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

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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: 76180d716f ("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>
This commit is contained in:
Michael Bommarito 2026-06-17 20:50:43 -04:00 committed by Greg Kroah-Hartman
parent 057df423bf
commit f63edb54d8
1 changed files with 2 additions and 2 deletions
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4
drivers/usb/gadget/configfs.c
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@ -1177,7 +1177,7 @@ static ssize_t os_desc_qw_sign_show(struct config_item *item, char *page)
struct gadget_info *gi = os_desc_item_to_gadget_info(item);
int res;
res = utf16s_to_utf8s((wchar_t *) gi->qw_sign, OS_STRING_QW_SIGN_LEN,
res = utf16s_to_utf8s((wchar_t *) gi->qw_sign, OS_STRING_QW_SIGN_LEN / 2,
UTF16_LITTLE_ENDIAN, page, PAGE_SIZE - 1);
page[res++] = '\n';
@ -1199,7 +1199,7 @@ static ssize_t os_desc_qw_sign_store(struct config_item *item, const char *page,
mutex_lock(&gi->lock);
res = utf8s_to_utf16s(page, l,
UTF16_LITTLE_ENDIAN, (wchar_t *) gi->qw_sign,
OS_STRING_QW_SIGN_LEN);
OS_STRING_QW_SIGN_LEN / 2);
if (res > 0)
res = len;
mutex_unlock(&gi->lock);