linux-kernel - Re: [PATCH] staging/rtl8712: fix potential memory leak

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Date:   Wed, 11 May 2022 13:43:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Bernard Zhao <zhaojunkui2008@....com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Florian Schilhabel <florian.c.schilhabel@...glemail.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Bernard Zhao <bernard@...o.com>
Subject: Re: [PATCH] staging/rtl8712: fix potential memory leak

On Wed, May 11, 2022 at 04:21:44AM -0700, Bernard Zhao wrote:
> This bug is found by google syzbot, the link is:
> https://syzkaller.appspot.com/bug?id=3a325b8389fc41c1bc94de0f4ac437ed13cce584
> memory leak log:
> BUG: memory leak
> unreferenced object 0xffff88810ff9b3c0 (size 192):
>   comm "kworker/0:2", pid 3653, jiffies 4294942228 (age 8.250s)
>   hex dump (first 32 bytes):
>     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 d8 b3 f9 0f 81 88 ff ff  ................
>   backtrace:
>     [<00000000e0748eb7>] usb_alloc_urb+0x66/0xe0
>     [<00000000fe5a9432>] r8712_os_recvbuf_resource_alloc+0x1b/0x80
>     [<00000000923fed72>] r8712_init_recv_priv+0x96/0x210
>     [<000000000038512f>] _r8712_init_recv_priv+0x134/0x150
>     [<0000000066e70a4e>] r8712_init_drv_sw+0xa0/0x1d0
>     [<000000001d2974c0>] r871xu_drv_init.cold+0x104/0x7d1
>     [<000000001d449ce2>] usb_probe_interface+0x177/0x370
>     [<00000000cd123d34>] really_probe+0x159/0x4a0
>     [<00000000364585cc>] driver_probe_device+0x84/0x100
>     [<0000000048b74bde>] __device_attach_driver+0xee/0x110
>     [<00000000c358ab15>] bus_for_each_drv+0xb7/0x100
>     [<00000000bfa9b076>] __device_attach+0x122/0x250
>     [<0000000048fe302a>] bus_probe_device+0xc6/0xe0
>     [<000000002ceae175>] device_add+0x5be/0xc30
>     [<00000000e4813a0d>] usb_set_configuration+0x9d9/0xb90
>     [<00000000cbb8c98f>] usb_generic_driver_probe+0x8c/0xc0
> 
> For this issue，I see that the following call sequence causing
> some memory leaks:
> usb_probe_interface
>  r871xu_drv_init
>   r8712_init_drv_sw
>    _r8712_init_recv_priv
>     r8712_init_recv_priv//void type function
>      for (i = 0; i < NR_RECVBUFF;
>       if (r8712_os_recvbuf_resource_alloc(padapter, precvbuf))
>        r8712_os_recvbuf_resource_alloc
>         precvbuf->purb = usb_alloc_urb
>          kmalloc
> 
>        break;// if error branch. Here may be some memory leak,
>              // break directly after r8712_os_recvbuf_resource_alloc
>              // fail, and no cleanup operation is done.
> 
> And also the size of the memory leak can be seen in the log is
> 192 bytes, I check the size of the usb_alloc_urb application is
> usb_alloc_urb(0,
>  -> kmalloc(struct_size(urb, iso_frame_desc, iso_packets))
>   -> sizeof(struct urb)+iso_packets*sizeof(struct iso_frame_desc)
> iso_packets is 0, so the size of the actual application is
> sizeof(struct urb) -> the calculation result is 192, which matches
> the size of the leak point.
> 
> After that cleanup, the precvbuf->purb maybe used for long time
> So I add kmemleak_not_leak to avoid false positive report.
> 
> This patch syzbot test OK:
> 2022/05/11 06:15 14m zhaojunkui2008@....com patch upstream OK
> 
> Signed-off-by: Bernard Zhao <zhaojunkui2008@....com>
> Signed-off-by: Bernard Zhao <bernard@...o.com>

You can not sign off on the same patch by the same person multiple times
as this is a legal statement.

> ---
>  drivers/staging/rtl8712/rtl8712_recv.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/rtl8712/rtl8712_recv.c b/drivers/staging/rtl8712/rtl8712_recv.c
> index 0ffb30f1af7e..8bf8e6d5b005 100644
> --- a/drivers/staging/rtl8712/rtl8712_recv.c
> +++ b/drivers/staging/rtl8712/rtl8712_recv.c
> @@ -19,6 +19,7 @@
>  #include <linux/if_ether.h>
>  #include <linux/ip.h>
>  #include <net/cfg80211.h>
> +#include <linux/kmemleak.h>
>  
>  #include "osdep_service.h"
>  #include "drv_types.h"
> @@ -51,12 +52,20 @@ void r8712_init_recv_priv(struct recv_priv *precvpriv,
>  	for (i = 0; i < NR_RECVBUFF; i++) {
>  		INIT_LIST_HEAD(&precvbuf->list);
>  		spin_lock_init(&precvbuf->recvbuf_lock);
> -		if (r8712_os_recvbuf_resource_alloc(padapter, precvbuf))
> +		if (r8712_os_recvbuf_resource_alloc(padapter, precvbuf)) {
> +			int j = i;
> +
> +			while (j-- > 0) {
> +				r8712_os_recvbuf_resource_free(padapter, precvbuf);
> +				precvbuf--;
> +			}
>  			break;
> +		}
>  		precvbuf->ref_cnt = 0;
>  		precvbuf->adapter = padapter;
>  		list_add_tail(&precvbuf->list,
>  			      &(precvpriv->free_recv_buf_queue.queue));
> +		kmemleak_not_leak(precvbuf->purb);

This should not be needed, that's an indication that something is really
wrong in the driver.  Where is the urb really freed?

You should not have to say that this urb has not leaked if it really has
not leaked.  Clean it up properly if it needs to be cleaned up here, but
that's not usually where an urb is cleaned up at all.

This feels wrong, sorry.

thanks,

greg k-h