From fed0aa7c6eaedc6c0d4e362fc91724aa47be4a7b Mon Sep 17 00:00:00 2001 From: Ivy Lopez Date: Sat, 15 Aug 2026 18:54:33 -0600 Subject: [PATCH] usb: gadget: f_midi2: fix use-after-free in string attribute show path 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 Cc: stable Closes: https://syzkaller.appspot.com/bug?extid=2280f1cca5e6b0c353e4 Signed-off-by: Ivy Lopez Reviewed-by: Takashi Iwai Link: https://patch.msgid.link/20260816005434.34018-1-skunkolee@gmail.com Signed-off-by: Greg Kroah-Hartman --- 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 e0b743dfaba5..5b8b18281989 100644 --- a/drivers/usb/gadget/function/f_midi2.c +++ b/drivers/usb/gadget/function/f_midi2.c @@ -2177,13 +2177,13 @@ 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; } @@ -2277,7 +2277,7 @@ 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, @@ -2434,7 +2434,7 @@ 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,