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b=bDgHPV32AfnOA8tw27tWvIXqOB1SK0Mw1obz6QAL91FB2/8WIiMsDeDPTFHflGYUO Xxl+HpJeRej3CgZYBbGb16a82nK3zijlC81Owhxp5XPLUfPbPqQv+TXDnMpGPN7Rdg acW+rs3XGOZ9cUEr//0lg7VzCTCiAE9zWoBZeBwHyl8LhZ7hFkC3CjGDKyMnzP0T6m Nd8I44uarM0v19lVNo9c+B1+rDl4uJGAJnTA3P+soFHqiQig6NsUavR7C+sFNCadZ6 vdL01HrPpO7S7FdmiNm153lHhg1cITFA2OT7wtFGnbfd5pDQsu7mtowRMdCFXQgV39 pURQxKVwWgMpg== Date: Wed, 1 Jul 2026 09:38:57 +0300 From: Mike Rapoport To: Gregory Price Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, kernel-team@meta.com, david@kernel.org, osalvador@suse.de, akpm@linux-foundation.org, mgorman@techsingularity.net, hannes@cmpxchg.org, vbabka@kernel.org Subject: Re: [PATCH] mm/mm_init: handle alloc_percpu failure in free_area_init_core_hotplug Message-ID: References: <20260630214039.2263562-1-gourry@gourry.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260630214039.2263562-1-gourry@gourry.net> X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E000640008 X-Stat-Signature: g4izjcb3q4hhnzjyohpycptznxrkptod X-HE-Tag: 1782887945-915053 X-HE-Meta: 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 JWaw8ddb 7h5u5N0FkPxRA0uNneD9Rt/oPkcZUErwTbx4SjzUCwTfZeZaOgvXWL1habqYSpXDjl4SDpHuRmn00aDUY1q1VeM5QgdesWd94tZ0hh3CqenrcZ8r7geHXNyOVfmA682yor9QPTUiDi5Rxz+Zd59wwWUqmH+cTze9hFfUuY8Ozf5P1vFDSuzvKjAz1ktgF2d0HMvorkBnY0Wz17Th21M6Mx1vCKGh8jh6pCuReKY21p5frSo84yxGiC7zEsjKTNejNcz/VTU2/2OfpZO5mSobA1OubfNPdXkTwOs9FYGBvIAm00Tsp/H41TGh5hUFIEf8YhwoPURZWOAGJbu8Oh47FmjAVkU0GkzOS9iKwe3frgihNqZC/OkkykWJjsOroP6GFL1P6 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 30, 2026 at 05:40:39PM -0400, Gregory Price wrote: > We miss a failed allocation check for pgdat->per_cpu_nodestats, which > results in a NULL deref when we offset into the per-cpu area. > > Propagate -ENOMEM up the stack and leave per_cpu_nodestats pointing > at boot_nodestats so a later online can retry the allocation. > > hotadd_init_pgdat() returns NULL on failure, which __try_online_node() > already maps to -ENOMEM. > > Assisted-by: Sashiko:unknown-model I suppose it's rather Reported-by: Sashiko > Fixes: 75ef71840539 ("mm, vmstat: add infrastructure for per-node vmstats") > Signed-off-by: Gregory Price > --- > include/linux/memory_hotplug.h | 2 +- > mm/memory_hotplug.c | 3 ++- > mm/mm_init.c | 14 +++++++++++--- > 3 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h > index 7c9d66729c60..f04b915678db 100644 > --- a/include/linux/memory_hotplug.h > +++ b/include/linux/memory_hotplug.h > @@ -289,7 +289,7 @@ static inline void __remove_memory(u64 start, u64 size) {} > /* Default online_type (MMOP_*) when new memory blocks are added. */ > extern enum mmop mhp_get_default_online_type(void); > extern void mhp_set_default_online_type(enum mmop online_type); > -extern void __ref free_area_init_core_hotplug(struct pglist_data *pgdat); > +extern int __ref free_area_init_core_hotplug(struct pglist_data *pgdat); Nit: we are trying to get rid of 'extern's in the headers, even though it makes the declarations inconsistent. Can you please drop the extern since you anyway changing this? > extern int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags); > extern int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags); > extern int add_memory_resource(int nid, struct resource *resource, > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 7ac19fab2263..8b137328dcf0 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1263,7 +1263,8 @@ static pg_data_t *hotadd_init_pgdat(int nid) > pgdat = NODE_DATA(nid); > > /* init node's zones as empty zones, we don't have any present pages.*/ > - free_area_init_core_hotplug(pgdat); > + if (free_area_init_core_hotplug(pgdat)) > + return NULL; > > /* > * The node we allocated has no zone fallback lists. For avoiding > diff --git a/mm/mm_init.c b/mm/mm_init.c > index 306ea5c13f54..37fd64ce144d 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -1536,7 +1536,7 @@ void __init set_pageblock_order(void) > * NOTE: this function is only called during memory hotplug > */ > #ifdef CONFIG_MEMORY_HOTPLUG > -void __ref free_area_init_core_hotplug(struct pglist_data *pgdat) > +int __ref free_area_init_core_hotplug(struct pglist_data *pgdat) > { > int nid = pgdat->node_id; > enum zone_type z; > @@ -1544,8 +1544,14 @@ void __ref free_area_init_core_hotplug(struct pglist_data *pgdat) > > pgdat_init_internals(pgdat); > > - if (pgdat->per_cpu_nodestats == &boot_nodestats) > - pgdat->per_cpu_nodestats = alloc_percpu(struct per_cpu_nodestat); > + if (pgdat->per_cpu_nodestats == &boot_nodestats) { > + struct per_cpu_nodestat __percpu *p; > + > + p = alloc_percpu(struct per_cpu_nodestat); > + if (!p) > + return -ENOMEM; > + pgdat->per_cpu_nodestats = p; > + } > > /* > * Reset the nr_zones, order and highest_zoneidx before reuse. > @@ -1583,6 +1589,8 @@ void __ref free_area_init_core_hotplug(struct pglist_data *pgdat) > zone->present_pages = 0; > zone_init_internals(zone, z, nid, 0); > } > + > + return 0; > } > #endif > > -- > 2.53.0-Meta > -- Sincerely yours, Mike.