[PATCH] staging/rtl8712: fix potential memory leak

[Bernard Zhao]

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@xxxxxxx patch upstream OK

Signed-off-by: Bernard Zhao <zhaojunkui2008@xxxxxxx>
Signed-off-by: Bernard Zhao <bernard@xxxxxxxx>
---
 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);
 		precvbuf++;
 	}
 	precvpriv->free_recv_buf_queue_cnt = NR_RECVBUFF;
-- 
2.33.1