[PATCH] lib/test_hmm: fix memory leak in dmirror_migrate_to_system()

[Hao Ge <hao.ge@linux.dev>]

Move the kvcalloc() calls after the early return checks to avoid
leaking src_pfns and dst_pfns when end < start or mmget_not_zero()
fails.

Fixes: 775465fd26a3 ("lib/test_hmm: add zone device private THP test infrastructure")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Hao Ge <hao.ge@linux.dev>
---
Sashiko report: https://sashiko.dev/#/patchset/20260513082525.154036-1-hao.ge@linux.dev

It looks like the other issue reported by Sashiko (dmirror_devmem_fault()
leaking args.src/args.dst on migrate_vma_setup() failure) may have already
been addressed in mm-new by 84808b0e9f75 ("lib/test_hmm: fix error path in
dmirror_devmem_fault()").
---
 lib/test_hmm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 213504915737..0c02871b97ba 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -1111,9 +1111,6 @@ static int dmirror_migrate_to_system(struct dmirror *dmirror,
 	unsigned long *src_pfns;
 	unsigned long *dst_pfns;
 
-	src_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*src_pfns), GFP_KERNEL | __GFP_NOFAIL);
-	dst_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*dst_pfns), GFP_KERNEL | __GFP_NOFAIL);
-
 	start = cmd->addr;
 	end = start + size;
 	if (end < start)
@@ -1123,6 +1120,9 @@ static int dmirror_migrate_to_system(struct dmirror *dmirror,
 	if (!mmget_not_zero(mm))
 		return -EINVAL;
 
+	src_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*src_pfns), GFP_KERNEL | __GFP_NOFAIL);
+	dst_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*dst_pfns), GFP_KERNEL | __GFP_NOFAIL);
+
 	cmd->cpages = 0;
 	mmap_read_lock(mm);
 	for (addr = start; addr < end; addr = next) {
-- 
2.25.1