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

From: Nicholas A. Bellinger
Date: Thu Jun 01 2017 - 02:21:39 EST


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 <baijiaju1990@xxxxxxx>
> ---
> 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;
}