On Sun, Oct 02, 2022 at 09:40:47AM +0800, Duoming Zhou wrote:
>
> The function iscsit_handle_time2retain_timeout() is a timer handler that
> runs in an atomic context, but it calls "alloc_skb(0, GFP_KERNEL | ...)"
> that may sleep. As a result, the sleep-in-atomic-context bug will happen.
> The process is shown below:
>
> iscsit_handle_time2retain_timeout()
> iscsit_close_session()
> iscsit_free_connection_recovery_entries()
> iscsit_free_cmd()
> __iscsit_free_cmd()
> cxgbit_unmap_cmd()
> cxgbit_abort_conn()
> alloc_skb(0, GFP_KERNEL | ...) //may sleep
>
> This patch changes the gfp_t parameter of alloc_skb() from GFP_KERNEL to
> GFP_ATOMIC in order to mitigate the bug.
>
> Fixes: 1ae01724ae92 ("cxgbit: Abort the TCP connection in case of data out timeout")
> Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
> ---
> drivers/target/iscsi/cxgbit/cxgbit_cm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/target/iscsi/cxgbit/cxgbit_cm.c b/drivers/target/iscsi/cxgbit/cxgbit_cm.c
> index 3336d2b78bf..eb3da6d2c62 100644
> --- a/drivers/target/iscsi/cxgbit/cxgbit_cm.c
> +++ b/drivers/target/iscsi/cxgbit/cxgbit_cm.c
> @@ -697,7 +697,7 @@ __cxgbit_abort_conn(struct cxgbit_sock *csk, struct sk_buff *skb)
>
> void cxgbit_abort_conn(struct cxgbit_sock *csk)
> {
> - struct sk_buff *skb = alloc_skb(0, GFP_KERNEL | __GFP_NOFAIL);
> + struct sk_buff *skb = alloc_skb(0, GFP_ATOMIC | __GFP_NOFAIL);
>
> cxgbit_get_csk(csk);
> cxgbit_init_wr_wait(&csk->com.wr_wait);
> --
> 2.17.1
>
The last line in cxgbit_abort_conn is cxgbit_wait_for_reply() which
also should not be called in interrupt context.
Anyway this issue is not due to cxgbit, it is common for iSCSI itself:
iscsit_close_session()
iscsit_free_connection_recovery_entries()
iscsit_free_cmd()
transport_generic_free_cmd()
target_wait_free_cmd()
wait_for_completion_timeout()
IMHO, there is no reason to call iscsit_close_session in an atomic context.
I have two patches relaited Time2Retain timer. I will share them today.
BR,
Dmitry
