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TTY: n_gsm, fix false positive WARN_ON 

Dmitry reported, that the current cleanup code in n_gsm can trigger a
warning:
WARNING: CPU: 2 PID: 24238 at drivers/tty/n_gsm.c:2048 gsm_cleanup_mux+0x166/0x6b0()
...
Call Trace:
...
 [<ffffffff81247ab9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:490
 [<ffffffff828d0456>] gsm_cleanup_mux+0x166/0x6b0 drivers/tty/n_gsm.c:2048
 [<ffffffff828d4d87>] gsmld_open+0x5b7/0x7a0 drivers/tty/n_gsm.c:2386
 [<ffffffff828b9078>] tty_ldisc_open.isra.2+0x78/0xd0 drivers/tty/tty_ldisc.c:447
 [<ffffffff828b973a>] tty_set_ldisc+0x1ca/0xa70 drivers/tty/tty_ldisc.c:567
 [<     inline     >] tiocsetd drivers/tty/tty_io.c:2650
 [<ffffffff828a14ea>] tty_ioctl+0xb2a/0x2140 drivers/tty/tty_io.c:2883
...

But this is a legal path when open fails to find a space in the
gsm_mux array and tries to clean up. So make it a standard test
instead of a warning.

Reported-by: "Dmitry Vyukov" <dvyukov@google.com>
Cc: Alan Cox <alan@linux.intel.com>
Link: http://lkml.kernel.org/r/CACT4Y+bHQbAB68VFi7Romcs-Z9ZW3kQRvcq+BvHH1oa5NcAdLA@mail.gmail.com
Fixes: 5a640967 ("tty/n_gsm.c: fix a memory leak in gsmld_open()")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby 2016-03-22 18:09:51 +01:00 committed by Greg Kroah-Hartman
parent 6f210c18c1
commit d175feca89
1 changed files with 3 additions and 1 deletions
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4
drivers/tty/n_gsm.c
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@ -2045,7 +2045,9 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm)
}
}
spin_unlock(&gsm_mux_lock);
WARN_ON(i == MAX_MUX);
/* open failed before registering => nothing to do */
if (i == MAX_MUX)
return;
/* In theory disconnecting DLCI 0 is sufficient but for some
modems this is apparently not the case. */