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net: set initial device refcount to 1

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When adding CONFIG_PCPU_DEV_REFCNT, I forgot that the
initial net device refcount was 0.

When CONFIG_PCPU_DEV_REFCNT is not set, this means
the first dev_hold() triggers an illegal refcount
operation (addition on 0)

refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 1 at lib/refcount.c:25 refcount_warn_saturate+0x128/0x1a4

Fix is to change initial (and final) refcount to be 1.

Also add a missing kerneldoc piece, as reported by
Stephen Rothwell.

Fixes: 919067cc84 ("net: add CONFIG_PCPU_DEV_REFCNT")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Guenter Roeck <groeck@google.com>
Tested-by: Guenter Roeck <groeck@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2021-03-22 11:21:45 -07:00
committed by David S. Miller
parent 0ca99c84df
commit add2d73631
2 changed files with 7 additions and 3 deletions
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include/linux/netdevice.h
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@@ -1792,6 +1792,7 @@ enum netdev_ml_priv_type {
*
* @proto_down_reason: reason a netdev interface is held down
* @pcpu_refcnt: Number of references to this device
* @dev_refcnt: Number of references to this device
* @todo_list: Delayed register/unregister
* @link_watch_list: XXX: need comments on this one
*