Message ID | EDBAAA0BBBA2AC4E9C8B6B81DEEE1D6915DFB0ED@dggeml505-mbs.china.huawei.com (mailing list archive) |
---|---|
State | Changes Requested |
Headers | show |
Series | [v3] scsi: avoid potential deadloop in iscsi_if_rx func | expand |
Friendly ping... On 2019/10/31 14:17, wubo (T) wrote: > From: Bo Wu <wubo40@huawei.com> > > 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 the request in do-loop. If the return of iscsi_if_send_reply > func return -EAGAIN all the time, one deadloop 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, > > Details of the special case which can cause deadloop: > > 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 > > Here, we add one limit of retry times in do-loop to avoid the deadloop. > > Signed-off-by: Bo Wu <wubo40@huawei.com> > Reviewed-by: Zhiqiang Liu <liuzhiqiang26@huawei.com> > Suggested-by: Lee Duncan <LDuncan@suse.com> > Suggested-by: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de> > --- > V3:replace the error with warning as suggested by Ulrich > V2:add some debug kernel message as suggested by Lee Duncan > > Thanks, > Bo Wu > > drivers/scsi/scsi_transport_iscsi.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c > index 417b868d8735..ed8d9709b9b9 100644 > --- a/drivers/scsi/scsi_transport_iscsi.c > +++ b/drivers/scsi/scsi_transport_iscsi.c > @@ -24,6 +24,8 @@ > > #define ISCSI_TRANSPORT_VERSION "2.0-870" > > +#define ISCSI_SEND_MAX_ALLOWED 10 > + > #define CREATE_TRACE_POINTS > #include <trace/events/iscsi.h> > > @@ -3682,6 +3684,7 @@ 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) || > @@ -3712,6 +3715,10 @@ iscsi_if_rx(struct sk_buff *skb) > break; > err = iscsi_if_send_reply(portid, nlh->nlmsg_type, > 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); > } > -- > 1.8.3.1 > > > . >
> 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 the request in do-loop. If the return of iscsi_if_send_reply > func return -EAGAIN all the time, one deadloop 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, Lee/Chris/Ulrich: Please review!
On 11/12/19 5:37 PM, Martin K. Petersen wrote: > >> 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 the request in do-loop. If the return of iscsi_if_send_reply >> func return -EAGAIN all the time, one deadloop 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, > > Lee/Chris/Ulrich: Please review! > I believe I already added my Reviewed-by tag. Do you mean past that? Perhaps I missed something.
On 11/12/19 5:37 PM, Martin K. Petersen wrote: > >> 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 the request in do-loop. If the return of iscsi_if_send_reply >> func return -EAGAIN all the time, one deadloop 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, > > Lee/Chris/Ulrich: Please review! > Okay, after looking again at the thread, I do have some additional feedback for the patch submitter. You should put your "changes in V2, V3, ..." above the patch line (the "-- " on a line by itself), not as part of the patch. Also, as long as you are making one last round of changes, please change "deadloop" to "deadlock" in your patch subject, as deadloop is not a word. Lastly, the "Suggested-by" lines you added are fine, but that generally means that person suggested the patch, not changes. For folks that suggest changes, it's up to them to say they like or do not like your changes after you make them, at which point they can add their "Reviewed-by" tag if they wish. Please feel free to send your patch to me directly, before publishing, if you would like a review before publishing again.
diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c index 417b868d8735..ed8d9709b9b9 100644 --- a/drivers/scsi/scsi_transport_iscsi.c +++ b/drivers/scsi/scsi_transport_iscsi.c @@ -24,6 +24,8 @@ #define ISCSI_TRANSPORT_VERSION "2.0-870" +#define ISCSI_SEND_MAX_ALLOWED 10 + #define CREATE_TRACE_POINTS #include <trace/events/iscsi.h> @@ -3682,6 +3684,7 @@ 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) || @@ -3712,6 +3715,10 @@ iscsi_if_rx(struct sk_buff *skb) break; err = iscsi_if_send_reply(portid, nlh->nlmsg_type, 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); }