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[4.14,1/2] hamradio: defer 6pack kfree after unregister_netdev

Message ID 20220428141032.1026227-1-ovidiu.panait@windriver.com
State Superseded
Headers show
Series [4.14,1/2] hamradio: defer 6pack kfree after unregister_netdev | expand

Commit Message

Ovidiu Panait April 28, 2022, 2:10 p.m. UTC 
From: Lin Ma <linma@zju.edu.cn>

commit 0b9111922b1f399aba6ed1e1b8f2079c3da1aed8 upstream.

There is a possible race condition (use-after-free) like below

 (USE)                       |  (FREE)
  dev_queue_xmit             |
   __dev_queue_xmit          |
    __dev_xmit_skb           |
     sch_direct_xmit         | ...
      xmit_one               |
       netdev_start_xmit     | tty_ldisc_kill
        __netdev_start_xmit  |  6pack_close
         sp_xmit             |   kfree
          sp_encaps          |
                             |

According to the patch "defer ax25 kfree after unregister_netdev", this
patch reorder the kfree after the unregister_netdev to avoid the possible
UAF as the unregister_netdev() is well synchronized and won't return if
there is a running routine.

Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Xu Jia <xujia39@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
---
These commits are part of CVE-2022-1195 patchset.
Reference: https://bugzilla.redhat.com/show_bug.cgi?id=2056381
[1] https://github.com/torvalds/linux/commit/3e0588c291d6ce225f2b891753ca41d45ba42469
[2] https://github.com/torvalds/linux/commit/b2f37aead1b82a770c48b5d583f35ec22aabb61e
[3] https://github.com/torvalds/linux/commit/0b9111922b1f399aba6ed1e1b8f2079c3da1aed8
[4] https://github.com/torvalds/linux/commit/81b1d548d00bcd028303c4f3150fa753b9b8aa71

Commits [1] and [2] are already present in 4.14-stable, this patchset includes
backports for [3] and [4] (clean cherry-picks from 5.10 stable).

 drivers/net/hamradio/6pack.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
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Patch

diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 3d5b2b4899ec..7ff1c6f7eea2 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -690,9 +690,11 @@  static void sixpack_close(struct tty_struct *tty)
 	del_timer_sync(&sp->tx_t);
 	del_timer_sync(&sp->resync_t);
 
-	/* Free all 6pack frame buffers. */
+	/* Free all 6pack frame buffers after unreg. */
 	kfree(sp->rbuff);
 	kfree(sp->xbuff);
+
+	free_netdev(sp->dev);
 }
 
 /* Perform I/O control on an active 6pack channel. */