[PATCH] v4l2-tpg: array index could become negative

[Hans Verkuil]

text[s] is a signed char, so using that as index into the font8x16 array
can result in negative indices. Cast it to u8 to be safe.

Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
Reported-by: syzbot+ccf0a61ed12f2a731...@syzkaller.appspotmail.com
---
diff --git a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c 
b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
index fa483b95bc5a..d9a590ae7545 100644
--- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
+++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
@@ -1769,7 +1769,7 @@ typedef struct { u16 __; u8 _; } __packed x24;
                unsigned s;     \
        \
                for (s = 0; s < len; s++) {     \
-                       u8 chr = font8x16[text[s] * 16 + line]; \
+                       u8 chr = font8x16[(u8)text[s] * 16 + line];     \
        \
                        if (hdiv == 2 && tpg->hflip) { \
                                pos[3] = (chr & (0x01 << 6) ? fg : bg); \