6.12-stable review patch. If anyone has any objections, please let me know.
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From: Matthew Wilcox (Oracle) willy@infradead.org
commit a2e740e216f5bf49ccb83b6d490c72a340558a43 upstream.
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: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/vmalloc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3369,7 +3369,8 @@ void vfree(const void *addr) struct page *page = vm->pages[i];
BUG_ON(!page); - mod_memcg_page_state(page, MEMCG_VMALLOC, -1); + if (!(vm->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 @@ -3377,7 +3378,8 @@ void vfree(const void *addr) __free_page(page); cond_resched(); } - atomic_long_sub(vm->nr_pages, &nr_vmalloc_pages); + if (!(vm->flags & VM_MAP_PUT_PAGES)) + atomic_long_sub(vm->nr_pages, &nr_vmalloc_pages); kvfree(vm->pages); kfree(vm); }