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authorDongli Zhang <dongli.zhang@oracle.com>2020-06-01 21:45:47 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 10:59:06 -0700
commit52f23478081ae0dcdb95d1650ea1e7d52d586829 (patch)
treeb083e524b08b948bff4e01bf440d5c8f998990bb /mm/slub.c
parent49f2d2419d60a103752e5fbaf158cf8d07c0d884 (diff)
mm/slub.c: fix corrupted freechain in deactivate_slab()
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. [akpm@linux-foundation.org: fix build with CONFIG_SLAB_DEBUG=n] Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Joe Jin <joe.jin@oracle.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Link: http://lkml.kernel.org/r/20200331031450.12182-1-dongli.zhang@oracle.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c27
1 files changed, 27 insertions, 0 deletions
diff --git a/mm/slub.c b/mm/slub.c
index b762450fc9f0..6972c27ae394 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -679,6 +679,20 @@ 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 */
@@ -1410,6 +1424,11 @@ 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 */
/*
@@ -2093,6 +2112,14 @@ 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;