[PATCH 3/3] [NETROM] zero length frame filtering in NetRom

[PATCH 3/3] [NETROM] zero length frame filtering in NetRom

[bernard pidoux]

A zero length frame filter was recently introduced in ROSE protocole.
Previous commit makes the same at AX25 protocole level.
This patch has the same purpose for NetRom  protocole.
The reason is that empty frames have no meaning in NetRom protocole.

Signed-off-by: Bernard Pidoux <f6bvp@amsat.org>
---
 net/netrom/af_netrom.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index e9c05b8..ec6c898 100644
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -1037,6 +1037,10 @@ static int nr_sendmsg(struct kiocb *iocb, struct socket *sock,
 	unsigned char *asmptr;
 	int size;
 
+	/* Netrom empty data frame has no meaning : don't send */
+	if (len == 0)
+		return 0;
+
 	if (msg->msg_flags & ~(MSG_DONTWAIT|MSG_EOR|MSG_CMSG_COMPAT))
 		return -EINVAL;
 
@@ -1167,6 +1171,11 @@ static int nr_recvmsg(struct kiocb *iocb, struct socket *sock,
 	skb_reset_transport_header(skb);
 	copied     = skb->len;
 
+	/* NetRom empty data frame has no meaning : ignore it */
+	if (copied == 0) {
+		goto out;
+	}
+
 	if (copied > size) {
 		copied = size;
 		msg->msg_flags |= MSG_TRUNC;
@@ -1182,7 +1191,7 @@ static int nr_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	msg->msg_namelen = sizeof(*sax);
 
-	skb_free_datagram(sk, skb);
+out:	skb_free_datagram(sk, skb);
 
 	release_sock(sk);
 	return copied;
-- 
1.6.0.6

Re: [PATCH 3/3] [NETROM] zero length frame filtering in NetRom

[David Miller]

From: bernard pidoux <f6bvp@free.fr>
Date: Thu, 19 Mar 2009 19:18:52 +0100

> A zero length frame filter was recently introduced in ROSE protocole.
> Previous commit makes the same at AX25 protocole level.
> This patch has the same purpose for NetRom  protocole.
> The reason is that empty frames have no meaning in NetRom protocole.
> 
> Signed-off-by: Bernard Pidoux <f6bvp@amsat.org>

Applied.

swapper Not tainted 2.6.29.6

[Bernard Pidoux F6BVP]

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Running kernel 2.6.29.6 compiled without SMP option there was a kernel panic.
I don't know if it is related to  /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
or to AX25 module or a configuration problem.

Here is the netconsole capture.




[-- Attachment #2: nc_u_l_p_6666 --]
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BUG: unable to handle kernel paging request at ffff880004c90648
IP: [<ffffffff80249451>] del_timer+0x11/0xb0
PGD 202063 PUD 206063 PMD 7e2067 PTE 4c90160
Oops: 0002 [#1] DEBUG_PAGEALLOC
last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
CPU 0 
Modules linked in: netconsole netrom mkiss rose ax25 nfsd exportfs nfs lockd nfs_acl auth_rpcgss sunrpc af_packet ipv6 snd_via82xx snd_ac97_codec ac97_bus snd_mpu401_uart snd_rawmidi snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss snd_pcm i2c_viapro snd_timer snd_page_alloc snd_mixer_oss snd i2c_core soundcore sr_mod 8139cp 8139too mii shpchp pci_hotplug binfmt_misc ext3 jbd cpufreq_ondemand cpufreq_conservative cpufreq_powersave acpi_cpufreq freq_table floppy sg rtc_cmos thermal via_agp processor evdev button pata_via ata_generic ide_pci_generic pata_acpi sata_via libata sd_mod scsi_mod crc_t10dif
Pid: 0, comm: swapper Not tainted 2.6.29.6-nosmp #8 MS-7258
RIP: 0010:[<ffffffff80249451>]  [<ffffffff80249451>] del_timer+0x11/0xb0
RSP: 0018:ffffffff80717e00  EFLAGS: 00010246
RAX: ffffffff8067f0b8 RBX: ffff880004c90400 RCX: 0000000000000058
RDX: ffffe200009cb3d8 RSI: ffffffff8067f060 RDI: ffff880004c90618
RBP: ffffffff80717e20 R08: 0000000000000001 R09: 0000000000000490
R10: 0000000000000002 R11: ffffffff8067f008 R12: ffff880004c90618
R13: ffff880004c90400 R14: 0000000000000000 R15: ffffffff80717ed0
FS:  0000000000000000(0000) GS:ffffffff80720000(0000) knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: ffff880004c90648 CR3: 0000000074843000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process swapper (pid: 0, threadinfo ffffffff8068c000, task ffffffff80632360)
Stack:
 ffff880004c90400 ffff880004c90400 ffff880004c90400 ffffffffa035bb30
 ffffffff80717e30 ffffffffa035b850 ffffffff80717e60 ffffffffa035edb4
 ffff880004c90400 ffff880004c90400 0000000000000000 ffffffffa035bb30
Call Trace:
 <IRQ> <0> [<ffffffffa035bb30>] ? ax25_heartbeat_expiry+0x0/0x60 [ax25]
 [<ffffffffa035b850>] ax25_stop_heartbeat+0x10/0x20 [ax25]
 [<ffffffffa035edb4>] ax25_destroy_socket+0x64/0x210 [ax25]
 [<ffffffffa035bb30>] ? ax25_heartbeat_expiry+0x0/0x60 [ax25]
 [<ffffffffa035b045>] ax25_std_heartbeat_expiry+0xf5/0x100 [ax25]
 [<ffffffff80217c56>] ? read_tsc+0x16/0x40
 [<ffffffffa035bb55>] ax25_heartbeat_expiry+0x25/0x60 [ax25]
 [<ffffffff8024976c>] run_timer_softirq+0x15c/0x230
 [<ffffffff8025f8ff>] ? clockevents_program_event+0x4f/0x90
 [<ffffffff8024506c>] __do_softirq+0x7c/0x110
 [<ffffffff8021271c>] call_softirq+0x1c/0x30
 [<ffffffff8021407d>] do_softirq+0x5d/0xa0
 [<ffffffff80244c95>] irq_exit+0x45/0x50
 [<ffffffff80223e85>] smp_apic_timer_interrupt+0x55/0x90
 [<ffffffff80212253>] apic_timer_interrupt+0x13/0x20
 <EOI> <0> [<ffffffff80218afd>] ? mwait_idle+0x5d/0x70
 [<ffffffff8020fdd2>] ? enter_idle+0x22/0x30
 [<ffffffff8020fe2e>] ? cpu_idle+0x4e/0x80
 [<ffffffff804eb5cd>] ? rest_init+0x5d/0x70
Code: 10 18 00 00 eb a6 0f 1f 40 00 48 0f b6 c2 48 c1 e0 04 48 8d 54 07 10 eb 93 90 55 48 89 e5 41 56 45 31 f6 41 55 41 54 49 89 fc 53 <48> c7 47 30 00 00 00 00 48 83 3f 00 75 16 eb 76 0f 1f 80 00 00 
RIP  [<ffffffff80249451>] del_timer+0x11/0xb0
 RSP <ffffffff80717e00>
CR2: ffff880004c90648
---[ end trace 366e8cf762bbf316 ]---
Kernel panic - not syncing: Fatal exception in interrupt
Rebooting in 60 seconds..