On Mon, 19 Sep 2022 10:30:54 +0200, Takashi Iwai wrote: > > On Sun, 18 Sep 2022 15:01:11 +0200, > Rondreis wrote: > > > > Hello, > > > > When fuzzing the Linux kernel driver v6.0-rc4, the following crash was > > triggered. > > > > HEAD commit: 7e18e42e4b280c85b76967a9106a13ca61c16179 > > git tree: upstream > > > > kernel config: https://pastebin.com/raw/xtrgsXP3 > > C reproducer: https://pastebin.com/raw/w2sdQWYj > > console output: https://pastebin.com/raw/Yyf7zw2d > > > > Basically, in the c reproducer, we use the gadget module to emulate > > attaching a USB device(vendor id: 0x1bc7, product id: 0x1206, with the > > midi function) and executing some simple sequence of system calls. > > To reproduce this crash, we utilize a third-party library to emulate > > the attaching process: https://github.com/linux-usb-gadgets/libusbgx. > > Just clone this repository, install it, and compile the c > > reproducer with ``` gcc crash.c -lusbgx -lconfig -o crash ``` will do > > the trick. > > > > I would appreciate it if you have any idea how to solve this bug. > > Could you try the patch below? It looks like a simple double-free in > the code. A more proper patch is below. Please give it a try. thanks, Takashi -- 8< -- From: Takashi Iwai <tiwai@xxxxxxx> Subject: [PATCH] ALSA: core: Fix double-free at snd_card_new() During the code change to add the support for devres-managed card instance, we put an explicit kfree(card) call at the error path in snd_card_new(). This is needed for the early error path before the card is initialized with the device, but is rather superfluous and causes a double-free at the error path after the card instance is initialized, as the destructor of the card object already contains a kfree() call. This patch fixes the double-free situation by removing the superfluous kfree(). Meanwhile we need to call kfree() explicitly for the early error path, so it's added there instead. Fixes: e8ad415b7a55 ("ALSA: core: Add managed card creation") Reported-by: Rondreis <linhaoguo86@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/CAB7eexL1zBnB636hwS27d-LdPYZ_R1-5fJS_h=ZbCWYU=UPWJg@xxxxxxxxxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> --- sound/core/init.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/sound/core/init.c b/sound/core/init.c index 193dae361fac..5377f94eb211 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -178,10 +178,8 @@ int snd_card_new(struct device *parent, int idx, const char *xid, return -ENOMEM; err = snd_card_init(card, parent, idx, xid, module, extra_size); - if (err < 0) { - kfree(card); - return err; - } + if (err < 0) + return err; /* card is freed by error handler */ *card_ret = card; return 0; @@ -233,7 +231,7 @@ int snd_devm_card_new(struct device *parent, int idx, const char *xid, card->managed = true; err = snd_card_init(card, parent, idx, xid, module, extra_size); if (err < 0) { - devres_free(card); + devres_free(card); /* in managed mode, we need to free manually */ return err; } @@ -297,6 +295,8 @@ static int snd_card_init(struct snd_card *card, struct device *parent, mutex_unlock(&snd_card_mutex); dev_err(parent, "cannot find the slot for index %d (range 0-%i), error: %d\n", idx, snd_ecards_limit - 1, err); + if (!card->managed) + kfree(card); /* manually free here, as no destructor called */ return err; } set_bit(idx, snd_cards_lock); /* lock it */ -- 2.35.3
