[PATCH 6.1 39/60] vmalloc: fix accounting with i915

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthew Wilcox (Oracle) <willy@infradead.org>

[ Upstream commit a2e740e216f5bf49ccb83b6d490c72a340558a43 ]

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: b944afc9d64d ("mm: add a VM_MAP_PUT_PAGES flag for vmap")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Balbir Singh <balbirs@nvidia.com>
Acked-by: Michal 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/vmalloc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a0b650f50faa..7c6694514606 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2709,7 +2709,8 @@ static void __vunmap(const void *addr, int deallocate_pages)
 			struct page *page = area->pages[i];
 
 			BUG_ON(!page);
-			mod_memcg_page_state(page, MEMCG_VMALLOC, -1);
+			if (!(area->flags & VM_MAP_PUT_PAGES))
+				mod_memcg_page_state(page, MEMCG_VMALLOC, -1);
 			/*
 			 * High-order allocs for huge vmallocs are split, so
 			 * can be freed as an array of order-0 allocations
@@ -2717,7 +2718,8 @@ static void __vunmap(const void *addr, int deallocate_pages)
 			__free_pages(page, 0);
 			cond_resched();
 		}
-		atomic_long_sub(area->nr_pages, &nr_vmalloc_pages);
+		if (!(area->flags & VM_MAP_PUT_PAGES))
+			atomic_long_sub(area->nr_pages, &nr_vmalloc_pages);
 
 		kvfree(area->pages);
 	}
-- 
2.39.5