Re: [PATCH] usb: typec: ucsi: Fix connector status writing past buffer size

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Tue, Dec 03, 2024 at 12:00:10PM -0800, Lucas De Marchi wrote:
> Similar to commit 65c4c9447bfc ("usb: typec: ucsi: Fix a missing bits to
> bytes conversion in ucsi_init()"), there was a missing conversion from
> bits to bytes. Here the outcome is worse though: since the value is
> lower than UCSI_MAX_DATA_LENGTH, instead of bailing out with an error,
> it writes past the buffer size.
> 
> The error is then seen in other places like below:
> 
> 	Oops: general protection fault, probably for non-canonical address 0x891e812cd0ed968: 0000 [#1] PREEMPT SMP NOPTI
> 	CPU: 3 UID: 110 PID: 906 Comm: prometheus-node Not tainted 6.13.0-rc1-xe #1
> 	Hardware name: Intel Corporation Lunar Lake Client Platform/LNL-M LP5 RVP1, BIOS LNLMFWI1.R00.3222.D84.2410171025 10/17/2024
> 	RIP: 0010:power_supply_get_property+0x3e/0xe0
> 	Code: 85 c0 7e 4f 4c 8b 07 89 f3 49 89 d4 49 8b 48 20 48 85 c9 74 72 49 8b 70 18 31 d2 31 c0 eb 0b 83 c2 01 48 63 c2 48 39 c8 73 5d <3b> 1c 86 75 f0 49 8b 40 28 4c 89 e2 89 de ff d0 0f 1f 00 5b 41 5c
> 	RSP: 0018:ffffc900017dfa50 EFLAGS: 00010246
> 	RAX: 0000000000000000 RBX: 0000000000000011 RCX: c963b02c06092008
> 	RDX: 0000000000000000 RSI: 0891e812cd0ed968 RDI: ffff888121dd6800
> 	RBP: ffffc900017dfa68 R08: ffff88810a4024b8 R09: 0000000000000000
> 	R10: 0000000000000000 R11: 0000000000000000 R12: ffffc900017dfa78
> 	R13: ffff888121dd6800 R14: ffff888138ad2c00 R15: ffff88810c57c528
> 	FS:  00007713a2ffd6c0(0000) GS:ffff88846f380000(0000) knlGS:0000000000000000
> 	CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> 	CR2: 000000c0004b1000 CR3: 0000000121ce8003 CR4: 0000000000f72ef0
> 	DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> 	DR3: 0000000000000000 DR6: 00000000ffff07f0 DR7: 0000000000000400
> 	PKRU: 55555554
> 	Call Trace:
> 	 <TASK>
> 	 ? show_regs+0x6c/0x80
> 	 ? die_addr+0x37/0xa0
> 	 ? exc_general_protection+0x1c1/0x440
> 	 ? asm_exc_general_protection+0x27/0x30
> 	 ? power_supply_get_property+0x3e/0xe0
> 	 power_supply_hwmon_read+0x50/0xe0
> 	 hwmon_attr_show+0x46/0x170
> 	 dev_attr_show+0x1a/0x70
> 	 sysfs_kf_seq_show+0xaa/0x120
> 	 kernfs_seq_show+0x41/0x60
> 
> Just use the buffer size as argument to fix it.
> 
> Fixes: 226ff2e681d0 ("usb: typec: ucsi: Convert connector specific commands to bitmaps")
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/usb/typec/ucsi/ucsi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index c435c0835744a..69caae84879e9 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -651,7 +651,8 @@ static void ucsi_unregister_altmodes(struct ucsi_connector *con, u8 recipient)
>  static int ucsi_get_connector_status(struct ucsi_connector *con, bool conn_ack)
>  {
>  	u64 command = UCSI_GET_CONNECTOR_STATUS | UCSI_CONNECTOR_NUMBER(con->num);
> -	size_t size = min(UCSI_GET_CONNECTOR_STATUS_SIZE, UCSI_MAX_DATA_LENGTH(con->ucsi));
> +	size_t size = min(sizeof(con->status),
> +			  UCSI_MAX_DATA_LENGTH(con->ucsi));
>  	int ret;
>  
>  	ret = ucsi_send_command_common(con->ucsi, command, &con->status, size, conn_ack);
> -- 
> 2.47.0

-- 
heikki