From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Subject: [PATCH RTF] sh_eth: fix kernel oops in skb_put() Date: Sat, 24 Oct 2015 02:09:47 +0300 Message-ID: <4859772.ltR2e4ZqZH@wasted.cogentembedded.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: linux-sh@vger.kernel.org To: netdev@vger.kernel.org, yashi@atmark-techno.com Return-path: Sender: linux-sh-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 Signed-off-by: Sergei Shtylyov --- 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]; }