* [PATCH] tty: n_gsm: add missing tty_kref_put
@ 2021-11-09 10:39 Pavel Skripkin
2021-11-09 17:33 ` Jiri Slaby
0 siblings, 1 reply; 3+ messages in thread
From: Pavel Skripkin @ 2021-11-09 10:39 UTC (permalink / raw)
To: gregkh, jirislaby, hdanton; +Cc: linux-kernel, Pavel Skripkin
My local syzbot instance hit memory leak in gsmld_attach_gsm(). The
reproducer injects allocation failure in tty_register_device(). After
this error only previous tty_register_device() calls unwinded, but not
tty_kref_get().
It leads to tty_struct leak, because ->close() won't be called in case
of ->open() failure and nothing puts tty reference.
Fixes: 0a360e8b65d6 ("tty: n_gsm: check error while registering tty devices")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
drivers/tty/n_gsm.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 1d92d2a84889..1cc3aec17d2d 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2394,6 +2394,8 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
for (i--; i >= 1; i--)
tty_unregister_device(gsm_tty_driver,
base + i);
+
+ tty_kref_put(gsm->tty);
return PTR_ERR(dev);
}
}
--
2.33.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] tty: n_gsm: add missing tty_kref_put
2021-11-09 10:39 [PATCH] tty: n_gsm: add missing tty_kref_put Pavel Skripkin
@ 2021-11-09 17:33 ` Jiri Slaby
2021-11-09 19:10 ` Pavel Skripkin
0 siblings, 1 reply; 3+ messages in thread
From: Jiri Slaby @ 2021-11-09 17:33 UTC (permalink / raw)
To: Pavel Skripkin, gregkh, hdanton; +Cc: linux-kernel
On 09. 11. 21, 11:39, Pavel Skripkin wrote:
> My local syzbot instance hit memory leak in gsmld_attach_gsm(). The
> reproducer injects allocation failure in tty_register_device(). After
> this error only previous tty_register_device() calls unwinded, but not
> tty_kref_get().
>
> It leads to tty_struct leak, because ->close() won't be called in case
> of ->open() failure and nothing puts tty reference.
I don't have time to check the n_gsm case now (like: are you talking
about tty->open/close or file_ops->open/close -- they behave
differently), but tty definitely calls close even if open fails.
> Fixes: 0a360e8b65d6 ("tty: n_gsm: check error while registering tty devices")
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---
> drivers/tty/n_gsm.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 1d92d2a84889..1cc3aec17d2d 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -2394,6 +2394,8 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
> for (i--; i >= 1; i--)
> tty_unregister_device(gsm_tty_driver,
> base + i);
> +
> + tty_kref_put(gsm->tty);
> return PTR_ERR(dev);
> }
> }
>
--
js
suse labs
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tty: n_gsm: add missing tty_kref_put
2021-11-09 17:33 ` Jiri Slaby
@ 2021-11-09 19:10 ` Pavel Skripkin
0 siblings, 0 replies; 3+ messages in thread
From: Pavel Skripkin @ 2021-11-09 19:10 UTC (permalink / raw)
To: Jiri Slaby, gregkh, hdanton; +Cc: linux-kernel
On 11/9/21 20:33, Jiri Slaby wrote:
> On 09. 11. 21, 11:39, Pavel Skripkin wrote:
>> My local syzbot instance hit memory leak in gsmld_attach_gsm(). The
>> reproducer injects allocation failure in tty_register_device(). After
>> this error only previous tty_register_device() calls unwinded, but not
>> tty_kref_get().
>>
>> It leads to tty_struct leak, because ->close() won't be called in case
>> of ->open() failure and nothing puts tty reference.
>
> I don't have time to check the n_gsm case now (like: are you talking
> about tty->open/close or file_ops->open/close -- they behave
> differently), but tty definitely calls close even if open fails.
>
Oh, I see now. I wasn't aware about this difference. Will do more
detailed analysis of reported leak. Thank you for pointing it out!
With regards,
Pavel Skripkin
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-11-09 10:39 [PATCH] tty: n_gsm: add missing tty_kref_put Pavel Skripkin
2021-11-09 17:33 ` Jiri Slaby
2021-11-09 19:10 ` Pavel Skripkin
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