Commit 1bca7359 authored Aug 29, 2025 by Pasha Tatashin Committed by Andrew Morton Sep 21, 2025

fork: check charging success before zeroing stack

Patch series "mm: task_stack: Stack handling cleanups".

These are some small cleanups for the fork code that was split off from
Pasha:s dynamic stack patch series, they are generally nice on their own
so let's propose them for merging.


This patch (of 2):

No need to do zero cached stack if memcg charge fails, so move the
charging attempt before the memset operation.

Link: https://lkml.kernel.org/r/20250829-fork-cleanups-for-dynstack-v1-0-3bbaadce1f00@linaro.org
Link: https://lkml.kernel.org/r/20250829-fork-cleanups-for-dynstack-v1-1-3bbaadce1f00@linaro.org


Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/20240311164638.2015063-6-pasha.tatashin@soleen.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Ben Segall <bsegall@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Mel Gorman <mgorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 4dfd4bba

kernel/fork.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -290,6 +290,11 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node)
		if (!vm_area)
		continue;

		if (memcg_charge_kernel_stack(vm_area)) {
		vfree(vm_area->addr);
		return -ENOMEM;
		}

		/* Reset stack metadata. */
		kasan_unpoison_range(vm_area->addr, THREAD_SIZE);

		@@ -298,11 +303,6 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node)
		/* Clear stale pointers from reused stack. */
		memset(stack, 0, THREAD_SIZE);

		if (memcg_charge_kernel_stack(vm_area)) {
		vfree(vm_area->addr);
		return -ENOMEM;
		}

		tsk->stack_vm_area = vm_area;
		tsk->stack = stack;
		return 0;