Commit 70d1eb03 authored by Kees Cook's avatar Kees Cook Committed by Andrew Morton
Browse files

mm: vmalloc: only zero-init on vrealloc shrink 

The common case is to grow reallocations, and since init_on_alloc will
have already zeroed the whole allocation, we only need to zero when
shrinking the allocation.

Link: https://lkml.kernel.org/r/20250515214217.619685-2-kees@kernel.org


Fixes: a0309faf ("mm: vmalloc: support more granular vrealloc() sizing")
Signed-off-by: default avatarKees Cook <kees@kernel.org>
Tested-by: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: "Erhard F." <erhard_f@mailbox.org>
Cc: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f7a35a3c

mm/vmalloc.c

+7 −5
Original line number Diff line number Diff line
@@ -4093,8 +4093,8 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) 
	 * would be a good heuristic for when to shrink the vm_area?

	 */

	if (size <= old_size) {

		/* Zero out "freed" memory. */

		if (want_init_on_free())

		/* Zero out "freed" memory, potentially for future realloc. */

		if (want_init_on_free() || want_init_on_alloc(flags))

			memset((void *)p + size, 0, old_size - size);

		vm->requested_size = size;

		kasan_poison_vmalloc(p + size, old_size - size);
@@ -4107,9 +4107,11 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) 
	if (size <= alloced_size) {

		kasan_unpoison_vmalloc(p + old_size, size - old_size,

				       KASAN_VMALLOC_PROT_NORMAL);

		/* Zero out "alloced" memory. */

		if (want_init_on_alloc(flags))

			memset((void *)p + old_size, 0, size - old_size);

		/*

		 * No need to zero memory here, as unused memory will have

		 * already been zeroed at initial allocation time or during

		 * realloc shrink time.

		 */

		vm->requested_size = size;

		return (void *)p;

	}