On 08/15/2018 05:56 PM, Vincent Pelletier wrote:
> Fixes a use-after-free reported by KASAN when later
> iscsi_target_login_sess_out gets called and it tries to access
> conn->sess->se_sess:
>
> Disabling lock debugging due to kernel taint
> iSCSI Login timeout on Network Portal [::]:3260
> iSCSI Login negotiation failed.
> ==================================================================
> BUG: KASAN: use-after-free in iscsi_target_login_sess_out.cold.12+0x58/0xff [iscsi_target_mod]
> Read of size 8 at addr ffff880109d070c8 by task iscsi_np/980
>
> CPU: 1 PID: 980 Comm: iscsi_np Tainted: G O 4.17.8kasan.sess.connops+ #4
> Hardware name: To be filled by O.E.M. To be filled by O.E.M./Aptio CRB, BIOS 5.6.5 05/19/2014
> Call Trace:
> dump_stack+0x71/0xac
> print_address_description+0x65/0x22e
> ? iscsi_target_login_sess_out.cold.12+0x58/0xff [iscsi_target_mod]
> kasan_report.cold.6+0x241/0x2fd
> iscsi_target_login_sess_out.cold.12+0x58/0xff [iscsi_target_mod]
> iscsi_target_login_thread+0x1086/0x1710 [iscsi_target_mod]
> ? __sched_text_start+0x8/0x8
> ? iscsi_target_login_sess_out+0x250/0x250 [iscsi_target_mod]
> ? __kthread_parkme+0xcc/0x100
> ? parse_args.cold.14+0xd3/0xd3
> ? iscsi_target_login_sess_out+0x250/0x250 [iscsi_target_mod]
> kthread+0x1a0/0x1c0
> ? kthread_bind+0x30/0x30
> ret_from_fork+0x35/0x40
>
> Allocated by task 980:
> kasan_kmalloc+0xbf/0xe0
> kmem_cache_alloc_trace+0x112/0x210
> iscsi_target_login_thread+0x816/0x1710 [iscsi_target_mod]
> kthread+0x1a0/0x1c0
> ret_from_fork+0x35/0x40
>
> Freed by task 980:
> __kasan_slab_free+0x125/0x170
> kfree+0x90/0x1d0
> iscsi_target_login_thread+0x1577/0x1710 [iscsi_target_mod]
> kthread+0x1a0/0x1c0
> ret_from_fork+0x35/0x40
>
> The buggy address belongs to the object at ffff880109d06f00
> which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 456 bytes inside of
> 512-byte region [ffff880109d06f00, ffff880109d07100)
> The buggy address belongs to the page:
> page:ffffea0004274180 count:1 mapcount:0 mapping:0000000000000000 index:0x0 compound_mapcount: 0
> flags: 0x17fffc000008100(slab|head)
> raw: 017fffc000008100 0000000000000000 0000000000000000 00000001000c000c
> raw: dead000000000100 dead000000000200 ffff88011b002e00 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff880109d06f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff880109d07000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ffff880109d07080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff880109d07100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff880109d07180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ==================================================================
>
> Also, let idr_alloc return value through instead of replacing it with -ENOMEM,
> as it is already a negative value and caller checks sign, not exact value.
>
> Signed-off-by: Vincent Pelletier <plr.vincent@xxxxxxxxx>
> ---
> drivers/target/iscsi/iscsi_target_login.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
> index df81b2f7cad9..7337ff80394e 100644
> --- a/drivers/target/iscsi/iscsi_target_login.c
> +++ b/drivers/target/iscsi/iscsi_target_login.c
> @@ -296,10 +296,8 @@ static int iscsi_login_zero_tsih_s1(
> }
>
> ret = iscsi_login_set_conn_values(sess, conn, pdu->cid);
> - if (unlikely(ret)) {
> - kfree(sess);
> - return ret;
> - }
> + if (unlikely(ret))
> + goto free_sess;
> sess->init_task_tag = pdu->itt;
> memcpy(&sess->isid, pdu->isid, 6);
> sess->exp_cmd_sn = be32_to_cpu(pdu->cmdsn);
> @@ -349,6 +347,7 @@ static int iscsi_login_zero_tsih_s1(
> ISCSI_LOGIN_STATUS_NO_RESOURCES);
> pr_err("Unable to allocate memory for"
> " struct iscsi_sess_ops.\n");
> + ret = -ENOMEM;
> goto remove_idr;
> }
>
> @@ -356,6 +355,7 @@ static int iscsi_login_zero_tsih_s1(
> if (IS_ERR(sess->se_sess)) {
> iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_TARGET_ERR,
> ISCSI_LOGIN_STATUS_NO_RESOURCES);
> + ret = -ENOMEM;
> goto free_ops;
> }
>
> @@ -370,7 +370,7 @@ static int iscsi_login_zero_tsih_s1(
> free_sess:
> kfree(sess);
> conn->sess = NULL;
> - return -ENOMEM;
> + return ret;
> }
>
> static int iscsi_login_zero_tsih_s2(
>
Looks good now. Thanks.
Reviewed-by: Mike Christie <mchristi@xxxxxxxxxx>
Martin, this was made over that patch that was going through Mathew's
tree. I do not know exactly which one though. It is in next here
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/target/iscsi?id=ad86353cbddbb6f1c95072ead744d547a9ac8211
