From: Shivam Kalra Date: Tue, 19 May 2026 12:12:16 +0000 (+0530) Subject: mm/vmalloc: use physical page count in vread_iter() for VM_ALLOC areas X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=0bca23804632cc7275fc5f67191b6be58993cd28;p=thirdparty%2Flinux.git mm/vmalloc: use physical page count in vread_iter() for VM_ALLOC areas For VM_ALLOC areas in vread_iter(), derive the vm area size from vm->nr_pages rather than get_vm_area_size(). Only VM_ALLOC areas are subject to vrealloc() shrinking, which frees pages without reducing the virtual reservation size. Switch to using vm->nr_pages for VM_ALLOC areas so the reader remains correct once shrink support is added. Other mapping types (vmap, ioremap) do not initialize nr_pages and will continue using get_vm_area_size(). [shivamkalra98@zohomail.in: add an nr_pages check] Link: https://lore.kernel.org/aff47da5-4fd5-481d-be18-e1eb99639490@zohomail.in Link: https://lore.kernel.org/20260519-vmalloc-shrink-v14-3-70b96ee3e9c9@zohomail.in Signed-off-by: Shivam Kalra Reviewed-by: Uladzislau Rezki (Sony) Cc: Alice Ryhl Cc: Danilo Krummrich Signed-off-by: Andrew Morton --- diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 3e159b74cfab..bc21bf8e188b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4666,7 +4666,18 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count) smp_rmb(); vaddr = (char *) va->va_start; - size = vm ? get_vm_area_size(vm) : va_size(va); + if (vm) + /* + * For VM_ALLOC areas, use nr_pages rather than + * get_vm_area_size() because vrealloc() may shrink + * the mapping without updating area->size. Other + * mapping types (vmap, ioremap) don't set nr_pages. + */ + size = (vm->flags & VM_ALLOC && vm->nr_pages) ? + (vm->nr_pages << PAGE_SHIFT) : + get_vm_area_size(vm); + else + size = va_size(va); if (addr >= vaddr + size) goto next_va;