2019-11-05 06:48:03

by Pan Bian

Subject: [PATCH] Input: cyttsp4_core: fix use after free bug

The device md->input is used after it is released. Setting the device
data to NULL is unnecessary as the device is never used again. Instead,
md->input should be assigned NULL to avoid accessing the freed memory
accidently. Besides, checking md->si against NULL is superfluous as it
points to a variable address, which cannot be NULL.

Signed-off-by: Pan Bian <[email protected]>
---
drivers/input/touchscreen/cyttsp4_core.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/input/touchscreen/cyttsp4_core.c b/drivers/input/touchscreen/cyttsp4_core.c
index 4b22d49a0f49..2cd5f835665e 100644
--- a/drivers/input/touchscreen/cyttsp4_core.c
+++ b/drivers/input/touchscreen/cyttsp4_core.c
@@ -1990,11 +1990,6 @@ static int cyttsp4_mt_probe(struct cyttsp4 *cd)

/* get sysinfo */
md->si = &cd->sysinfo;
- if (!md->si) {
- dev_err(dev, "%s: Fail get sysinfo pointer from core p=%p\n",
- __func__, md->si);
- goto error_get_sysinfo;
- }

rc = cyttsp4_setup_input_device(cd);
if (rc)
@@ -2004,8 +1999,7 @@ static int cyttsp4_mt_probe(struct cyttsp4 *cd)

error_init_input:
input_free_device(md->input);
-error_get_sysinfo:
- input_set_drvdata(md->input, NULL);
+ md->input = NULL;
error_alloc_failed:
dev_err(dev, "%s failed.\n", __func__);
return rc;
--
2.7.4

2019-11-13 01:05:54

by Dmitry Torokhov

Subject: Re: [PATCH] Input: cyttsp4_core: fix use after free bug

On Tue, Nov 05, 2019 at 02:46:19PM +0800, Pan Bian wrote:
> The device md->input is used after it is released. Setting the device
> data to NULL is unnecessary as the device is never used again. Instead,
> md->input should be assigned NULL to avoid accessing the freed memory
> accidently.

No, we are tearing up the device anyway, I'd leave it as it was, so I'll
drop this chunk and apply the rest.

Thank you.

--
Dmitry