[PATCH v10 2/4] mm/vmalloc: use physical page count for vrealloc() grow-in-place check

Shivam Kalra via B4 Relay
2026-04-04T08:37:16Z

From: Shivam Kalra <shivamkalra98@zohomail.in>

Update the grow-in-place check in vrealloc() to compare the requested size
against the actual physical page count (vm->nr_pages) rather than the
virtual area size (alloced_size, derived from get_vm_area_size()).

Currently both values are equivalent, but the upcoming vrealloc() shrink
functionality will free pages without reducing the virtual reservation
size. After such a shrink, the old alloced_size-based comparison would
incorrectly allow a grow-in-place operation to succeed and attempt to
access freed pages. Switch to vm->nr_pages now so the check remains
correct once shrink support is added.

Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
mm/vmalloc.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8dd7df79c5c5..d0ebe16b584a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4343,6 +4343,12 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align
if (unlikely(flags & __GFP_THISNODE) && nid != NUMA_NO_NODE &&
nid != page_to_nid(vmalloc_to_page(p)))
goto need_realloc;
+ } else {
+ /*
+ * If p is NULL, vrealloc behaves exactly like vmalloc.
+ * Skip the shrink and in-place grow paths.
+ */
+ goto need_realloc;
}

/*
@@ -4361,7 +4367,7 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align
/*
* We already have the bytes available in the allocation; use them.
*/
- if (size <= alloced_size) {
+ if (size <= (size_t)vm->nr_pages << PAGE_SHIFT) {
/*
* No need to zero memory here, as unused memory will have
* already been zeroed at initial allocation time or during

--
2.43.0