Commit a2e740e2 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

vmalloc: fix accounting with i915 

If the caller of vmap() specifies VM_MAP_PUT_PAGES (currently only the
i915 driver), we will decrement nr_vmalloc_pages and MEMCG_VMALLOC in
vfree().  These counters are incremented by vmalloc() but not by vmap() so
this will cause an underflow.  Check the VM_MAP_PUT_PAGES flag before
decrementing either counter.

Link: https://lkml.kernel.org/r/20241211202538.168311-1-willy@infradead.org


Fixes: b944afc9 ("mm: add a VM_MAP_PUT_PAGES flag for vmap")
Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: default avatarBalbir Singh <balbirs@nvidia.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent faeec8e2

mm/vmalloc.c

+4 −2
Original line number Diff line number Diff line
@@ -3374,6 +3374,7 @@ void vfree(const void *addr) 
		struct page *page = vm->pages[i];



		BUG_ON(!page);

		if (!(vm->flags & VM_MAP_PUT_PAGES))

			mod_memcg_page_state(page, MEMCG_VMALLOC, -1);

		/*

		 * High-order allocs for huge vmallocs are split, so
@@ -3382,6 +3383,7 @@ void vfree(const void *addr) 
		__free_page(page);

		cond_resched();

	}

	if (!(vm->flags & VM_MAP_PUT_PAGES))

		atomic_long_sub(vm->nr_pages, &nr_vmalloc_pages);

	kvfree(vm->pages);

	kfree(vm);