Commit fd4d9c7d authored Mar 17, 2020 by Jann Horn Committed by Linus Torvalds Mar 18, 2020

mm: slub: add missing TID bump in kmem_cache_alloc_bulk()



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: ebe909e0 ("slub: improve bulk alloc strategy")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent ac309e77

mm/slub.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -3174,6 +3174,15 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
		void *object = c->freelist;

		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

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