From: Jann Horn jannh@google.com
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@vger.kernel.org Fixes: ebe909e0fdb3 ("slub: improve bulk alloc strategy") Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/slub.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/mm/slub.c +++ b/mm/slub.c @@ -2932,6 +2932,15 @@ 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 */