Messages in this thread Patch in this message | | | Subject | Re: [PATCH] TTY: n_gsm, fix false positive WARN_ON | From | xinhui <> | Date | Wed, 25 Nov 2015 14:32:51 +0800 |
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hi, Jiri This warning should blame on commit 5a640967 ("tty/n_gsm.c: fix a memory leak in gsmld_open()"). When gsm driver failed to activate one mux,there is memory leak. So I call this ->cleanup() to do the cleanup work. Seems I did not consider all cases.
I have one confusion. As there is field gsm->num to store the index of gsm_mux[]. so in gsm_cleanup_mux(), why we still use for-loop to find this mux?
In error handle path, for example, the call trace in this patch, as we failed to activate it and the gsm->num is invalid(and the value is 0). we can just modify the codes like below:
if(gsm_mux[gsm->num] == gsm) ....other work else return;
I think it would work, and the logic is correct. Or I just miss something important?
thanks xinhui
On 2015/11/25 00:54, Jiri Slaby wrote: > 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: e1eaea46bb40 ("tty: n_gsm line discipline") > Cc: stable <stable@vger.kernel.org> > Signed-off-by: Jiri Slaby <jslaby@suse.cz> > --- > drivers/tty/n_gsm.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > index c3fe026d3168..9aff37186246 100644 > --- a/drivers/tty/n_gsm.c > +++ b/drivers/tty/n_gsm.c > @@ -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. */ >
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