[PATCH 2/2] ntfs3: fix integer overflow in run_unpack() volume boundary check

[tobgaertner]

From: Tobias Gaertner <tob.gaertner@xxxxxx>

The volume boundary check `lcn + len > sbi->used.bitmap.nbits` uses raw
addition which can wrap around for large lcn and len values, bypassing
the validation.  Use check_add_overflow() as is already done for the
adjacent prev_lcn + dlcn and vcn64 + len checks added by commit
3ac37e100385 ("ntfs3: Fix integer overflow in run_unpack()").

Found by fuzzing with a source-patched harness (LibAFL + QEMU).

Fixes: 82cae269cfa95 ("fs/ntfs3: Add initialization of super block")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tobias Gaertner <tob.gaertner@xxxxxx>
---
 fs/ntfs3/run.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/ntfs3/run.c b/fs/ntfs3/run.c
index c3c6917fa..a68000bd4 100644
--- a/fs/ntfs3/run.c
+++ b/fs/ntfs3/run.c
@@ -1027,9 +1027,15 @@ int run_unpack(struct runs_tree *run, struct ntfs_sb_info *sbi, CLST ino,
 			return -EOPNOTSUPP;
 		}
 #endif
-		if (lcn != SPARSE_LCN64 && lcn + len > sbi->used.bitmap.nbits) {
-			/* LCN range is out of volume. */
-			return -EINVAL;
+		if (lcn != SPARSE_LCN64) {
+			u64 lcn_end;
+
+			if (check_add_overflow(lcn, len, &lcn_end))
+				return -EINVAL;
+			if (lcn_end > sbi->used.bitmap.nbits) {
+				/* LCN range is out of volume. */
+				return -EINVAL;
+			}
 		}
 
 		if (!run)
-- 
2.43.0