From: Sean Rees <sean@xxxxxxxxxx>
Subject: mm/slub.c: fix random_seq offset destruction
210e7a43fa90 ("mm: SLUB freelist randomization") broke USB hub
initialisation as described in
https://bugzilla.kernel.org/show_bug.cgi?id=177551.
Bail out early from init_cache_random_seq if s->random_seq is already
initialised. This prevents destroying the previously computed random_seq
offsets later in the function.
If the offsets are destroyed, then shuffle_freelist will truncate
page->freelist to just the first object (orphaning the rest).
Fixes: 210e7a43fa90 ("mm: SLUB freelist randomization")
Link: http://lkml.kernel.org/r/20170207140707.20824-1-sean@xxxxxxxxxx
Signed-off-by: Sean Rees <sean@xxxxxxxxxx>
Reported-by: <userwithuid@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Thomas Garnier <thgarnie@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 4 ++++
1 file changed, 4 insertions(+)
diff -puN mm/slub.c~mm-slub-fix-random_seq-offset-destruction mm/slub.c
--- a/mm/slub.c~mm-slub-fix-random_seq-offset-destruction
+++ a/mm/slub.c
@@ -1422,6 +1422,10 @@ static int init_cache_random_seq(struct
int err;
unsigned long i, count = oo_objects(s->oo);
+ /* Bailout if already initialised */
+ if (s->random_seq)
+ return 0;
+
err = cache_random_seq_create(s, count, GFP_KERNEL);
if (err) {
pr_err("SLUB: Unable to initialize free list for %s\n",
_
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