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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?X2vUHiWAqIbGazF7urX7lPM3M/N1PMQqr4AkICuDNaK0dwK818vYM0aVwX/z?= =?us-ascii?Q?EOoTYinnBUE+820uPugpSNfF+5pMoHAjRc9dyA2LW+w/sLL4HD1lVERUP4gb?= =?us-ascii?Q?Jxjl4BvO6h6tctvvHBJFDSoYZu4PKTnyjhvk9uL9wkO0PE7i2iXK9eJTPHoL?= =?us-ascii?Q?bg+cAdYxXSI+1hxOHIvnI5cCKvxs8vsz3W/ENV+qX2LTEtCS/qMTcFS7qJKx?= =?us-ascii?Q?i9DIIMq6WDxXEMuP8JaME91n2vq6eIXED2pcgiyNyl9UKl8h8/JZyJMmNos8?= =?us-ascii?Q?lj/2oRFe1blWWwmtHqeAf7WkcaJXgmieqzVSaeYlFtfcFsoo9VBOQesS3d5Y?= =?us-ascii?Q?6jc/PEt5Lxn92vFQO8ORWTSh08Otl9ZvRvUSzD+mJZqyBumzr3/iprPaqa93?= =?us-ascii?Q?VcRNqf1mjvcGzItOZUnkP4UVgr6BqNA6Q1DQlX7KvQUIUqYD7fZcEORm7gEq?= =?us-ascii?Q?Q9SXkdPyIvoyg9avtwAatL79zS564ZG+BbaIoDEtixvZKbgdhhRDlz2F6bZ5?= =?us-ascii?Q?y4pCDC5adT+1bfO7CNWXy3tTbuKIN/jPwEJ8KR1mHBIE57r+qXW9CMcGv3Ng?= =?us-ascii?Q?PcUxuXva6xS5s1+VKa8Q9Xed9F68GoTrTPagwj649idNeUeW8pixeAUCzzkD?= =?us-ascii?Q?H7U5sg+V3pFRxW+etFHCQTO9Yg1gdLsLDCl87USIUPvvqnV7GalsFqfAN/sW?= =?us-ascii?Q?J5ElE2OhZU3l5XIP7PD1mVXLo00FPbzYmytq5JGWq+Iz3h+ICAZM2k6f7M4b?= =?us-ascii?Q?GUtESrqAHTcuNaX8/mwQac/t+gDzwf7o5nFS9OFCb/q0835uATgf7jjgBK7A?= =?us-ascii?Q?WXqbS5BB4nfP7+dgXwLeqRFgxcr5kaDkqgxebmprvAPvaoN1GcCMlAstoUlu?= =?us-ascii?Q?zAm1elLTi3nt7JPnO4z6i+PTTWo9a5ELFgndmtbDc5tNA5e8+6VlIRbQPCoz?= =?us-ascii?Q?biuEVF3AU+GShjP7+otMdZHaWhNvMR9pk9PN8iJoXn1HDZajoylkaNidxy7K?= =?us-ascii?Q?jRT2doAeLPAMo1kjjJcFj9P929NdG0KcICvdXq5N992ndq1lw9tdg1lUTsib?= =?us-ascii?Q?bRxd2YuEj2PVenQb2WNapOb946WVxlR0rmNPYyMQVp8/STB1P2HHna7Hyh3d?= =?us-ascii?Q?E5V5MVMz63THnCUz/KYg2VAM+cL2K8TqmzmRMfQTXTEFC+Tb59HflkQ7Y6Gu?= =?us-ascii?Q?FgBgAr2Qss+akT1T2jby3Q7VfCNl7jIySyMPzU+KcaS70pxy+HogMKfT2ss3?= =?us-ascii?Q?4nEyvAWBdMQckn/ydGtu78tzEz497QQVoMHgIYZ5luVm6kd/0smuhpXKjxXN?= =?us-ascii?Q?ar1ECbcDfZi8AVbm5+QsiRvsKJzzPgO6V5jxJDKAXoEnjw=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 0dfb1f56-770d-43f1-bc03-08d8ed5ebbcd X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Mar 2021 18:17:20.8385 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 4g6xAh7zcGAlJM7lhI9V+rb4+GyIzyG06PQ+7tXxZqwiQBTa0bancHOeZ75JQj2A X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR15MB4153 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-03-22_10:2021-03-22,2021-03-22 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 impostorscore=0 clxscore=1015 lowpriorityscore=0 mlxlogscore=652 mlxscore=0 bulkscore=0 suspectscore=0 priorityscore=1501 malwarescore=0 adultscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2103220133 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 20, 2021 at 12:38:14AM +0800, Muchun Song wrote: > The rcu_read_lock/unlock only can guarantee that the memcg will not be > freed, but it cannot guarantee the success of css_get (which is in the > refill_stock when cached memcg changed) to memcg. > > rcu_read_lock() > memcg = obj_cgroup_memcg(old) > __memcg_kmem_uncharge(memcg) > refill_stock(memcg) > if (stock->cached != memcg) > // css_get can change the ref counter from 0 back to 1. > css_get(&memcg->css) > rcu_read_unlock() > > This fix is very like the commit: > > eefbfa7fd678 ("mm: memcg/slab: fix use after free in obj_cgroup_charge") > > Fix this by holding a reference to the memcg which is passed to the > __memcg_kmem_uncharge() before calling __memcg_kmem_uncharge(). > > Fixes: 3de7d4f25a74 ("mm: memcg/slab: optimize objcg stock draining") > Signed-off-by: Muchun Song Acked-by: Roman Gushchin Thanks!