bSgPElO7mMmJlcId5PZgpKZSdjBAA1LGT03/gD0+rP1/yNKkdes8hPywOGzweClIUkL3WnL9FvOlgD2sBdYX3B7KOtieaw/wZCTak8bCN0fL3HWEvm7PUs7E86eOSZLD5mXjpHcXvd4MWvZJdIf2tv3SbPUmTZHQTkH/BryQvn6VwryI3xm2+fxpennxulUIiMVSR2+XZX48dr25bn/C8jWKAIa0YUbNsNQaHP60wxQ4gY/0ky+M6EBAsFXW/uga2L9wfLnnvH9Bu+FL07nyPr7WQbT1yjyBUr0fSYh121fyiEz/9VRdfUUgHItmzGjz7yEivNwBOhZ6h1Q0bX2HHlIHU5dD5j/NaReW/HjUiOMuFzXFuB3lFP985dkTPAfpiynun9egPUI4cQOZF0QHRvycUqLg7SIMvOfQLYDhm X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > Subject: Re: [PATCH V1] mm, slub: avoid zeroing kmalloc redzone >=20 > On Fri, Aug 23, 2024 at 02:24:15PM +0800, Peng Fan (OSS) wrote: > > From: Peng Fan > > > > With commit 946fa0dbf2d8 > > ("mm/slub: extend redzone check to extra allocated kmalloc space > than > > requested"), setting orig_size treats the wasted space (object_size - > > orig_size) as redzones. But (in check_object()) when orig_size is set > > to zero, the entire object is perceived as a redzone. To a valid > > allocated kmalloc space, when init_on_free=3D1, the wasted space and > the > > orig_size should not be cleared to 0, otherwise there will be kernel > dump: > > > > [ 0.000000] > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > [ 0.000000] BUG kmalloc-8 (Not tainted): kmalloc Redzone > overwritten > > [ 0.000000] --------------------------------------------------------= --------------------- > > [ 0.000000] > > [ 0.000000] 0xffff000010032858-0xffff00001003285f > @offset=3D2136. First byte 0x0 instead of 0xcc > > [ 0.000000] FIX kmalloc-8: Restoring kmalloc Redzone > 0xffff000010032858-0xffff00001003285f=3D0xcc > > [ 0.000000] Slab 0xfffffdffc0400c80 objects=3D36 used=3D23 > fp=3D0xffff000010032a18 > flags=3D0x3fffe0000000200(workingset|node=3D0|zone=3D0|lastcpupid=3D0x1f > fff) > > [ 0.000000] Object 0xffff000010032858 @offset=3D2136 > fp=3D0xffff0000100328c8 > > [ 0.000000] > > [ 0.000000] Redzone ffff000010032850: cc cc cc cc cc cc cc > cc ........ > > [ 0.000000] Object ffff000010032858: cc cc cc cc cc cc cc > cc ........ > > [ 0.000000] Redzone ffff000010032860: cc cc cc cc cc cc cc > cc ........ > > [ 0.000000] Padding ffff0000100328b4: 00 00 00 00 00 00 00 00 > 00 00 00 00 ............ > > [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted > 6.11.0-rc3-next-20240814-00004-g61844c55c3f4 #144 > > [ 0.000000] Hardware name: NXP i.MX95 19X19 board (DT) > > [ 0.000000] Call trace: > > [ 0.000000] dump_backtrace+0x90/0xe8 > > [ 0.000000] show_stack+0x18/0x24 > > [ 0.000000] dump_stack_lvl+0x74/0x8c > > [ 0.000000] dump_stack+0x18/0x24 > > [ 0.000000] print_trailer+0x150/0x218 > > [ 0.000000] check_object+0xe4/0x454 > > [ 0.000000] free_to_partial_list+0x2f8/0x5ec > > > > To address the issue, use orig_size to clear the used area. And > > restore the value of orig_size after clear the remaining area. > > > > When CONFIG_SLUB_DEBUG not defined, (get_orig_size()' directly > returns > > s->object_size. So when using memset to init the area, the size can > > s->simply > > be orig_size, as orig_size returns object_size when > CONFIG_SLUB_DEBUG > > not enabled. And orig_size can never be bigger than object_size. > > > > Fixes: 946fa0dbf2d8 ("mm/slub: extend redzone check to extra > allocated > > kmalloc space than requested") >=20 > Thanks for the fix! I missed to test the 'init_on_free' case back then. >=20 > Reviewed-by: Feng Tang >=20 > with one small nit below >=20 > > Signed-off-by: Peng Fan > > --- > > > > RFC->V1: > > Update commit log (Per Hyeonggon) > > Use orig_size to do memset(Per Hyeonggon) Add get_orig_size and > > set_orig_size when CONFIG_SLUB_DEBUG not enabled(kernel test > robot) > > > > > > > > mm/slub.c | 20 ++++++++++++++++++-- > > 1 file changed, 18 insertions(+), 2 deletions(-) > > > > diff --git a/mm/slub.c b/mm/slub.c > > index 94f5a4143825..a5fbeb2835b1 100644 > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -1895,6 +1895,15 @@ static inline void inc_slabs_node(struct > > kmem_cache *s, int node, static inline void dec_slabs_node(struct > kmem_cache *s, int node, > > int objects) > {} > > > > +static inline unsigned int get_orig_size(struct kmem_cache *s, void > > +*object) { > > + return s->object_size; > > +} > > + > > +static inline void set_orig_size(struct kmem_cache *s, void *object, > > + unsigned int orig_size) > > +{} >=20 > Current get_orig_size() and set_orig_size() are protected by > CONFIG_SLUB_DEUG=3Dy macro, and with this patch, they will be called > in both ON and OFF case. Maybe we can just lift those existing > functions out of the "#ifdef CONFIG_SLUB_DEBUG" protection? This will build a bit more code when CONFIG_SLUB_DEBUG is not defined. But it should be fine. I will wait to see if other people have comments on this. Thanks, Peng. >=20 > Thanks, > Feng