lib/test_hmm.c: handle src_pfns and dst_pfns allocation failure

The kcalloc() in dmirror_device_evict_chunk() will return null if the
physical memory has run out.  As a result, if src_pfns or dst_pfns is
dereferenced, the null pointer dereference bug will happen.

Moreover, the device is going away.  If the kcalloc() fails, the pages
mapping a chunk could not be evicted.  So add a __GFP_NOFAIL flag in
kcalloc().

Finally, as there is no need to have physically contiguous memory, Switch
kcalloc() to kvcalloc() in order to avoid failing allocations.

Link: https://lkml.kernel.org/r/20240312005905.9939-1-duoming@zju.edu.cn
Fixes: b2ef9f5a5cb3 ("mm/hmm/test: add selftest driver for HMM")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Cc: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 717dcb83012733e919000f13e6c035e86ba2abb4..b823ba7cb6a1568d5e975563e1648ddc45d7406d 100644 (file)
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -1226,8 +1226,8 @@ static void dmirror_device_evict_chunk(struct dmirror_chunk *chunk)
        unsigned long *src_pfns;
        unsigned long *dst_pfns;
 
-       src_pfns = kcalloc(npages, sizeof(*src_pfns), GFP_KERNEL);
-       dst_pfns = kcalloc(npages, sizeof(*dst_pfns), GFP_KERNEL);
+       src_pfns = kvcalloc(npages, sizeof(*src_pfns), GFP_KERNEL | __GFP_NOFAIL);
+       dst_pfns = kvcalloc(npages, sizeof(*dst_pfns), GFP_KERNEL | __GFP_NOFAIL);
 
        migrate_device_range(src_pfns, start_pfn, npages);
        for (i = 0; i < npages; i++) {
@@ -1250,8 +1250,8 @@ static void dmirror_device_evict_chunk(struct dmirror_chunk *chunk)
        }
        migrate_device_pages(src_pfns, dst_pfns, npages);
        migrate_device_finalize(src_pfns, dst_pfns, npages);
-       kfree(src_pfns);
-       kfree(dst_pfns);
+       kvfree(src_pfns);
+       kvfree(dst_pfns);
 }
 
 /* Removes free pages from the free list so they can't be re-allocated */