commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") introduces a memory leak by missing a call to destroy_context() when a percpu_counter fails to allocate.
Before introducing the per-cpu counter allocations, init_new_context() was the last call that could fail in mm_init(), and thus there was no need to ever invoke destroy_context() in the error paths. Adding the following percpu counter allocations adds error paths after init_new_context(), which means its associated destroy_context() needs to be called when percpu counters fail to allocate.
Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Shakeel Butt shakeelb@google.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Marek Szyprowski m.szyprowski@samsung.com Cc: linux-mm@kvack.org Cc: stable@vger.kernel.org # 6.2 --- kernel/fork.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/fork.c b/kernel/fork.c index c0257cbee093..c983c4fe3090 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1171,6 +1171,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, fail_pcpu: while (i > 0) percpu_counter_destroy(&mm->rss_stat[--i]); + destroy_context(mm); fail_nocontext: mm_free_pgd(mm); fail_nopgd:
On Thu, Mar 30, 2023 at 09:38:22AM -0400, Mathieu Desnoyers wrote:
commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") introduces a memory leak by missing a call to destroy_context() when a percpu_counter fails to allocate.
Before introducing the per-cpu counter allocations, init_new_context() was the last call that could fail in mm_init(), and thus there was no need to ever invoke destroy_context() in the error paths. Adding the following percpu counter allocations adds error paths after init_new_context(), which means its associated destroy_context() needs to be called when percpu counters fail to allocate.
Fixes: f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter")
Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Shakeel Butt shakeelb@google.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Marek Szyprowski m.szyprowski@samsung.com Cc: linux-mm@kvack.org Cc: stable@vger.kernel.org # 6.2
Acked-by: Shakeel Butt shakeelb@google.com
On Thu, 30 Mar 2023 09:38:22 -0400 Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") introduces a memory leak by missing a call to destroy_context() when a percpu_counter fails to allocate.
Before introducing the per-cpu counter allocations, init_new_context() was the last call that could fail in mm_init(), and thus there was no need to ever invoke destroy_context() in the error paths. Adding the following percpu counter allocations adds error paths after init_new_context(), which means its associated destroy_context() needs to be called when percpu counters fail to allocate.
...
--- a/kernel/fork.c +++ b/kernel/fork.c @@ -1171,6 +1171,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, fail_pcpu: while (i > 0) percpu_counter_destroy(&mm->rss_stat[--i]);
- destroy_context(mm);
fail_nocontext: mm_free_pgd(mm); fail_nopgd:
Is there really a leak? I wasn't able to find a version of init_new_context() which performs allocation.
On Thu, Mar 30, 2023 at 12:42 PM Andrew Morton akpm@linux-foundation.org wrote:
On Thu, 30 Mar 2023 09:38:22 -0400 Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") introduces a memory leak by missing a call to destroy_context() when a percpu_counter fails to allocate.
Before introducing the per-cpu counter allocations, init_new_context() was the last call that could fail in mm_init(), and thus there was no need to ever invoke destroy_context() in the error paths. Adding the following percpu counter allocations adds error paths after init_new_context(), which means its associated destroy_context() needs to be called when percpu counters fail to allocate.
...
--- a/kernel/fork.c +++ b/kernel/fork.c @@ -1171,6 +1171,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, fail_pcpu: while (i > 0) percpu_counter_destroy(&mm->rss_stat[--i]);
destroy_context(mm);fail_nocontext: mm_free_pgd(mm); fail_nopgd:
Is there really a leak? I wasn't able to find a version of init_new_context() which performs allocation.
There are more than 20 archs defining this function and I couldn't check each one of them. I think we can assume there might be new allocation in the future.
On 2023-03-30 15:42, Andrew Morton wrote:
On Thu, 30 Mar 2023 09:38:22 -0400 Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") introduces a memory leak by missing a call to destroy_context() when a percpu_counter fails to allocate.
Before introducing the per-cpu counter allocations, init_new_context() was the last call that could fail in mm_init(), and thus there was no need to ever invoke destroy_context() in the error paths. Adding the following percpu counter allocations adds error paths after init_new_context(), which means its associated destroy_context() needs to be called when percpu counters fail to allocate.
...
--- a/kernel/fork.c +++ b/kernel/fork.c @@ -1171,6 +1171,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, fail_pcpu: while (i > 0) percpu_counter_destroy(&mm->rss_stat[--i]);
- destroy_context(mm); fail_nocontext: mm_free_pgd(mm); fail_nopgd:
Is there really a leak? I wasn't able to find a version of init_new_context() which performs allocation.
AFAIU, at least on powerpc:
arch/powerpc/mm/book3s64/mmu_context.c: init_new_context() calls radix__init_new_context() or hash__init_new_context() which leak IDs through ida_alloc_range.
Thanks,
Mathieu
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