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mm, slab: Check GFP_SLAB_BUG_MASK before alloc_pages in kmalloc_order

PATCH Superseded Long Li 4 participants 4 messages Jul 1, 2020

Subsystems (2)
Memory management Slab allocator

v3 of 6 Superseded Latest is v6 →

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Long Li

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#0 lore raw

PATCH v3 1/1 mm, slab: Check GFP_SLAB_BUG_MASK before alloc_pages in kmalloc_order

kmalloc cannot allocate memory from HIGHMEM. Allocating large amounts of memory currently bypasses the check and will simply leak the memory when page_address() returns NULL. To fix this, factor the GFP_SLAB_BUG_MASK check out of slab & slub, and call it from kmalloc_order() as well. In order to make the code clear, the warning message is put in one place.

Signed-off-by Long Li <[email protected]>

---

changes in V3:
-Put the warning message in one place
-updage the change log to be clear

 mm/slab.c        | 10 +++-------
 mm/slab.h        |  1 +
 mm/slab_common.c | 17 +++++++++++++++++
 mm/slub.c        |  9 ++-------
 4 files changed, 23 insertions(+), 14 deletions(-)
mm/slab.c +3 -7
index ac7a223d9ac3..2850fe3c5fb8 100644
@@ -2573,13 +2573,9 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep,
 	 * Be lazy and only check for valid flags here,  keeping it out of the
 	 * critical path in kmem_cache_alloc().
 	 */
-	if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
-		gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
-		flags &= ~GFP_SLAB_BUG_MASK;
-		pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
-				invalid_mask, &invalid_mask, flags, &flags);
-		dump_stack();
-	}
+	if (unlikely(flags & GFP_SLAB_BUG_MASK))
+		flags = kmalloc_invalid_flags(flags);
+
 	WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));
 	local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);
mm/slab.h +1 -0
index a06f3313e4a0..ab172dca8ce2 100644
@@ -90,6 +90,7 @@ void create_kmalloc_caches(slab_flags_t);
 struct kmem_cache *kmalloc_slab(size_t, gfp_t);
 #endif
 
+gfp_t kmalloc_invalid_flags(gfp_t flags);
 
 /* Functions provided by the slab allocators */
 int __kmem_cache_create(struct kmem_cache *, slab_flags_t flags);
mm/slab_common.c +17 -0
index a143a8c8f874..85a16e323906 100644
@@ -26,6 +26,8 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/kmem.h>
 
+#include "internal.h"
+
 #include "slab.h"
 
 enum slab_state slab_state;

@@ -805,6 +807,18 @@ void __init create_kmalloc_caches(slab_flags_t flags)
 }
 #endif /* !CONFIG_SLOB */
 
+gfp_t kmalloc_invalid_flags(gfp_t flags)
+{
+	gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
+
+	flags &= ~GFP_SLAB_BUG_MASK;
+	pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
+			invalid_mask, &invalid_mask, flags, &flags);
+	dump_stack();
+
+	return flags;
+}
+
 /*
  * To avoid unnecessary overhead, we pass through large allocation requests
  * directly to the page allocator. We use __GFP_COMP, because we will need to

@@ -815,6 +829,9 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
 	void *ret = NULL;
 	struct page *page;
 
+	if (unlikely(flags & GFP_SLAB_BUG_MASK))
+		flags = kmalloc_invalid_flags(flags);
+
 	flags |= __GFP_COMP;
 	page = alloc_pages(flags, order);
 	if (likely(page)) {
mm/slub.c +2 -7
index 62d2de56549e..039045211df9 100644
@@ -1817,13 +1817,8 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
 {
-	if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
-		gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
-		flags &= ~GFP_SLAB_BUG_MASK;
-		pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
-				invalid_mask, &invalid_mask, flags, &flags);
-		dump_stack();
-	}
+	if (unlikely(flags & GFP_SLAB_BUG_MASK))
+		flags = kmalloc_invalid_flags(flags);
 
 	return allocate_slab(s,
 		flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
Signature · 1 line
2.17.1
Reviewed-by on v3 1/1
#1 lore raw
Quoted 8 lines · Long Li

kmalloc cannot allocate memory from HIGHMEM. Allocating large amounts of memory currently bypasses the check and will simply leak the memory when page_address() returns NULL. To fix this, factor the GFP_SLAB_BUG_MASK check out of slab & slub, and call it from kmalloc_order() as well. In order to make the code clear, the warning message is put in one place.

Signed-off-by Long Li <[email protected]>
Reviewed-by Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by on v3 1/1
#2 lore raw
In reply to Long Li
Quoted 9 lines · Long Li

kmalloc cannot allocate memory from HIGHMEM. Allocating large amounts of memory currently bypasses the check and will simply leak the memory when page_address() returns NULL. To fix this, factor the GFP_SLAB_BUG_MASK check out of slab & slub, and call it from kmalloc_order() as well. In order to make the code clear, the warning message is put in one place.

Signed-off-by Long Li <[email protected]>
Reviewed-by Pekka Enberg <[email protected]>
reviewer
#3 lore raw
In reply to Long Li
Quoted 11 lines · Long Li
mm/slab.c +0 -3
index ac7a223d9ac3..2850fe3c5fb8 100644
@@ -2573,13 +2573,9 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep,
 	 * Be lazy and only check for valid flags here,  keeping it out of the
 	 * critical path in kmem_cache_alloc().
 	 */
-	if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
-		gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
-		flags &= ~GFP_SLAB_BUG_MASK;

mm/slab.c static struct page *cache_grow_begin(struct kmem_cache *cachep, · line 2581

Quoted 10 lines
mm/slab.c +3 -4
-		pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
-				invalid_mask, &invalid_mask, flags, &flags);
-		dump_stack();
-	}
+	if (unlikely(flags & GFP_SLAB_BUG_MASK))
+		flags = kmalloc_invalid_flags(flags);
+
 	WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));
 	local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);

Is this name correct? kmalloc_invalid_flags() masks off the invalid flags and returns the valid flags :) Maybe kmalloc_check_flags()?