usb: gadget: configfs: fix out-of-bounds read of qw_sign

os_desc_qw_sign_show() passes OS_STRING_QW_SIGN_LEN as the input
length to utf16s_to_utf8s(), but that argument counts UTF-16 code
units while OS_STRING_QW_SIGN_LEN (14) is the byte size of qw_sign[].
The array holds only OS_STRING_QW_SIGN_LEN / 2 (7) code units, so the
conversion reads up to 7 units (14 bytes) past the end of qw_sign[]
into the following members of struct gadget_info when the stored
signature fills the array without a NUL terminator, exposing those
bytes through the configfs attribute.

The store path halves the count for its input bound but passes the
full byte count as the utf8s_to_utf16s() output limit; use the
destination code-unit count in both directions.

Fixes: 76180d716f91 ("usb: gadget: configfs: make qw_sign attribute symmetric")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Link: https://patch.msgid.link/20260618005043.1581707-1-michael.bommarito@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions