On Thu, Nov 03, 2022 at 09:33:28AM +0100, Vlastimil Babka wrote:
[...]
> >> AFAICS before this patch, we "survive" "kmem_cache *s" being NULL as
> >> slab_pre_alloc_hook() will happen to return NULL and we bail out from
> >> slab_alloc_node(). But this is a side-effect, not an intended protection.
> >> Also the CONFIG_TRACING variant of kmalloc_trace() would have called
> >> trace_kmalloc dereferencing s->size anyway even before this patch.
> >>
> >> I don't think we should add WARNS in the slab hot paths just to prevent this
> >> rare error of using slab too early. At most VM_WARN... would be acceptable
> >> but still not necessary as crashing immediately from a NULL pointer is
> >> sufficient.
> >>
> >> So IMHO mips should fix their soc init,
> >
> > Yes, for the mips fix, John has proposed to defer the calling of prom_soc_init(),
> > which looks reasonable.
> >
> >> and we should look into the
> >> CONFIG_TRACING=n variant of kmalloc_trace(), to pass orig_size properly.
> >
> > You mean check if the pointer is NULL and bail out early.
>
> No I mean here:
>
> #else /* CONFIG_TRACING */
> /* Save a function call when CONFIG_TRACING=n */
> static __always_inline __alloc_size(3)
> void *kmalloc_trace(struct kmem_cache *s, gfp_t flags, size_t size)
> {
> void *ret = kmem_cache_alloc(s, flags);
>
> ret = kasan_kmalloc(s, ret, size, flags);
> return ret;
> }
>
> we call kmem_cache_alloc() and discard the size parameter, so it will assume
> s->object_size (and as the side-effect, crash if s is NULL). We shouldn't
> add "s is NULL?" checks, but fix passing the size - probably switch to
> __kmem_cache_alloc_node()? and in the following kmalloc_node_trace() analogically.
Got it, thanks! I might have missed it during some rebasing for the
kmalloc wastage debug patch.
How about the following fix?
Thanks,
Feng
---
>From 9f9fa9da8946fd44625f873c0f51167357075be1 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang@xxxxxxxxx>
Date: Thu, 3 Nov 2022 21:32:10 +0800
Subject: [PATCH] mm/slub: Add missing orig_size parameter for wastage debug
commit 6edf2576a6cc ("mm/slub: enable debugging memory wasting of
kmalloc") was introduced for debugging kmalloc memory wastage,
and it missed to pass the original request size for kmalloc_trace()
and kmalloc_node_trace() in CONFIG_TRACING=n path.
Fix it by using __kmem_cache_alloc_node() with correct original
request size.
Fixes: 6edf2576a6cc ("mm/slub: enable debugging memory wasting of kmalloc")
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
---
include/linux/slab.h | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 90877fcde70b..9691afa569e1 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -469,6 +469,9 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node) __assume_kmalloc_alignm
__alloc_size(1);
void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t flags, int node) __assume_slab_alignment
__malloc;
+void *__kmem_cache_alloc_node(struct kmem_cache *s, gfp_t flags, int node,
+ size_t orig_size, unsigned long caller) __assume_slab_alignment
+ __malloc;
#ifdef CONFIG_TRACING
void *kmalloc_trace(struct kmem_cache *s, gfp_t flags, size_t size)
@@ -482,7 +485,8 @@ void *kmalloc_node_trace(struct kmem_cache *s, gfp_t gfpflags,
static __always_inline __alloc_size(3)
void *kmalloc_trace(struct kmem_cache *s, gfp_t flags, size_t size)
{
- void *ret = kmem_cache_alloc(s, flags);
+ void *ret = __kmem_cache_alloc_node(s, flags, NUMA_NO_NODE,
+ size, _RET_IP_);
ret = kasan_kmalloc(s, ret, size, flags);
return ret;
@@ -492,7 +496,8 @@ static __always_inline __alloc_size(4)
void *kmalloc_node_trace(struct kmem_cache *s, gfp_t gfpflags,
int node, size_t size)
{
- void *ret = kmem_cache_alloc_node(s, gfpflags, node);
+ void *ret = __kmem_cache_alloc_node(s, gfpflags, node,
+ size, _RET_IP_);
ret = kasan_kmalloc(s, ret, size, gfpflags);
return ret;
--
2.34.1
