Hello.
On 10/24/2015 2:09 AM, Sergei Shtylyov 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 | 3 +++
1 file changed, 3 insertions(+)
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
@@ -1502,6 +1502,8 @@ static int sh_eth_rx(struct net_device *
phys_to_virt(ALIGN(rxdesc->addr, 4)),
pkt_len + 2);
skb = mdp->rx_skbuff[entry];
+ if (!skb)
+ goto skip;
mdp->rx_skbuff[entry] = NULL;
if (mdp->cd->rpadir)
skb_reserve(skb, NET_IP_ALIGN);
@@ -1516,6 +1518,7 @@ static int sh_eth_rx(struct net_device *
if (desc_status & RD_RFS8)
ndev->stats.multicast++;
}
+skip:
entry = (++mdp->cur_rx) % mdp->num_rx_ring;
rxdesc = &mdp->rx_ring[entry];
}
In fact, it could be done without goto/label. I'll recast.
MBR, Sergei
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