From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f178.google.com (mail-pf1-f178.google.com [209.85.210.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2DBF637F333 for ; Sun, 16 Aug 2026 00:54:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786841688; cv=none; b=UPKYxWqLJgOsM/uAXl55j+YdCPzHgNPQaqFWL1f5rOpsCEaGIR1nH119kBtMFQOvCmMyCWHpRMvgy7WhjEtGh0CLDzK+Tx/VwCzGEr3oLCrxzQCwRM6AIT+KvVRzVB48AzjT/ctmz/1+WZHWaC6b/urg96UeB9YJUZ73wK8B7c8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786841688; c=relaxed/simple; bh=dhYWpeBhPVGAijpVY9A0yj0k2r/Nn2Iq0rU9yCWTMVk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=LBrsv3E0zImSpbuaKbhCdnCbGZOs6ii11HwLd6w8/DjldJ1j24XKHuVFO1lvh92XBJYrR84xPGagjCevlsepPn2tbDnf7H9VilmGHD36octEHgBLVxKLm4PK2FM90i0DcMUYBWX9EPUg5izIkAT2x4/kBnJVrR8pyv8FZZrE5+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=BqTgSM2k; arc=none smtp.client-ip=209.85.210.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="BqTgSM2k" Received: by mail-pf1-f178.google.com with SMTP id d2e1a72fcca58-84847482584so1547029b3a.0 for ; Sat, 15 Aug 2026 17:54:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1786841685; x=1787446485; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=LhBayU0zL3CCNfcwVZJNkjqGRYpc/saRBdtRAgZU1O0=; b=BqTgSM2kB/RstI3aWfegYTagtXy4EEpv28qbfM5UT3Jv/wthdSAq0S9KBPISIeHoaI YWw+VxYnqkqGzWLYN99bTEgTu4pi9xvjN5smTAf5+ausLBX6LW0ocascFBLCktBY0Ng2 +tSuFomfa3uRcvnkfNJP3HpwchtiaQYkizxbTGifcW7/ShGj3cO+0QDsAYoMsaDmvEkQ Pu5lzW8mLc4NKAb7Qpur9wzXGLswk0iEHMnZHdKsKUoUHgDTQVdoog7lWaf4+TecQJpe l+BQiaS/p9m/FvMk8lHzyJHlUCgLOHF24DIguWh2ldzFde2MJLvHhiL2nskgw260ofvj mtcw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786841685; x=1787446485; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=LhBayU0zL3CCNfcwVZJNkjqGRYpc/saRBdtRAgZU1O0=; b=phhIseGyxKTBBPgwsqYJ6wYyN97zYLCBDY3J+1djcqc6q0CjBkuVAZdEOVyqdyGF7d saybHRJAaIscNlrwwQ/4z2bty7lwBxFdvRTo1+IkDXUfliJva2XI/SrmL0RXfny1CPK5 pYhaF27KQ2NQEKgsXb723rpXkqsFruffOGhK3AK/YhkgqJZ9tHWYsza+knTQBm+Jwz4c nt4NlsxoHriMATN4p2clS6mF4BP1v4MgkQXS7U6KAwy1QAjY6GHat6zFqcm1//RHdY5Z xves4i+RVvSLIDa+hanQJGl1bkzGkopkDkGz0soDU1XvVR5lErTEj6MefNCc+ox1YBOQ vD8Q== X-Forwarded-Encrypted: i=1; AHgh+RrFqC5yImjX+jJu90E6n9XMKXJGM3ZJ0B/z74LSrwTnCwdl1OQQO6PFmHi+8vDSmh68/UCepLrjBlnoSF0=@vger.kernel.org X-Gm-Message-State: AOJu0Yx0xRBALrFZEgmc0ftB1YYNEjLFUqxytBQwtT/4N0eEEuOwpy0l dqlUzU+lAH32QcNMSdo1h1YUxiy/yV95CnSCZTADtmNWh+TL1g9gALKx X-Gm-Gg: AR+sD11nWRcQGo1hVXE+t29X7YtC13GuU1qLKZZHnkyCBBobDgD8pRTrOLRlcq2DtOR 8UkT7nwKUwSg1bN8qVliXCX+1Jc0bOYziz5lyVrRdNSFkLWNG3zqwWVS+OlFqrk8i13ZGYp9yC4 NUicHDxA1mvrS4IRVR9/vGLUEAR6iVi4FvF0P63RI2J8tzmIPtD1aZ+UkphJySC/hN+pXtP4DXC Drx9T13AlUfds+6lWE8Lt6sXSZoBh+AZlpGzSGE/mXBHY7GrMrNXyeI+0NMiL67s+SdVH43JLwJ eptQhWaTXw5TSSoNFgw0a8NHDfumx79RSSsSMmldzDdQ5+dtCqo/0kDyvMSTV8L3SfsRHuePvWW 1PSS/2LCPtja3ihgjfuWnaqKwMegz9Dzo0+1COZg75XtTOJgT2o0+tFPQGndv20BOGTwA+RV9Ki BtRG5jRwW81uVXT3IzeOyAh++MfUdYrxrlsboazEjIoIYyv2qOYIp18Q== X-Received: by 2002:a05:6a00:a889:b0:846:5d1f:56d4 with SMTP id d2e1a72fcca58-84fdc7c6a2fmr12528000b3a.14.1786841685271; Sat, 15 Aug 2026 17:54:45 -0700 (PDT) Received: from bloom.localdomain ([2604:3d09:178e:e100::6868]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8517d0236a9sm1589202b3a.24.2026.08.15.17.54.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 15 Aug 2026 17:54:44 -0700 (PDT) From: Ivy Lopez To: Greg Kroah-Hartman , Takashi Iwai Cc: Kees Cook , Christophe JAILLET , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Ivy Lopez , syzbot+2280f1cca5e6b0c353e4@syzkaller.appspotmail.com Subject: [PATCH] usb: gadget: f_midi2: fix use-after-free in string attribute show path Date: Sat, 15 Aug 2026 18:54:33 -0600 Message-ID: <20260816005434.34018-1-skunkolee@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit f_midi2_opts_str_show() takes the string lock internally, but its callers dereference the opts->info. pointer before calling it, outside the lock. This races with f_midi2_opts_str_store(), which frees the old string under opts->lock when the attribute is written concurrently, the show path can read a pointer that gets freed before the lock inside str_show() is even taken. Change f_midi2_opts_str_show() to take a pointer to the string field, matching the existing pattern in f_midi2_opts_str_store(), and dereference it only after the lock is held. Update all three callers (iface_name, block name, and the EP string option macro) accordingly. Reported-by: syzbot+2280f1cca5e6b0c353e4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2280f1cca5e6b0c353e4 Signed-off-by: Ivy Lopez --- drivers/usb/gadget/function/f_midi2.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/usb/gadget/function/f_midi2.c b/drivers/usb/gadget/function/f_midi2.c index 19fdac024343..6bfd171b96a9 100644 --- a/drivers/usb/gadget/function/f_midi2.c +++ b/drivers/usb/gadget/function/f_midi2.c @@ -2178,13 +2178,13 @@ static ssize_t f_midi2_opts_bool_store(struct f_midi2_opts *opts, /* generic show/store for string */ static ssize_t f_midi2_opts_str_show(struct f_midi2_opts *opts, - const char *str, char *page) + const char **strp, char *page) { int result = 0; mutex_lock(&opts->lock); - if (str) - result = scnprintf(page, PAGE_SIZE, "%s\n", str); + if (*strp) + result = scnprintf(page, PAGE_SIZE, "%s\n", *strp); mutex_unlock(&opts->lock); return result; } @@ -2278,7 +2278,7 @@ static ssize_t f_midi2_block_opts_name_show(struct config_item *item, { struct f_midi2_block_opts *opts = to_f_midi2_block_opts(item); - return f_midi2_opts_str_show(opts->ep->opts, opts->info.name, page); + return f_midi2_opts_str_show(opts->ep->opts, &opts->info.name, page); } static ssize_t f_midi2_block_opts_name_store(struct config_item *item, @@ -2435,7 +2435,7 @@ static ssize_t f_midi2_ep_opts_##name##_show(struct config_item *item, \ char *page) \ { \ struct f_midi2_ep_opts *opts = to_f_midi2_ep_opts(item); \ - return f_midi2_opts_str_show(opts->opts, opts->info.name, page);\ + return f_midi2_opts_str_show(opts->opts, &opts->info.name, page);\ } \ \ static ssize_t f_midi2_ep_opts_##name##_store(struct config_item *item, \ @@ -2589,7 +2589,7 @@ static ssize_t f_midi2_opts_iface_name_show(struct config_item *item, { struct f_midi2_opts *opts = to_f_midi2_opts(item); - return f_midi2_opts_str_show(opts, opts->info.iface_name, page); + return f_midi2_opts_str_show(opts, &opts->info.iface_name, page); } static ssize_t f_midi2_opts_iface_name_store(struct config_item *item, -- 2.55.0