mm/slub.c: fix corrupted freechain in deactivate_slab()

OpenAnolis Bug Tracker: 0000546

task #29494601

commit 52f2347 upstream

The slub_debug is able to fix the corrupted slab freelist/page.
However, alloc_debug_processing() only checks the validity of current
and next freepointer during allocation path.  As a result, once some
objects have their freepointers corrupted, deactivate_slab() may lead to
page fault.

Below is from a test kernel module when 'slub_debug=PUF,kmalloc-128
slub_nomerge'.  The test kernel corrupts the freepointer of one free
object on purpose.  Unfortunately, deactivate_slab() does not detect it
when iterating the freechain.

  BUG: unable to handle page fault for address: 00000000123456f8
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP PTI
  ... ...
  RIP: 0010:deactivate_slab.isra.92+0xed/0x490
  ... ...
  Call Trace:
   ___slab_alloc+0x536/0x570
   __slab_alloc+0x17/0x30
   __kmalloc+0x1d9/0x200
   ext4_htree_store_dirent+0x30/0xf0
   htree_dirblock_to_tree+0xcb/0x1c0
   ext4_htree_fill_tree+0x1bc/0x2d0
   ext4_readdir+0x54f/0x920
   iterate_dir+0x88/0x190
   __x64_sys_getdents+0xa6/0x140
   do_syscall_64+0x49/0x170
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

Therefore, this patch adds extra consistency check in deactivate_slab().
Once an object's freepointer is corrupted, all following objects
starting at this object are isolated.

[[email protected]: fix build with CONFIG_SLAB_DEBUG=n]
Signed-off-by: Dongli Zhang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Joe Jin <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: zhongjiang-ali <[email protected]>
Acked-by: Xunlei Pang <[email protected]>
Acked-by: Joseph Qi <[email protected]>

mm/slub.c

@@ -645,6 +645,20 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...)
 	va_end(args);
 }
 
+static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
+			       void *freelist, void *nextfree)
+{
+	if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
+	    !check_valid_pointer(s, page, nextfree)) {
+		object_err(s, page, freelist, "Freechain corrupt");
+		freelist = NULL;
+		slab_fix(s, "Isolate corrupted freechain");
+		return true;
+	}
+
+	return false;
+}
+
 static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
 {
 	unsigned int off;	/* Offset of last byte */
@@ -1328,6 +1342,11 @@ static inline void inc_slabs_node(struct kmem_cache *s, int node,
 static inline void dec_slabs_node(struct kmem_cache *s, int node,
 							int objects) {}
 
+static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
+			       void *freelist, void *nextfree)
+{
+	return false;
+}
 #endif /* CONFIG_SLUB_DEBUG */
 
 /*
@@ -2015,6 +2034,14 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 		void *prior;
 		unsigned long counters;
 
+		/*
+		 * If 'nextfree' is invalid, it is possible that the object at
+		 * 'freelist' is already corrupted.  So isolate all objects
+		 * starting at 'freelist'.
+		 */
+		if (freelist_corrupted(s, page, freelist, nextfree))
+			break;
+
 		do {
 			prior = page->freelist;
 			counters = page->counters;