Patch "vmalloc: fix accounting with i915" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    vmalloc: fix accounting with i915

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     vmalloc-fix-accounting-with-i915.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5409233e1990be3d57f8faeb0fa5570cad12c2d8
Author: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Date:   Mon Dec 23 20:18:00 2024 +0000

    vmalloc: fix accounting with i915
    
    [ 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@xxxxxxxxxxxxx
    Fixes: b944afc9d64d ("mm: add a VM_MAP_PUT_PAGES flag for vmap")
    Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
    Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
    Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
    Reviewed-by: Balbir Singh <balbirs@xxxxxxxxxx>
    Acked-by: Michal Hocko <mhocko@xxxxxxxx>
    Cc: Christoph Hellwig <hch@xxxxxx>
    Cc: Muchun Song <muchun.song@xxxxxxxxx>
    Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
    Cc: "Uladzislau Rezki (Sony)" <urezki@xxxxxxxxx>
    Cc: <stable@xxxxxxxxxxxxxxx>
    Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index cd434f0ec47f..3cb1f59d1b53 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2621,7 +2621,8 @@ static void __vunmap(const void *addr, int deallocate_pages)
 			__free_pages(page, page_order);
 			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);
 	}