From: Bo Wu wubo40@huawei.com
commit bba340c79bfe3644829db5c852fdfa9e33837d6d upstream.
In iscsi_if_rx func, after receiving one request through iscsi_if_recv_msg func, iscsi_if_send_reply will be called to try to reply to the request in a do-while loop. If the iscsi_if_send_reply function keeps returning -EAGAIN, a deadlock will occur.
For example, a client only send msg without calling recvmsg func, then it will result in the watchdog soft lockup. The details are given as follows:
sock_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ISCSI); retval = bind(sock_fd, (struct sock addr*) & src_addr, sizeof(src_addr); while (1) { state_msg = sendmsg(sock_fd, &msg, 0); //Note: recvmsg(sock_fd, &msg, 0) is not processed here. } close(sock_fd);
watchdog: BUG: soft lockup - CPU#7 stuck for 22s! [netlink_test:253305] Sample time: 4000897528 ns(HZ: 250) Sample stat: curr: user: 675503481560, nice: 321724050, sys: 448689506750, idle: 4654054240530, iowait: 40885550700, irq: 14161174020, softirq: 8104324140, st: 0 deta: user: 0, nice: 0, sys: 3998210100, idle: 0, iowait: 0, irq: 1547170, softirq: 242870, st: 0 Sample softirq: TIMER: 992 SCHED: 8 Sample irqstat: irq 2: delta 1003, curr: 3103802, arch_timer CPU: 7 PID: 253305 Comm: netlink_test Kdump: loaded Tainted: G OE Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 pstate: 40400005 (nZcv daif +PAN -UAO) pc : __alloc_skb+0x104/0x1b0 lr : __alloc_skb+0x9c/0x1b0 sp : ffff000033603a30 x29: ffff000033603a30 x28: 00000000000002dd x27: ffff800b34ced810 x26: ffff800ba7569f00 x25: 00000000ffffffff x24: 0000000000000000 x23: ffff800f7c43f600 x22: 0000000000480020 x21: ffff0000091d9000 x20: ffff800b34eff200 x19: ffff800ba7569f00 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0001000101000100 x13: 0000000101010000 x12: 0101000001010100 x11: 0001010101010001 x10: 00000000000002dd x9 : ffff000033603d58 x8 : ffff800b34eff400 x7 : ffff800ba7569200 x6 : ffff800b34eff400 x5 : 0000000000000000 x4 : 00000000ffffffff x3 : 0000000000000000 x2 : 0000000000000001 x1 : ffff800b34eff2c0 x0 : 0000000000000300 Call trace: __alloc_skb+0x104/0x1b0 iscsi_if_rx+0x144/0x12bc [scsi_transport_iscsi] netlink_unicast+0x1e0/0x258 netlink_sendmsg+0x310/0x378 sock_sendmsg+0x4c/0x70 sock_write_iter+0x90/0xf0 __vfs_write+0x11c/0x190 vfs_write+0xac/0x1c0 ksys_write+0x6c/0xd8 __arm64_sys_write+0x24/0x30 el0_svc_common+0x78/0x130 el0_svc_handler+0x38/0x78 el0_svc+0x8/0xc
Link: https://lore.kernel.org/r/EDBAAA0BBBA2AC4E9C8B6B81DEEE1D6915E3D4D2@dggeml505... Signed-off-by: Bo Wu wubo40@huawei.com Reviewed-by: Zhiqiang Liu liuzhiqiang26@huawei.com Reviewed-by: Lee Duncan lduncan@suse.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/scsi/scsi_transport_iscsi.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/drivers/scsi/scsi_transport_iscsi.c +++ b/drivers/scsi/scsi_transport_iscsi.c @@ -37,6 +37,8 @@
#define ISCSI_TRANSPORT_VERSION "2.0-870"
+#define ISCSI_SEND_MAX_ALLOWED 10 + static int dbg_session; module_param_named(debug_session, dbg_session, int, S_IRUGO | S_IWUSR); @@ -3695,6 +3697,7 @@ iscsi_if_rx(struct sk_buff *skb) struct nlmsghdr *nlh; struct iscsi_uevent *ev; uint32_t group; + int retries = ISCSI_SEND_MAX_ALLOWED;
nlh = nlmsg_hdr(skb); if (nlh->nlmsg_len < sizeof(*nlh) + sizeof(*ev) || @@ -3725,6 +3728,10 @@ iscsi_if_rx(struct sk_buff *skb) break; err = iscsi_if_send_reply(group, nlh->nlmsg_seq, nlh->nlmsg_type, 0, 0, ev, sizeof(*ev)); + if (err == -EAGAIN && --retries < 0) { + printk(KERN_WARNING "Send reply failed, error %d\n", err); + break; + } } while (err < 0 && err != -ECONNREFUSED && err != -ESRCH); skb_pull(skb, rlen); }