From: Jann Horn <jannh@xxxxxxxxxx>
commit fd4d9c7d0c71866ec0c2825189ebd2ce35bd95b8 upstream.
When kmem_cache_alloc_bulk() attempts to allocate N objects from a percpu
freelist of length M, and N > M > 0, it will first remove the M elements
from the percpu freelist, then call ___slab_alloc() to allocate the next
element and repopulate the percpu freelist. ___slab_alloc() can re-enable
IRQs via allocate_slab(), so the TID must be bumped before ___slab_alloc()
to properly commit the freelist head change.
Fix it by unconditionally bumping c->tid when entering the slowpath.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: ebe909e0fdb3 ("slub: improve bulk alloc strategy")
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3104,6 +3104,15 @@ int kmem_cache_alloc_bulk(struct kmem_ca
if (unlikely(!object)) {
/*
+ * We may have removed an object from c->freelist using
+ * the fastpath in the previous iteration; in that case,
+ * c->tid has not been bumped yet.
+ * Since ___slab_alloc() may reenable interrupts while
+ * allocating memory, we should bump c->tid now.
+ */
+ c->tid = next_tid(c->tid);
+
+ /*
* Invoking slow path likely have side-effect
* of re-populating per CPU c->freelist
*/
