drivers/edac/edac_mc_sysfs.c: poll timeout cannot be zero

If you do

  echo 0 > /sys/module/edac_core/parameters/edac_mc_poll_msec

the following stack trace is output because the edac module is not
designed to poll with a timeout of zero.

  WARNING: CPU: 12 PID: 0 at lib/list_debug.c:33 __list_add+0xac/0xc0()
  list_add corruption. prev->next should be next (ffff8808291dd1b8), but was           (null). (prev=ffff8808286fe3f8).
  Modules linked in: sg nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache cfg80211 rfkill x86_pkg_temp_thermal coretemp kvm_intel kvm ixgbe e1000e crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd iTCO_wdt ptp sb_edac iTCO_vendor_support pps_core mdio ipmi_devintf edac_core ioatdma microcode shpchp lpc_ich pcspkr i2c_i801 dca mfd_core ipmi_si wmi ipmi_msghandler nfsd auth_rpcgss nfs_acl lockd sunrpc xfs libcrc32c sd_mod sr_mod cdrom crc_t10dif crct10dif_common mgag200 syscopyarea sysfillrect sysimgblt isci i2c_algo_bit drm_kms_helper ttm drm libsas ahci libahci scsi_transport_sas libata i2c_core dm_mirror dm_region_hash dm_log dm_mod
  CPU: 12 PID: 0 Comm: swapper/12 Not tainted 3.13.0+ #1
  Hardware name: Intel Corporation LH Pass ........../SVRBD-ROW_T, BIOS SE5C600.86B.01.08.0003.022620131521 02/26/2013
  Call Trace:
   <IRQ>
    __list_add+0xac/0xc0
    __internal_add_timer+0xab/0x130
    internal_add_timer+0x17/0x40
    mod_timer_pinned+0xca/0x170
    intel_pstate_timer_func+0x28a/0x380
    call_timer_fn+0x36/0x100
    run_timer_softirq+0x1ff/0x2f0
    __do_softirq+0xf5/0x2e0
    irq_exit+0x10d/0x120
    smp_apic_timer_interrupt+0x45/0x60
    apic_timer_interrupt+0x6d/0x80
   <EOI>
    cpuidle_idle_call+0xb9/0x1f0
    arch_cpu_idle+0xe/0x30
    cpu_startup_entry+0x9e/0x240
    start_secondary+0x1e4/0x290

  kernel BUG at kernel/timer.c:1084!
  invalid opcode: 0000 [#1] SMP
  Modules linked in: sg nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache cfg80211 rfkill x86_pkg_temp_thermal coretemp kvm_intel kvm ixgbe e1000e crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd iTCO_wdt ptp sb_edac iTCO_vendor_support pps_core mdio ipmi_devintf edac_core ioatdma microcode shpchp lpc_ich pcspkr i2c_i801 dca mfd_core ipmi_si wmi ipmi_msghandler nfsd auth_rpcgss nfs_acl lockd sunrpc xfs libcrc32c sd_mod sr_mod cdrom crc_t10dif crct10dif_common mgag200 syscopyarea sysfillrect sysimgblt isci i2c_algo_bit drm_kms_helper ttm drm libsas ahci libahci scsi_transport_sas libata i2c_core dm_mirror dm_region_hash dm_log dm_mod
  CPU: 12 PID: 0 Comm: swapper/12 Tainted: G        W    3.13.0+ #1
  Hardware name: Intel Corporation LH Pass ........../SVRBD-ROW_T, BIOS SE5C600.86B.01.08.0003.022620131521 02/26/2013
  Call Trace:
   <IRQ>
    run_timer_softirq+0x245/0x2f0
    __do_softirq+0xf5/0x2e0
    irq_exit+0x10d/0x120
    smp_apic_timer_interrupt+0x45/0x60
    apic_timer_interrupt+0x6d/0x80
   <EOI>
    cpuidle_idle_call+0xb9/0x1f0
    arch_cpu_idle+0xe/0x30
    cpu_startup_entry+0x9e/0x240
    start_secondary+0x1e4/0x290
  RIP   cascade+0x93/0xa0

  WARNING: CPU: 36 PID: 1154 at kernel/workqueue.c:1461 __queue_delayed_work+0xed/0x1a0()
  Modules linked in: sg nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache cfg80211 rfkill x86_pkg_temp_thermal coretemp kvm_intel kvm ixgbe e1000e crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd iTCO_wdt ptp sb_edac iTCO_vendor_support pps_core mdio ipmi_devintf edac_core ioatdma microcode shpchp lpc_ich pcspkr i2c_i801 dca mfd_core ipmi_si wmi ipmi_msghandler nfsd auth_rpcgss nfs_acl lockd sunrpc xfs libcrc32c sd_mod sr_mod cdrom crc_t10dif crct10dif_common mgag200 syscopyarea sysfillrect sysimgblt isci i2c_algo_bit drm_kms_helper ttm drm libsas ahci libahci scsi_transport_sas libata i2c_core dm_mirror dm_region_hash dm_log dm_mod
  CPU: 36 PID: 1154 Comm: kworker/u481:3 Tainted: G        W    3.13.0+ #1
  Hardware name: Intel Corporation LH Pass ........../SVRBD-ROW_T, BIOS SE5C600.86B.01.08.0003.022620131521 02/26/2013
  Workqueue: edac-poller edac_mc_workq_function [edac_core]
  Call Trace:
    dump_stack+0x45/0x56
    warn_slowpath_common+0x7d/0xa0
    warn_slowpath_null+0x1a/0x20
    __queue_delayed_work+0xed/0x1a0
    queue_delayed_work_on+0x27/0x50
    edac_mc_workq_function+0x72/0xa0 [edac_core]
    process_one_work+0x17b/0x460
    worker_thread+0x11b/0x400
    kthread+0xd2/0xf0
    ret_from_fork+0x7c/0xb0

This patch adds a range check in the edac_mc_poll_msec code to check for 0.
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Doug Thompson <dougthompson@xmission.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/edac/edac_mc_sysfs.c

@@ -61,7 +61,7 @@ static int edac_set_poll_msec(const char *val, struct kernel_param *kp)
 	ret = kstrtol(val, 0, &l);
 	if (ret)
 		return ret;
-	if ((int)l != l)
+	if (!l || ((int)l != l))
 		return -EINVAL;
 	*((int *)kp->arg) = l;