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-rw-r--r--mm/madvise.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/mm/madvise.c b/mm/madvise.c
index 2baa93ca2310..c7105ec6d08c 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -813,7 +813,14 @@ static bool madvise_dontneed_free_valid_vma(struct vm_area_struct *vma,
if (start & ~huge_page_mask(hstate_vma(vma)))
return false;
- *end = ALIGN(*end, huge_page_size(hstate_vma(vma)));
+ /*
+ * Madvise callers expect the length to be rounded up to PAGE_SIZE
+ * boundaries, and may be unaware that this VMA uses huge pages.
+ * Avoid unexpected data loss by rounding down the number of
+ * huge pages freed.
+ */
+ *end = ALIGN_DOWN(*end, huge_page_size(hstate_vma(vma)));
+
return true;
}
@@ -828,6 +835,9 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
if (!madvise_dontneed_free_valid_vma(vma, start, &end, behavior))
return -EINVAL;
+ if (start == end)
+ return 0;
+
if (!userfaultfd_remove(vma, start, end)) {
*prev = NULL; /* mmap_lock has been dropped, prev is stale */