2023-05-08 22:03:35

by Badhri Jagan Sridharan

Subject: [PATCH v1] usb: typec: altmodes/displayport: fix pin_assignment_show

This patch fixes negative indexing of buf array in pin_assignment_show
when get_current_pin_assignments returns 0 i.e. no compatible pin
assignments are found.

BUG: KASAN: use-after-free in pin_assignment_show+0x26c/0x33c
...
Call trace:
dump_backtrace+0x110/0x204
dump_stack_lvl+0x84/0xbc
print_report+0x358/0x974
kasan_report+0x9c/0xfc
__do_kernel_fault+0xd4/0x2d4
do_bad_area+0x48/0x168
do_tag_check_fault+0x24/0x38
do_mem_abort+0x6c/0x14c
el1_abort+0x44/0x68
el1h_64_sync_handler+0x64/0xa4
el1h_64_sync+0x78/0x7c
pin_assignment_show+0x26c/0x33c
dev_attr_show+0x50/0xc0

Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
Cc: [email protected]
Signed-off-by: Badhri Jagan Sridharan <[email protected]>
---
drivers/usb/typec/altmodes/displayport.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 8f3e884222ad..66de880b28d0 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -516,6 +516,10 @@ static ssize_t pin_assignment_show(struct device *dev,

mutex_unlock(&dp->lock);

+ /* get_current_pin_assignments can return 0 when no matching pin assignments are found */
+ if (len == 0)
+ len++;
+
buf[len - 1] = '\n';
return len;
}

base-commit: ac9a78681b921877518763ba0e89202254349d1b
--
2.40.1.521.gf1e218fcd8-goog

2023-05-09 12:42:23

by Heikki Krogerus

Subject: Re: [PATCH v1] usb: typec: altmodes/displayport: fix pin_assignment_show

On Mon, May 08, 2023 at 09:44:43PM +0000, Badhri Jagan Sridharan wrote:
> This patch fixes negative indexing of buf array in pin_assignment_show
> when get_current_pin_assignments returns 0 i.e. no compatible pin
> assignments are found.
>
> BUG: KASAN: use-after-free in pin_assignment_show+0x26c/0x33c
> ...
> Call trace:
> dump_backtrace+0x110/0x204
> dump_stack_lvl+0x84/0xbc
> print_report+0x358/0x974
> kasan_report+0x9c/0xfc
> __do_kernel_fault+0xd4/0x2d4
> do_bad_area+0x48/0x168
> do_tag_check_fault+0x24/0x38
> do_mem_abort+0x6c/0x14c
> el1_abort+0x44/0x68
> el1h_64_sync_handler+0x64/0xa4
> el1h_64_sync+0x78/0x7c
> pin_assignment_show+0x26c/0x33c
> dev_attr_show+0x50/0xc0
>
> Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
> Cc: [email protected]
> Signed-off-by: Badhri Jagan Sridharan <[email protected]>

Reviewed-by: Heikki Krogerus <[email protected]>

> ---
> drivers/usb/typec/altmodes/displayport.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index 8f3e884222ad..66de880b28d0 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -516,6 +516,10 @@ static ssize_t pin_assignment_show(struct device *dev,
>
> mutex_unlock(&dp->lock);
>
> + /* get_current_pin_assignments can return 0 when no matching pin assignments are found */
> + if (len == 0)
> + len++;
> +
> buf[len - 1] = '\n';
> return len;
> }

thanks,

--
heikki