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.
Fixes: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing")
Tested-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Signed-off-by: Kees Cook <kees@xxxxxxxxxx>
---
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Uladzislau Rezki <urezki@xxxxxxxxx>
Cc: <linux-mm@xxxxxxxxx>
---
mm/vmalloc.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 74bd00fd734d..00cf1b575c89 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -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;
}
--
2.34.1
