[PATCH v6 2/6] mm/vmalloc: fix vrealloc() grow-in-place check

[Shivam Kalra via B4 Relay <devnull+shivamkalra98.zohomail.in@kernel.org>]

From: Shivam Kalra <shivamkalra98@zohomail.in>

Fix 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()).

The virtual reservation size (get_vm_area_size()) does not decrease when
pages are freed during a shrink operation. Consequently, without this fix,
a subsequent grow-in-place operation after a shrink would incorrectly
succeed and attempt to access freed pages. Correcting this check is a
prerequisite for the upcoming vrealloc() shrink functionality.

Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
 mm/vmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 3977398e56e4..7bc7a6892c1a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4361,7 +4361,7 @@ 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