[PATCH mm/stable] mm: fix vrealloc()'s KASAN poisoning logic

[Andrii Nakryiko]

When vrealloc() reuses already allocated vmap_area, we need to
re-annotate poisoned and unpoisoned portions of underlying memory
according to the new size.

Note, hard-coding KASAN_VMALLOC_PROT_NORMAL might not be exactly
correct, but KASAN flag logic is pretty involved and spread out
throughout __vmalloc_node_range_noprof(), so I'm using the bare minimum
flag here and leaving the rest to mm people to refactor this logic and
reuse it here.

Fixes: 3ddc2fefe6f3 ("mm: vmalloc: implement vrealloc()")
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
 mm/vmalloc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 7ed39d104201..f009b21705c1 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4093,7 +4093,8 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
 		/* Zero out spare memory. */
 		if (want_init_on_alloc(flags))
 			memset((void *)p + size, 0, old_size - size);
-
+		kasan_poison_vmalloc(p + size, old_size - size);
+		kasan_unpoison_vmalloc(p, size, KASAN_VMALLOC_PROT_NORMAL);
 		return (void *)p;
 	}
 
-- 
2.43.5