Input: iforce - invert valid length check when fetching device IDs

syzbot is reporting uninitialized value at iforce_init_device() [1], for
commit 6ac0aec6b0a6 ("Input: iforce - allow callers supply data buffer
when fetching device IDs") is checking that valid length is shorter than
bytes to read. Since iforce_get_id_packet() stores valid length when
returning 0, the caller needs to check that valid length is longer than or
equals to bytes to read.

Reported-by: syzbot <syzbot+4dd880c1184280378821@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 6ac0aec6b0a6 ("Input: iforce - allow callers supply data buffer when fetching device IDs")
Link: https://lore.kernel.org/r/531fb432-7396-ad37-ecba-3e42e7f56d5c@I-love.SAKURA.ne.jp
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/joystick/iforce/iforce-main.c b/drivers/input/joystick/iforce/iforce-main.c
index b86de1312512bd3a1b41ab795956bdbe317f5974..84b87526b7ba319d98494c53a06364e5369f4d23 100644 (file)
--- a/drivers/input/joystick/iforce/iforce-main.c
+++ b/drivers/input/joystick/iforce/iforce-main.c
@@ -273,22 +273,22 @@ int iforce_init_device(struct device *parent, u16 bustype,
  * Get device info.
  */
 
-       if (!iforce_get_id_packet(iforce, 'M', buf, &len) || len < 3)
+       if (!iforce_get_id_packet(iforce, 'M', buf, &len) && len >= 3)
                input_dev->id.vendor = get_unaligned_le16(buf + 1);
        else
                dev_warn(&iforce->dev->dev, "Device does not respond to id packet M\n");
 
-       if (!iforce_get_id_packet(iforce, 'P', buf, &len) || len < 3)
+       if (!iforce_get_id_packet(iforce, 'P', buf, &len) && len >= 3)
                input_dev->id.product = get_unaligned_le16(buf + 1);
        else
                dev_warn(&iforce->dev->dev, "Device does not respond to id packet P\n");
 
-       if (!iforce_get_id_packet(iforce, 'B', buf, &len) || len < 3)
+       if (!iforce_get_id_packet(iforce, 'B', buf, &len) && len >= 3)
                iforce->device_memory.end = get_unaligned_le16(buf + 1);
        else
                dev_warn(&iforce->dev->dev, "Device does not respond to id packet B\n");
 
-       if (!iforce_get_id_packet(iforce, 'N', buf, &len) || len < 2)
+       if (!iforce_get_id_packet(iforce, 'N', buf, &len) && len >= 2)
                ff_effects = buf[1];
        else
                dev_warn(&iforce->dev->dev, "Device does not respond to id packet N\n");