Re: [PATCH] iscsi: Fix a sleep-in-atomic bug

[Jia-Ju Bai]

On 06/01/2017 02:21 PM, Nicholas A. Bellinger wrote:

Hi Jia-Ju,

On Wed, 2017-05-31 at 11:26 +0800, Jia-Ju Bai wrote:

The driver may sleep under a spin lock, and the function call path is:
iscsit_tpg_enable_portal_group (acquire the lock by spin_lock)
   iscsi_update_param_value
     kstrdup(GFP_KERNEL) -->  may sleep

To fix it, the "GFP_KERNEL" is replaced with "GFP_ATOMIC".

Signed-off-by: Jia-Ju Bai<baijiaju1...@163.com>
---
  drivers/target/iscsi/iscsi_target_parameters.c |    2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

Btw, the use of tpg->tpg_state_lock in iscsit_tpg_enable_portal_group()
while checking existing state and calling iscsi_update_param_value() is
not necessary, since lio_target_tpg_enable_store() is already holding
iscsit_get_tpg() ->  tpg->tpg_access_lock.

How about the following instead to only take tpg->tpg_state_lock when
updating tpg->tpg_state instead..?

diff --git a/drivers/target/iscsi/iscsi_target_tpg.c 
b/drivers/target/iscsi/iscsi_target_tpg.c
index 2e7e08d..abaabba 100644
--- a/drivers/target/iscsi/iscsi_target_tpg.c
+++ b/drivers/target/iscsi/iscsi_target_tpg.c
@@ -311,11 +311,9 @@ int iscsit_tpg_enable_portal_group(struct 
iscsi_portal_group *tpg)
         struct iscsi_tiqn *tiqn = tpg->tpg_tiqn;
         int ret;

-       spin_lock(&tpg->tpg_state_lock);
         if (tpg->tpg_state == TPG_STATE_ACTIVE) {
                 pr_err("iSCSI target portal group: %hu is already"
                         " active, ignoring request.\n", tpg->tpgt);
-               spin_unlock(&tpg->tpg_state_lock);
                 return -EINVAL;
         }
         /*
@@ -324,10 +322,8 @@ int iscsit_tpg_enable_portal_group(struct 
iscsi_portal_group *tpg)
          * is enforced (as per default), and remove the NONE option.
          */
         param = iscsi_find_param_from_key(AUTHMETHOD, tpg->param_list);
-       if (!param) {
-               spin_unlock(&tpg->tpg_state_lock);
+       if (!param)
                 return -EINVAL;
-       }

         if (tpg->tpg_attrib.authentication) {
                 if (!strcmp(param->value, NONE)) {
@@ -341,6 +337,7 @@ int iscsit_tpg_enable_portal_group(struct 
iscsi_portal_group *tpg)
                         goto err;
         }

+       spin_lock(&tpg->tpg_state_lock);
         tpg->tpg_state = TPG_STATE_ACTIVE;
         spin_unlock(&tpg->tpg_state_lock);

@@ -353,7 +350,6 @@ int iscsit_tpg_enable_portal_group(struct 
iscsi_portal_group *tpg)
         return 0;

  err:
-       spin_unlock(&tpg->tpg_state_lock);
         return ret;
  }

I think it is fine to me.

Thanks,
Jia-Ju Bai