Hello. On 10/27/2015 01:52 AM, Yasushi SHOJI wrote:
In a low memory situation the following kernel oops occurs: Unable to handle kernel NULL pointer dereference at virtual address 00000050 pgd = 8490c000 [00000050] *pgd=4651e831, *pte=00000000, *ppte=00000000 Internal error: Oops: 17 [#1] PREEMPT ARM Modules linked in: CPU: 0 Not tainted (3.4-at16 #9) PC is at skb_put+0x10/0x98 LR is at sh_eth_poll+0x2c8/0xa10 pc : [<8035f780>] lr : [<8028bf50>] psr: 60000113 sp : 84eb1a90 ip : 84eb1ac8 fp : 84eb1ac4 r10: 0000003f r9 : 000005ea r8 : 00000000 r7 : 00000000 r6 : 940453b0 r5 : 00030000 r4 : 9381b180 r3 : 00000000 r2 : 00000000 r1 : 000005ea r0 : 00000000 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user Control: 10c53c7d Table: 4248c059 DAC: 00000015 Process klogd (pid: 2046, stack limit = 0x84eb02e8) [...] This is because netdev_alloc_skb() fails and 'mdp->rx_skbuff[entry]' is left NULL but sh_eth_rx() later uses it without checking. Add such check... Reported-by: Yasushi SHOJI <ya...@atmark-techno.com> Signed-off-by: Sergei Shtylyov <sergei.shtyl...@cogentembedded.com> --- This patch is against DaveM's 'net.git' repo. drivers/net/ethernet/renesas/sh_eth.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: net/drivers/net/ethernet/renesas/sh_eth.c =================================================================== --- net.orig/drivers/net/ethernet/renesas/sh_eth.c +++ net/drivers/net/ethernet/renesas/sh_eth.c @@ -1481,6 +1481,7 @@ static int sh_eth_rx(struct net_device * if (mdp->cd->shift_rd0) desc_status >>= 16; + skb = mdp->rx_skbuff[entry]; if (desc_status & (RD_RFS1 | RD_RFS2 | RD_RFS3 | RD_RFS4 | RD_RFS5 | RD_RFS6 | RD_RFS10)) { ndev->stats.rx_errors++; @@ -1496,12 +1497,11 @@ static int sh_eth_rx(struct net_device * ndev->stats.rx_missed_errors++; if (desc_status & RD_RFS10) ndev->stats.rx_over_errors++; - } else { + } else if (skb) { if (!mdp->cd->hw_swap) sh_eth_soft_swap( phys_to_virt(ALIGN(rxdesc->addr, 4)), pkt_len + 2); - skb = mdp->rx_skbuff[entry]; mdp->rx_skbuff[entry] = NULL; if (mdp->cd->rpadir) skb_reserve(skb, NET_IP_ALIGN);This certainly prevents from a bad access, however, some odd thing is going on. Once I hit a low memory situation with this patch, network thorough-put and response is very bad.
telnet, ping, wget takes loong time. PING 172.16.2.13 (172.16.2.13) 56(84) bytes of data. 64 bytes from 172.16.2.13: icmp_seq=5 ttl=64 time=0.223 ms 64 bytes from 172.16.2.13: icmp_seq=6 ttl=64 time=0.195 ms 64 bytes from 172.16.2.13: icmp_seq=7 ttl=64 time=0.203 ms 64 bytes from 172.16.2.13: icmp_seq=8 ttl=64 time=0.219 ms 64 bytes from 172.16.2.13: icmp_seq=9 ttl=64 time=0.165 ms 64 bytes from 172.16.2.13: icmp_seq=10 ttl=64 time=0.171 ms 64 bytes from 172.16.2.13: icmp_seq=1 ttl=64 time=9023 ms 64 bytes from 172.16.2.13: icmp_seq=2 ttl=64 time=8022 ms 64 bytes from 172.16.2.13: icmp_seq=3 ttl=64 time=7014 ms 64 bytes from 172.16.2.13: icmp_seq=4 ttl=64 time=6006 ms I'll investigate it.
Shoji-san, can I push this patch to net.git? I doubt that it has ill effects in itself -- the reason of the slowdown you're seeing should be somewhere else...
MBR, Sergei -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
