| Message ID | 20230330133822.66271-1-mathieu.desnoyers@efficios.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/1] mm: Fix memory leak on mm_init error handling | expand |
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
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:
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(+)