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SubjectRe: KASAN: invalid-free in snd_card_new
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.


thanks,

Takashi

---
--- 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;
}

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