queue-4.19/mm-slab.c-kmemleak-no-scan-alien-caches.patch

   1 From ee8174f3693d65407585195ea5899e34760f4d5d Mon Sep 17 00:00:00 2001
   2 From: Qian Cai <cai@lca.pw>
   3 Date: Tue, 5 Mar 2019 15:42:03 -0800
   4 Subject: mm/slab.c: kmemleak no scan alien caches
   5
   6 [ Upstream commit 92d1d07daad65c300c7d0b68bbef8867e9895d54 ]
   7
   8 Kmemleak throws endless warnings during boot due to in
   9 __alloc_alien_cache(),
  10
  11     alc = kmalloc_node(memsize, gfp, node);
  12     init_arraycache(&alc->ac, entries, batch);
  13     kmemleak_no_scan(ac);
  14
  15 Kmemleak does not track the array cache (alc->ac) but the alien cache
  16 (alc) instead, so let it track the latter by lifting kmemleak_no_scan()
  17 out of init_arraycache().
  18
  19 There is another place that calls init_arraycache(), but
  20 alloc_kmem_cache_cpus() uses the percpu allocation where will never be
  21 considered as a leak.
  22
  23   kmemleak: Found object by alias at 0xffff8007b9aa7e38
  24   CPU: 190 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc2+ #2
  25   Call trace:
  26    dump_backtrace+0x0/0x168
  27    show_stack+0x24/0x30
  28    dump_stack+0x88/0xb0
  29    lookup_object+0x84/0xac
  30    find_and_get_object+0x84/0xe4
  31    kmemleak_no_scan+0x74/0xf4
  32    setup_kmem_cache_node+0x2b4/0x35c
  33    __do_tune_cpucache+0x250/0x2d4
  34    do_tune_cpucache+0x4c/0xe4
  35    enable_cpucache+0xc8/0x110
  36    setup_cpu_cache+0x40/0x1b8
  37    __kmem_cache_create+0x240/0x358
  38    create_cache+0xc0/0x198
  39    kmem_cache_create_usercopy+0x158/0x20c
  40    kmem_cache_create+0x50/0x64
  41    fsnotify_init+0x58/0x6c
  42    do_one_initcall+0x194/0x388
  43    kernel_init_freeable+0x668/0x688
  44    kernel_init+0x18/0x124
  45    ret_from_fork+0x10/0x18
  46   kmemleak: Object 0xffff8007b9aa7e00 (size 256):
  47   kmemleak:   comm "swapper/0", pid 1, jiffies 4294697137
  48   kmemleak:   min_count = 1
  49   kmemleak:   count = 0
  50   kmemleak:   flags = 0x1
  51   kmemleak:   checksum = 0
  52   kmemleak:   backtrace:
  53        kmemleak_alloc+0x84/0xb8
  54        kmem_cache_alloc_node_trace+0x31c/0x3a0
  55        __kmalloc_node+0x58/0x78
  56        setup_kmem_cache_node+0x26c/0x35c
  57        __do_tune_cpucache+0x250/0x2d4
  58        do_tune_cpucache+0x4c/0xe4
  59        enable_cpucache+0xc8/0x110
  60        setup_cpu_cache+0x40/0x1b8
  61        __kmem_cache_create+0x240/0x358
  62        create_cache+0xc0/0x198
  63        kmem_cache_create_usercopy+0x158/0x20c
  64        kmem_cache_create+0x50/0x64
  65        fsnotify_init+0x58/0x6c
  66        do_one_initcall+0x194/0x388
  67        kernel_init_freeable+0x668/0x688
  68        kernel_init+0x18/0x124
  69   kmemleak: Not scanning unknown object at 0xffff8007b9aa7e38
  70   CPU: 190 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc2+ #2
  71   Call trace:
  72    dump_backtrace+0x0/0x168
  73    show_stack+0x24/0x30
  74    dump_stack+0x88/0xb0
  75    kmemleak_no_scan+0x90/0xf4
  76    setup_kmem_cache_node+0x2b4/0x35c
  77    __do_tune_cpucache+0x250/0x2d4
  78    do_tune_cpucache+0x4c/0xe4
  79    enable_cpucache+0xc8/0x110
  80    setup_cpu_cache+0x40/0x1b8
  81    __kmem_cache_create+0x240/0x358
  82    create_cache+0xc0/0x198
  83    kmem_cache_create_usercopy+0x158/0x20c
  84    kmem_cache_create+0x50/0x64
  85    fsnotify_init+0x58/0x6c
  86    do_one_initcall+0x194/0x388
  87    kernel_init_freeable+0x668/0x688
  88    kernel_init+0x18/0x124
  89    ret_from_fork+0x10/0x18
  90
  91 Link: http://lkml.kernel.org/r/20190129184518.39808-1-cai@lca.pw
  92 Fixes: 1fe00d50a9e8 ("slab: factor out initialization of array cache")
  93 Signed-off-by: Qian Cai <cai@lca.pw>
  94 Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
  95 Cc: Christoph Lameter <cl@linux.com>
  96 Cc: Pekka Enberg <penberg@kernel.org>
  97 Cc: David Rientjes <rientjes@google.com>
  98 Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
  99 Cc: Catalin Marinas <catalin.marinas@arm.com>
 100 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 101 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 102 Signed-off-by: Sasha Levin <sashal@kernel.org>
 103 ---
 104  mm/slab.c | 17 +++++++++--------
 105  1 file changed, 9 insertions(+), 8 deletions(-)
 106
 107 diff --git a/mm/slab.c b/mm/slab.c
 108 index 364e42d5a399..b8e0ec74330f 100644
 109 --- a/mm/slab.c
 110 +++ b/mm/slab.c
 111 @@ -563,14 +563,6 @@ static void start_cpu_timer(int cpu)
 112
 113  static void init_arraycache(struct array_cache *ac, int limit, int batch)
 114  {
 115 -       /*
 116 -        * The array_cache structures contain pointers to free object.
 117 -        * However, when such objects are allocated or transferred to another
 118 -        * cache the pointers are not cleared and they could be counted as
 119 -        * valid references during a kmemleak scan. Therefore, kmemleak must
 120 -        * not scan such objects.
 121 -        */
 122 -       kmemleak_no_scan(ac);
 123         if (ac) {
 124                 ac->avail = 0;
 125                 ac->limit = limit;
 126 @@ -586,6 +578,14 @@ static struct array_cache *alloc_arraycache(int node, int entries,
 127         struct array_cache *ac = NULL;
 128
 129         ac = kmalloc_node(memsize, gfp, node);
 130 +       /*
 131 +        * The array_cache structures contain pointers to free object.
 132 +        * However, when such objects are allocated or transferred to another
 133 +        * cache the pointers are not cleared and they could be counted as
 134 +        * valid references during a kmemleak scan. Therefore, kmemleak must
 135 +        * not scan such objects.
 136 +        */
 137 +       kmemleak_no_scan(ac);
 138         init_arraycache(ac, entries, batchcount);
 139         return ac;
 140  }
 141 @@ -680,6 +680,7 @@ static struct alien_cache *__alloc_alien_cache(int node, int entries,
 142
 143         alc = kmalloc_node(memsize, gfp, node);
 144         if (alc) {
 145 +               kmemleak_no_scan(alc);
 146                 init_arraycache(&alc->ac, entries, batch);
 147                 spin_lock_init(&alc->lock);
 148         }
 149 --
 150 2.19.1
 151