6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kees Cook kees@kernel.org
commit 70d1eb031a68cbde4eed8099674be21778441c94 upstream.
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: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing") Signed-off-by: Kees Cook kees@kernel.org Tested-by: Pawan 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: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/vmalloc.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
--- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4097,8 +4097,8 @@ void *vrealloc_noprof(const void *p, siz * 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); @@ -4111,9 +4111,11 @@ void *vrealloc_noprof(const void *p, siz 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; }