2018-08-23 20:39:22

by Laura Abbott

Subject: [PATCHv2] iscsi-target: Don't use stack buffer for scatterlist

Fedora got a bug report of a crash with iSCSI:

kernel BUG at include/linux/scatterlist.h:143!
...
RIP: 0010:iscsit_do_crypto_hash_buf+0x154/0x180 [iscsi_target_mod]
...
Call Trace:
? iscsi_target_tx_thread+0x200/0x200 [iscsi_target_mod]
iscsit_get_rx_pdu+0x4cd/0xa90 [iscsi_target_mod]
? native_sched_clock+0x3e/0xa0
? iscsi_target_tx_thread+0x200/0x200 [iscsi_target_mod]
iscsi_target_rx_thread+0x81/0xf0 [iscsi_target_mod]
kthread+0x120/0x140
? kthread_create_worker_on_cpu+0x70/0x70
ret_from_fork+0x3a/0x50

This is a BUG_ON for using a stack buffer with a scatterlist.
There are two cases that trigger this bug. Switch to using a
dynamically allocated buffer for one case and do not assign
a NULL buffer in another case.

Signed-off-by: Laura Abbott <[email protected]>
---
v2: Change the returns to breaks to avoid leaking memory
---
drivers/target/iscsi/iscsi_target.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 8e223799347a..086372e87cc6 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -1419,7 +1419,8 @@ static void iscsit_do_crypto_hash_buf(struct ahash_request *hash,

sg_init_table(sg, ARRAY_SIZE(sg));
sg_set_buf(sg, buf, payload_length);
- sg_set_buf(sg + 1, pad_bytes, padding);
+ if (padding)
+ sg_set_buf(sg + 1, pad_bytes, padding);

ahash_request_set_crypt(hash, sg, data_crc, payload_length + padding);

@@ -3913,10 +3914,14 @@ static bool iscsi_target_check_conn_state(struct iscsi_conn *conn)
static void iscsit_get_rx_pdu(struct iscsi_conn *conn)
{
int ret;
- u8 buffer[ISCSI_HDR_LEN], opcode;
+ u8 *buffer, opcode;
u32 checksum = 0, digest = 0;
struct kvec iov;

+ buffer = kmalloc_array(ISCSI_HDR_LEN, sizeof(*buffer), GFP_KERNEL);
+ if (!buffer)
+ return;
+
while (!kthread_should_stop()) {
/*
* Ensure that both TX and RX per connection kthreads
@@ -3933,7 +3938,7 @@ static void iscsit_get_rx_pdu(struct iscsi_conn *conn)
ret = rx_data(conn, &iov, 1, ISCSI_HDR_LEN);
if (ret != ISCSI_HDR_LEN) {
iscsit_rx_thread_wait_for_tcp(conn);
- return;
+ break;
}

if (conn->conn_ops->HeaderDigest) {
@@ -3943,7 +3948,7 @@ static void iscsit_get_rx_pdu(struct iscsi_conn *conn)
ret = rx_data(conn, &iov, 1, ISCSI_CRC_LEN);
if (ret != ISCSI_CRC_LEN) {
iscsit_rx_thread_wait_for_tcp(conn);
- return;
+ break;
}

iscsit_do_crypto_hash_buf(conn->conn_rx_hash, buffer,
@@ -3967,7 +3972,7 @@ static void iscsit_get_rx_pdu(struct iscsi_conn *conn)
}

if (conn->conn_state == TARG_CONN_STATE_IN_LOGOUT)
- return;
+ break;

opcode = buffer[0] & ISCSI_OPCODE_MASK;

@@ -3978,13 +3983,15 @@ static void iscsit_get_rx_pdu(struct iscsi_conn *conn)
" while in Discovery Session, rejecting.\n", opcode);
iscsit_add_reject(conn, ISCSI_REASON_PROTOCOL_ERROR,
buffer);
- return;
+ break;
}

ret = iscsi_target_rx_opcode(conn, buffer);
if (ret < 0)
- return;
+ break;
}
+
+ kfree(buffer);
}

int iscsi_target_rx_thread(void *arg)
--
2.17.1

2018-08-30 11:21:25

by Martin K. Petersen

Subject: Re: [PATCHv2] iscsi-target: Don't use stack buffer for scatterlist

> Fedora got a bug report of a crash with iSCSI:
>
> kernel BUG at include/linux/scatterlist.h:143!
> ...
> RIP: 0010:iscsit_do_crypto_hash_buf+0x154/0x180 [iscsi_target_mod]
> ...
> Call Trace:
> ? iscsi_target_tx_thread+0x200/0x200 [iscsi_target_mod]
> iscsit_get_rx_pdu+0x4cd/0xa90 [iscsi_target_mod]
> ? native_sched_clock+0x3e/0xa0
> ? iscsi_target_tx_thread+0x200/0x200 [iscsi_target_mod]
> iscsi_target_rx_thread+0x81/0xf0 [iscsi_target_mod]
> kthread+0x120/0x140
> ? kthread_create_worker_on_cpu+0x70/0x70
> ret_from_fork+0x3a/0x50
>
> This is a BUG_ON for using a stack buffer with a scatterlist. There
> are two cases that trigger this bug. Switch to using a dynamically
> allocated buffer for one case and do not assign a NULL buffer in
> another case.

Mike: Please review. Thanks!

--
Martin K. Petersen Oracle Linux Engineering