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Date: Mon, 26 Sep 2022 14:02:17 +0200 From: Michal Hocko <mhocko@...e.com> To: Florian Westphal <fw@...len.de> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, vbabka@...e.cz, akpm@...ux-foundation.org, urezki@...il.com, netdev@...r.kernel.org, netfilter-devel@...r.kernel.org, Martin Zaharinov <micron10@...il.com> Subject: Re: [PATCH mm] mm: fix BUG with kvzalloc+GFP_ATOMIC On Mon 26-09-22 12:08:00, Florian Westphal wrote: > Michal Hocko <mhocko@...e.com> wrote: > > + old_tbl = rht_dereference_rcu(ht->tbl, ht); > > + size = tbl->size; > > + > > + data = ERR_PTR(-EBUSY); > > + > > + if (rht_grow_above_75(ht, tbl)) > > + size *= 2; > > + /* Do not schedule more than one rehash */ > > + else if (old_tbl != tbl) > > + return data; > > + > > + data = ERR_PTR(-ENOMEM); > > + > > + rcu_read_unlock(); > > + new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL); > > + rcu_read_lock(); > > I don't think this is going to work, there can be callers that > rely on rcu protected data structures getting free'd. The caller of this function drops RCU for each retry, why should be the called function any special? -- Michal Hocko SUSE Labs
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