[PATCH] ntfs3: check if more than chunk-size bytes are written

[Andrew Ballance]

#syz test

a incorrectly formatted chunk may decompress into
more than LZNT_CHUNK_SIZE bytes and a index out of bounds
will occur in s_max_off.

Signed-off-by: Andrew Ballance <andrewjballance@xxxxxxxxx>
---
 fs/ntfs3/lznt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ntfs3/lznt.c b/fs/ntfs3/lznt.c
index 4aae598d6d88..fdc9b2ebf341 100644
--- a/fs/ntfs3/lznt.c
+++ b/fs/ntfs3/lznt.c
@@ -236,6 +236,9 @@ static inline ssize_t decompress_chunk(u8 *unc, u8 *unc_end, const u8 *cmpr,
 
 	/* Do decompression until pointers are inside range. */
 	while (up < unc_end && cmpr < cmpr_end) {
+		// return err if more than LZNT_CHUNK_SIZE bytes are written
+		if (up - unc > LZNT_CHUNK_SIZE)
+			return -EINVAL;
 		/* Correct index */
 		while (unc + s_max_off[index] < up)
 			index += 1;
-- 
2.45.0