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slcan: Fix double-free on slcan_open() error path

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Commit 9ebd796e2400 ("can: slcan: Fix use-after-free Read in
slcan_open") was incorrectly backported to 4.4 and 4.9 stable
branches.

Since they do not have commit cf124db566e6 ("net: Fix inconsistent
teardown and release of private netdev state."), the destructor
function slc_free_netdev() is already responsible for calling
free_netdev() and slcan_open() must not call both of them.

yangerkun previously fixed the same bug in slip.

Fixes: ce624b2089ea ("can: slcan: Fix use-after-free Read in slcan_open") # 4.4
Fixes: f59604a80fa4 ("slcan: not call free_netdev before rtnl_unlock ...") # 4.4
Fixes: 56635a1e6ffb ("can: slcan: Fix use-after-free Read in slcan_open") # 4.9
Fixes: a1c9b23142ac ("slcan: not call free_netdev before rtnl_unlock ...") # 4.9
Cc: yangerkun <yangerkun@huawei.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ben Hutchings 2020-06-02 18:54:18 +01:00 committed by Greg Kroah-Hartman
parent a7481f5f1a
commit f8535892e1
1 changed files with 1 additions and 2 deletions
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3
drivers/net/can/slcan.c
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@ -618,10 +618,9 @@ err_free_chan:
sl->tty = NULL;
tty->disc_data = NULL;
clear_bit(SLF_INUSE, &sl->flags);
slc_free_netdev(sl->dev);
/* do not call free_netdev before rtnl_unlock */
rtnl_unlock();
free_netdev(sl->dev);
slc_free_netdev(sl->dev);
return err;
err_exit: