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mikechristie
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scsi: iscsi_tcp: Fix UAF during logout when accessing the shost ipaddress
Bug report and analysis from Ding Hui. During iSCSI session logout, if another task accesses the shost ipaddress attr, we can get a KASAN UAF report like this: [ 276.942144] BUG: KASAN: use-after-free in _raw_spin_lock_bh+0x78/0xe0 [ 276.942535] Write of size 4 at addr ffff8881053b45b8 by task cat/4088 [ 276.943511] CPU: 2 PID: 4088 Comm: cat Tainted: G E 6.1.0-rc8+ #3 [ 276.943997] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 [ 276.944470] Call Trace: [ 276.944943] <TASK> [ 276.945397] dump_stack_lvl+0x34/0x48 [ 276.945887] print_address_description.constprop.0+0x86/0x1e7 [ 276.946421] print_report+0x36/0x4f [ 276.947358] kasan_report+0xad/0x130 [ 276.948234] kasan_check_range+0x35/0x1c0 [ 276.948674] _raw_spin_lock_bh+0x78/0xe0 [ 276.949989] iscsi_sw_tcp_host_get_param+0xad/0x2e0 [iscsi_tcp] [ 276.951765] show_host_param_ISCSI_HOST_PARAM_IPADDRESS+0xe9/0x130 [scsi_transport_iscsi] [ 276.952185] dev_attr_show+0x3f/0x80 [ 276.953005] sysfs_kf_seq_show+0x1fb/0x3e0 [ 276.953401] seq_read_iter+0x402/0x1020 [ 276.954260] vfs_read+0x532/0x7b0 [ 276.955113] ksys_read+0xed/0x1c0 [ 276.955952] do_syscall_64+0x38/0x90 [ 276.956347] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 276.956769] RIP: 0033:0x7f5d3a679222 [ 276.957161] Code: c0 e9 b2 fe ff ff 50 48 8d 3d 32 c0 0b 00 e8 a5 fe 01 00 0f 1f 44 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 48 83 ec 28 48 89 54 24 [ 276.958009] RSP: 002b:00007ffc864d16a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [ 276.958431] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f5d3a679222 [ 276.958857] RDX: 0000000000020000 RSI: 00007f5d3a4fe000 RDI: 0000000000000003 [ 276.959281] RBP: 00007f5d3a4fe000 R08: 00000000ffffffff R09: 0000000000000000 [ 276.959682] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000020000 [ 276.960126] R13: 0000000000000003 R14: 0000000000000000 R15: 0000557a26dada58 [ 276.960536] </TASK> [ 276.961357] Allocated by task 2209: [ 276.961756] kasan_save_stack+0x1e/0x40 [ 276.962170] kasan_set_track+0x21/0x30 [ 276.962557] __kasan_kmalloc+0x7e/0x90 [ 276.962923] __kmalloc+0x5b/0x140 [ 276.963308] iscsi_alloc_session+0x28/0x840 [scsi_transport_iscsi] [ 276.963712] iscsi_session_setup+0xda/0xba0 [libiscsi] [ 276.964078] iscsi_sw_tcp_session_create+0x1fd/0x330 [iscsi_tcp] [ 276.964431] iscsi_if_create_session.isra.0+0x50/0x260 [scsi_transport_iscsi] [ 276.964793] iscsi_if_recv_msg+0xc5a/0x2660 [scsi_transport_iscsi] [ 276.965153] iscsi_if_rx+0x198/0x4b0 [scsi_transport_iscsi] [ 276.965546] netlink_unicast+0x4d5/0x7b0 [ 276.965905] netlink_sendmsg+0x78d/0xc30 [ 276.966236] sock_sendmsg+0xe5/0x120 [ 276.966576] ____sys_sendmsg+0x5fe/0x860 [ 276.966923] ___sys_sendmsg+0xe0/0x170 [ 276.967300] __sys_sendmsg+0xc8/0x170 [ 276.967666] do_syscall_64+0x38/0x90 [ 276.968028] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 276.968773] Freed by task 2209: [ 276.969111] kasan_save_stack+0x1e/0x40 [ 276.969449] kasan_set_track+0x21/0x30 [ 276.969789] kasan_save_free_info+0x2a/0x50 [ 276.970146] __kasan_slab_free+0x106/0x190 [ 276.970470] __kmem_cache_free+0x133/0x270 [ 276.970816] device_release+0x98/0x210 [ 276.971145] kobject_cleanup+0x101/0x360 [ 276.971462] iscsi_session_teardown+0x3fb/0x530 [libiscsi] [ 276.971775] iscsi_sw_tcp_session_destroy+0xd8/0x130 [iscsi_tcp] [ 276.972143] iscsi_if_recv_msg+0x1bf1/0x2660 [scsi_transport_iscsi] [ 276.972485] iscsi_if_rx+0x198/0x4b0 [scsi_transport_iscsi] [ 276.972808] netlink_unicast+0x4d5/0x7b0 [ 276.973201] netlink_sendmsg+0x78d/0xc30 [ 276.973544] sock_sendmsg+0xe5/0x120 [ 276.973864] ____sys_sendmsg+0x5fe/0x860 [ 276.974248] ___sys_sendmsg+0xe0/0x170 [ 276.974583] __sys_sendmsg+0xc8/0x170 [ 276.974891] do_syscall_64+0x38/0x90 [ 276.975216] entry_SYSCALL_64_after_hwframe+0x63/0xcd We can easily reproduce by two tasks: 1. while :; do iscsiadm -m node --login; iscsiadm -m node --logout; done 2. while :; do cat \ /sys/devices/platform/host*/iscsi_host/host*/ipaddress; done iscsid | cat --------------------------------+--------------------------------------- |- iscsi_sw_tcp_session_destroy | |- iscsi_session_teardown | |- device_release | |- iscsi_session_release ||- dev_attr_show |- kfree | |- show_host_param_ | ISCSI_HOST_PARAM_IPADDRESS | |- iscsi_sw_tcp_host_get_param | |- r/w tcp_sw_host->session (UAF) |- iscsi_host_remove | |- iscsi_host_free | Fix the above bug by splitting the session removal into 2 parts: 1. removal from iSCSI class which includes sysfs and removal from host tracking. 2. freeing of session. During iscsi_tcp host and session removal we can remove the session from sysfs then remove the host from sysfs. At this point we know userspace is not accessing the kernel via sysfs so we can free the session and host. Link: https://lore.kernel.org/r/20230117193937.21244-2-michael.christie@oracle.com Signed-off-by: Mike Christie <michael.christie@oracle.com> Reviewed-by: Lee Duncan <lduncan@suse.com> Acked-by: Ding Hui <dinghui@sangfor.com.cn> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> (cherry picked from commit 6f1d64b) [Fixed to apply on 5.4] Signed-off-by: Puranjay Mohan <pjy@amazon.com>
1 parent 23ec323 commit acd2dcd

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3 files changed

+42
-9
lines changed

3 files changed

+42
-9
lines changed

‎drivers/scsi/iscsi_tcp.c

Lines changed: 9 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -895,10 +895,17 @@ static void iscsi_sw_tcp_session_destroy(struct iscsi_cls_session *cls_session)
895895
if (WARN_ON_ONCE(session->leadconn))
896896
return;
897897

898+
iscsi_session_remove(cls_session);
899+
/*
900+
* Our get_host_param needs to access the session, so remove the
901+
* host from sysfs before freeing the session to make sure userspace
902+
* is no longer accessing the callout.
903+
*/
904+
iscsi_host_remove(shost);
905+
898906
iscsi_tcp_r2tpool_free(cls_session->dd_data);
899-
iscsi_session_teardown(cls_session);
900907

901-
iscsi_host_remove(shost);
908+
iscsi_session_free(cls_session);
902909
iscsi_host_free(shost);
903910
}
904911

‎drivers/scsi/libiscsi.c

Lines changed: 31 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -2836,17 +2836,32 @@ iscsi_session_setup(struct iscsi_transport *iscsit, struct Scsi_Host *shost,
28362836
}
28372837
EXPORT_SYMBOL_GPL(iscsi_session_setup);
28382838

2839-
/**
2840-
* iscsi_session_teardown - destroy session, host, and cls_session
2841-
* @cls_session: iscsi session
2839+
/*
2840+
* issi_session_remove - Remove session from iSCSI class.
28422841
*/
2843-
void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
2842+
void iscsi_session_remove(struct iscsi_cls_session *cls_session)
28442843
{
28452844
struct iscsi_session *session = cls_session->dd_data;
2846-
struct module *owner = cls_session->transport->owner;
28472845
struct Scsi_Host *shost = session->host;
28482846

28492847
iscsi_remove_session(cls_session);
2848+
/*
2849+
* host removal only has to wait for its children to be removed from
2850+
* sysfs, and iscsi_tcp needs to do iscsi_host_remove before freeing
2851+
* the session, so drop the session count here.
2852+
*/
2853+
iscsi_host_dec_session_cnt(shost);
2854+
}
2855+
EXPORT_SYMBOL_GPL(iscsi_session_remove);
2856+
2857+
/**
2858+
* iscsi_session_free - Free iscsi session and it's resources
2859+
* @cls_session: iscsi session
2860+
*/
2861+
void iscsi_session_free(struct iscsi_cls_session *cls_session)
2862+
{
2863+
struct iscsi_session *session = cls_session->dd_data;
2864+
struct module *owner = cls_session->transport->owner;
28502865

28512866
iscsi_pool_free(&session->cmdpool);
28522867
kfree(session->password);
@@ -2864,10 +2879,19 @@ void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
28642879
kfree(session->discovery_parent_type);
28652880

28662881
iscsi_free_session(cls_session);
2867-
2868-
iscsi_host_dec_session_cnt(shost);
28692882
module_put(owner);
28702883
}
2884+
EXPORT_SYMBOL_GPL(iscsi_session_free);
2885+
2886+
/**
2887+
* iscsi_session_teardown - destroy session and cls_session
2888+
* @cls_session: iscsi session
2889+
*/
2890+
void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
2891+
{
2892+
iscsi_session_remove(cls_session);
2893+
iscsi_session_free(cls_session);
2894+
}
28712895
EXPORT_SYMBOL_GPL(iscsi_session_teardown);
28722896

28732897
/**

‎include/scsi/libiscsi.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -401,6 +401,8 @@ extern int iscsi_target_alloc(struct scsi_target *starget);
401401
extern struct iscsi_cls_session *
402402
iscsi_session_setup(struct iscsi_transport *, struct Scsi_Host *shost,
403403
uint16_t, int, int, uint32_t, unsigned int);
404+
void iscsi_session_remove(struct iscsi_cls_session *cls_session);
405+
void iscsi_session_free(struct iscsi_cls_session *cls_session);
404406
extern void iscsi_session_teardown(struct iscsi_cls_session *);
405407
extern void iscsi_session_recovery_timedout(struct iscsi_cls_session *);
406408
extern int iscsi_set_param(struct iscsi_cls_conn *cls_conn,

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