mm/pagewalk.c: report holes in hugetlb ranges
This matters at least for the mincore syscall, which will otherwise copy
uninitialized memory from the page allocator to userspace. It is
probably also a correctness error for /proc/$pid/pagemap, but I haven't
tested that.
Removing the `walk->hugetlb_entry` condition in walk_hugetlb_range() has
no effect because the caller already checks for that.
This only reports holes in hugetlb ranges to callers who have specified
a hugetlb_entry callback.
This issue was found using an AFL-based fuzzer.
v2:
- don't crash on ->pte_hole==NULL (Andrew Morton)
- add Cc stable (Andrew Morton)
Fixes: 1e25a271c8ac ("mincore: apply page table walker on do_mincore()")
Signed-off-by: Jann Horn <jannh@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 8bd4afa..23a3e41 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -188,8 +188,12 @@
do {
next = hugetlb_entry_end(h, addr, end);
pte = huge_pte_offset(walk->mm, addr & hmask, sz);
- if (pte && walk->hugetlb_entry)
+
+ if (pte)
err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
+ else if (walk->pte_hole)
+ err = walk->pte_hole(addr, next, walk);
+
if (err)
break;
} while (addr = next, addr != end);
