media: v4l2-tpg: array index could become negative

commit e5f71a27fa12c1a1b02ad478a568e76260f1815e upstream.

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 <hverkuil-cisco@xs4all.nl>
Reported-by: syzbot+ccf0a61ed12f2a7313ee@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>      # for v4.7 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
index f40ab57..2036b94 100644 (file)
--- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
+++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
@@ -1738,7 +1738,7 @@ 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); \