On 12/12/24 07:25, Matthew Wilcox (Oracle) wrote:
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.
Fixes: b944afc9d64d (mm: add a VM_MAP_PUT_PAGES flag for vmap) Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Acked-by: Johannes Weiner hannes@cmpxchg.org
mm/vmalloc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index f009b21705c1..5c88d0e90c20 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3374,7 +3374,8 @@ 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
@@ -3382,7 +3383,8 @@ 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);}
I found another user kunit_iov_vector.c, but even it though it uses VM_MAP_PUT_PAGES, it does not call into vfree() (which I need to check for further bugs)
Reviewed-by: Balbir Singh balbirs@nvidia.com