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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: bb527c95-7873-4b64-e829-08d6f4691a72 X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Jun 2019 03:49:17.0726 (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: guro@fb.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR15MB2794 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-19_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906190029 X-FB-Internal: deliver 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: Acked-by: Roman Gushchin Thank you, Andrea! > On Jun 18, 2019, at 18:15, Andrea Arcangeli wrote: >=20 > Commit 5eed6f1dff87bfb5e545935def3843edf42800f2 corrected two > instances, but there was a third instance of this bug. >=20 > Without setting tsk->stack, if memcg_charge_kernel_stack fails, it'll > execute free_thread_stack() on a dangling pointer. >=20 > Enterprise kernels are compiled with VMAP_STACK=3Dy so this isn't > critical, but custom VMAP_STACK=3Dn builds should have some performance > advantage, with the drawback of risking to fail fork because > compaction didn't succeed. So as long as VMAP_STACK=3Dn is a supported > option it's worth fixing it upstream. >=20 > Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") > Signed-off-by: Andrea Arcangeli > --- > kernel/fork.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) >=20 > diff --git a/kernel/fork.c b/kernel/fork.c > index d6c324b1b29e..9ee28dfe7c21 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -248,7 +248,11 @@ static unsigned long *alloc_thread_stack_node(struct= task_struct *tsk, int node) > struct page *page =3D alloc_pages_node(node, THREADINFO_GFP, > THREAD_SIZE_ORDER); >=20 > - return page ? page_address(page) : NULL; > + if (likely(page)) { > + tsk->stack =3D page_address(page); > + return tsk->stack; > + } > + return NULL; > #endif > } >=20 >=20