On Wed, 2025-06-11 at 13:22 +0200, Ilya Dryomov wrote:
> On Tue, Apr 15, 2025 at 12:10 AM Viacheslav Dubeyko
> <slava@xxxxxxxxxxx> wrote:
> >
> > From: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>
> >
> > The generic/395 and generic/397 is capable of generating
> > the oops is on line net/ceph/ceph_common.c:794 with
> > KASAN enabled.
> >
> > BUG: KASAN: slab-use-after-free in have_mon_and_osd_map+0x56/0x70
> > Read of size 4 at addr ffff88811012d810 by task mount.ceph/13305
> >
> > CPU: 2 UID: 0 PID: 13305 Comm: mount.ceph Not tainted 6.14.0-rc2-
> > build2+ #1266
> > Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0x57/0x80
> > ? have_mon_and_osd_map+0x56/0x70
> > print_address_description.constprop.0+0x84/0x330
> > ? have_mon_and_osd_map+0x56/0x70
> > print_report+0xe2/0x1e0
> > ? rcu_read_unlock_sched+0x60/0x80
> > ? kmem_cache_debug_flags+0xc/0x20
> > ? fixup_red_left+0x17/0x30
> > ? have_mon_and_osd_map+0x56/0x70
> > kasan_report+0x8d/0xc0
> > ? have_mon_and_osd_map+0x56/0x70
> > have_mon_and_osd_map+0x56/0x70
> > ceph_open_session+0x182/0x290
> > ? __pfx_ceph_open_session+0x10/0x10
> > ? __init_swait_queue_head+0x8d/0xa0
> > ? __pfx_autoremove_wake_function+0x10/0x10
> > ? shrinker_register+0xdd/0xf0
> > ceph_get_tree+0x333/0x680
> > vfs_get_tree+0x49/0x180
> > do_new_mount+0x1a3/0x2d0
> > ? __pfx_do_new_mount+0x10/0x10
> > ? security_capable+0x39/0x70
> > path_mount+0x6dd/0x730
> > ? __pfx_path_mount+0x10/0x10
> > ? kmem_cache_free+0x1e5/0x270
> > ? user_path_at+0x48/0x60
> > do_mount+0x99/0xe0
> > ? __pfx_do_mount+0x10/0x10
> > ? lock_release+0x155/0x190
> > __do_sys_mount+0x141/0x180
> > do_syscall_64+0x9f/0x100
> > entry_SYSCALL_64_after_hwframe+0x76/0x7e
> > RIP: 0033:0x7f01b1b14f3e
> > Code: 48 8b 0d d5 3e 0f 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f
> > 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 a5 00 00 00 0f 05
> > <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a2 3e 0f 00 f7 d8 64 89 01 48
> > RSP: 002b:00007fffd129fa08 EFLAGS: 00000246 ORIG_RAX:
> > 00000000000000a5
> > RAX: ffffffffffffffda RBX: 0000564ec01a7850 RCX: 00007f01b1b14f3e
> > RDX: 0000564ec00f2225 RSI: 00007fffd12a1964 RDI: 0000564ec0147a20
> > RBP: 00007fffd129fbd0 R08: 0000564ec014da90 R09: 0000000000000080
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007fffd12a194e
> > R13: 0000000000000000 R14: 00007fffd129fa50 R15: 00007fffd129fa40
> > </TASK>
> >
> > Allocated by task 13305:
> > stack_trace_save+0x8c/0xc0
> > kasan_save_stack+0x1e/0x40
> > kasan_save_track+0x10/0x30
> > __kasan_kmalloc+0x3a/0x50
> > __kmalloc_noprof+0x247/0x290
> > ceph_osdmap_alloc+0x16/0x130
> > ceph_osdc_init+0x27a/0x4c0
> > ceph_create_client+0x153/0x190
> > create_fs_client+0x50/0x2a0
> > ceph_get_tree+0xff/0x680
> > vfs_get_tree+0x49/0x180
> > do_new_mount+0x1a3/0x2d0
> > path_mount+0x6dd/0x730
> > do_mount+0x99/0xe0
> > __do_sys_mount+0x141/0x180
> > do_syscall_64+0x9f/0x100
> > entry_SYSCALL_64_after_hwframe+0x76/0x7e
> >
> > Freed by task 9475:
> > stack_trace_save+0x8c/0xc0
> > kasan_save_stack+0x1e/0x40
> > kasan_save_track+0x10/0x30
> > kasan_save_free_info+0x3b/0x50
> > __kasan_slab_free+0x18/0x30
> > kfree+0x212/0x290
> > handle_one_map+0x23c/0x3b0
> > ceph_osdc_handle_map+0x3c9/0x590
> > mon_dispatch+0x655/0x6f0
> > ceph_con_process_message+0xc3/0xe0
> > ceph_con_v1_try_read+0x614/0x760
> > ceph_con_workfn+0x2de/0x650
> > process_one_work+0x486/0x7c0
> > process_scheduled_works+0x73/0x90
> > worker_thread+0x1c8/0x2a0
> > kthread+0x2ec/0x300
> > ret_from_fork+0x24/0x40
> > ret_from_fork_asm+0x1a/0x30
> >
> > The buggy address belongs to the object at ffff88811012d800
> > which belongs to the cache kmalloc-512 of size 512
> > The buggy address is located 16 bytes inside of
> > freed 512-byte region [ffff88811012d800, ffff88811012da00)
> >
> > The buggy address belongs to the physical page:
> > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
> > pfn:0x11012c
> > head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0
> > pincount:0
> > flags: 0x200000000000040(head|node=0|zone=2)
> > page_type: f5(slab)
> > raw: 0200000000000040 ffff888100042c80 dead000000000100
> > dead000000000122
> > raw: 0000000000000000 0000000080100010 00000000f5000000
> > 0000000000000000
> > head: 0200000000000040 ffff888100042c80 dead000000000100
> > dead000000000122
> > head: 0000000000000000 0000000080100010 00000000f5000000
> > 0000000000000000
> > head: 0200000000000002 ffffea0004404b01 ffffffffffffffff
> > 0000000000000000
> > head: 0000000000000004 0000000000000000 00000000ffffffff
> > 0000000000000000
> > page dumped because: kasan: bad access detected
> >
> > Memory state around the buggy address:
> > ffff88811012d700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff88811012d780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >
> > ffff88811012d800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > fb
> >
> > ^
> > ffff88811012d880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff88811012d900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ==================================================================
> > Disabling lock debugging due to kernel taint
> > libceph: client274326 fsid 8598140e-35c2-11ee-b97c-001517c545cc
> > libceph: mon0 (1)90.155.74.19:6789 session established
> > libceph: client274327 fsid 8598140e-35c2-11ee-b97c-001517c545cc
> >
> > We have such scenario:
> >
> > Thread 1:
> > void ceph_osdmap_destroy(...) {
> > <skipped>
> > kfree(map);
> > }
> > Thread 1 sleep...
> >
> > Thread 2:
> > static bool have_mon_and_osd_map(struct ceph_client *client) {
> > return client->monc.monmap && client->monc.monmap->epoch &&
> > client->osdc.osdmap && client->osdc.osdmap->epoch;
> > }
> > Thread 2 has oops...
> >
> > Thread 1 wake up:
> > static int handle_one_map(...) {
> > <skipped>
> > osdc->osdmap = newmap;
> > <skipped>
> > }
> >
> > This patch introduces a have_mon_and_osd_map atomic_t
> > field in struct ceph_client. If there is no OSD and
> > monitor maps, then the client->have_mon_and_osd_map
> > is equal to zero. The OSD and monitor maps initialization
> > results in incrementing of client->have_mon_and_osd_map
> > under the lock. As a result, have_mon_and_osd_map() function
> > simply checks now that client->have_mon_and_osd_map is equal to
> > CEPH_CLIENT_HAS_MON_AND_OSD_MAP.
> >
> > Patch adds locking in the ceph_osdc_stop()
> > method during the destructruction of osdc->osdmap and
> > assigning of NULL to the pointer. The lock is used
> > in the ceph_monc_stop() during the freeing of monc->monmap
> > and assigning NULL to the pointer too. The monmap_show()
> > and osdmap_show() methods were reworked to prevent
> > the potential race condition during the methods call.
> >
> > Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>
> > ---
> > include/linux/ceph/libceph.h | 20 ++++++++++++++++++++
> > net/ceph/ceph_common.c | 6 ++++--
> > net/ceph/debugfs.c | 17 +++++++++++++----
> > net/ceph/mon_client.c | 18 +++++++++++++++++-
> > net/ceph/osd_client.c | 11 +++++++++++
> > 5 files changed, 65 insertions(+), 7 deletions(-)
> >
> > diff --git a/include/linux/ceph/libceph.h
> > b/include/linux/ceph/libceph.h
> > index 733e7f93db66..f5694bf5bd54 100644
> > --- a/include/linux/ceph/libceph.h
> > +++ b/include/linux/ceph/libceph.h
> > @@ -132,6 +132,7 @@ struct ceph_client {
> > struct ceph_messenger msgr; /* messenger instance */
> > struct ceph_mon_client monc;
> > struct ceph_osd_client osdc;
> > + atomic_t have_mon_and_osd_map;
> >
> > #ifdef CONFIG_DEBUG_FS
> > struct dentry *debugfs_dir;
> > @@ -141,6 +142,25 @@ struct ceph_client {
> > #endif
> > };
> >
> > +/*
> > + * The have_mon_and_osd_map possible states
> > + */
> > +enum {
> > + CEPH_CLIENT_HAS_NO_MON_AND_NO_OSD_MAP = 0,
> > + CEPH_CLIENT_HAS_ONLY_ONE_MAP = 1,
> > + CEPH_CLIENT_HAS_MON_AND_OSD_MAP = 2,
> > + CEPH_CLIENT_MAP_STATE_UNKNOWN
> > +};
> > +
> > +static inline
> > +bool is_mon_and_osd_map_state_invalid(struct ceph_client *client)
> > +{
> > + int have_mon_and_osd_map = atomic_read(&client-
> > >have_mon_and_osd_map);
> > +
> > + return have_mon_and_osd_map <
> > CEPH_CLIENT_HAS_NO_MON_AND_NO_OSD_MAP ||
> > + have_mon_and_osd_map >=
> > CEPH_CLIENT_MAP_STATE_UNKNOWN;
> > +}
> > +
> > #define from_msgr(ms) container_of(ms, struct ceph_client, msgr)
> >
> > static inline bool ceph_msgr2(struct ceph_client *client)
> > diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
> > index 4c6441536d55..62efceb3b19d 100644
> > --- a/net/ceph/ceph_common.c
> > +++ b/net/ceph/ceph_common.c
> > @@ -723,6 +723,8 @@ struct ceph_client *ceph_create_client(struct
> > ceph_options *opt, void *private)
> >
> > mutex_init(&client->mount_mutex);
> > init_waitqueue_head(&client->auth_wq);
> > + atomic_set(&client->have_mon_and_osd_map,
> > + CEPH_CLIENT_HAS_NO_MON_AND_NO_OSD_MAP);
> > client->auth_err = 0;
> >
> > client->extra_mon_dispatch = NULL;
> > @@ -790,8 +792,8 @@ EXPORT_SYMBOL(ceph_reset_client_addr);
> > */
> > static bool have_mon_and_osd_map(struct ceph_client *client)
> > {
> > - return client->monc.monmap && client->monc.monmap->epoch &&
> > - client->osdc.osdmap && client->osdc.osdmap->epoch;
> > + return atomic_read(&client->have_mon_and_osd_map) ==
> > + CEPH_CLIENT_HAS_MON_AND_OSD_MAP;
> > }
> >
> > /*
> > diff --git a/net/ceph/debugfs.c b/net/ceph/debugfs.c
> > index 2110439f8a24..7b45c169a859 100644
> > --- a/net/ceph/debugfs.c
> > +++ b/net/ceph/debugfs.c
> > @@ -36,8 +36,10 @@ static int monmap_show(struct seq_file *s, void
> > *p)
> > int i;
> > struct ceph_client *client = s->private;
> >
> > + mutex_lock(&client->monc.mutex);
> > +
> > if (client->monc.monmap == NULL)
> > - return 0;
> > + goto out_unlock;
> >
> > seq_printf(s, "epoch %d\n", client->monc.monmap->epoch);
> > for (i = 0; i < client->monc.monmap->num_mon; i++) {
> > @@ -48,6 +50,10 @@ static int monmap_show(struct seq_file *s, void
> > *p)
> > ENTITY_NAME(inst->name),
> > ceph_pr_addr(&inst->addr));
> > }
> > +
> > +out_unlock:
> > + mutex_unlock(&client->monc.mutex);
> > +
> > return 0;
> > }
> >
> > @@ -56,13 +62,15 @@ static int osdmap_show(struct seq_file *s, void
> > *p)
> > int i;
> > struct ceph_client *client = s->private;
> > struct ceph_osd_client *osdc = &client->osdc;
> > - struct ceph_osdmap *map = osdc->osdmap;
> > + struct ceph_osdmap *map = NULL;
> > struct rb_node *n;
> >
> > + down_read(&osdc->lock);
> > +
> > + map = osdc->osdmap;
> > if (map == NULL)
> > - return 0;
> > + goto out_unlock;
> >
> > - down_read(&osdc->lock);
> > seq_printf(s, "epoch %u barrier %u flags 0x%x\n", map-
> > >epoch,
> > osdc->epoch_barrier, map->flags);
> >
> > @@ -131,6 +139,7 @@ static int osdmap_show(struct seq_file *s, void
> > *p)
> > seq_printf(s, "]\n");
> > }
> >
> > +out_unlock:
> > up_read(&osdc->lock);
> > return 0;
> > }
> > diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
> > index ab66b599ac47..5cf802236426 100644
> > --- a/net/ceph/mon_client.c
> > +++ b/net/ceph/mon_client.c
> > @@ -562,12 +562,16 @@ static void ceph_monc_handle_map(struct
> > ceph_mon_client *monc,
> > goto out;
> > }
> >
> > + atomic_dec(&client->have_mon_and_osd_map);
> > +
> > kfree(monc->monmap);
> > monc->monmap = monmap;
> >
> > __ceph_monc_got_map(monc, CEPH_SUB_MONMAP, monc->monmap-
> > >epoch);
> > client->have_fsid = true;
> >
> > + atomic_inc(&client->have_mon_and_osd_map);
> > +
> > out:
> > mutex_unlock(&monc->mutex);
> > wake_up_all(&client->auth_wq);
> > @@ -1220,6 +1224,9 @@ int ceph_monc_init(struct ceph_mon_client
> > *monc, struct ceph_client *cl)
> >
> > monc->fs_cluster_id = CEPH_FS_CLUSTER_ID_NONE;
> >
> > + atomic_inc(&monc->client->have_mon_and_osd_map);
>
> Hi Slava,
>
> Incrementing client->have_mon_and_osd_map here and in
> ceph_osdc_init()
> means that counter would be set to 2
> (CEPH_CLIENT_HAS_MON_AND_OSD_MAP)
> at the initialization time, way before a session with the monitor is
> established and any map is received. This effectively disables the
> wait logic in __ceph_open_session() because of have_mon_and_osd_map()
> immediately returning true. __ceph_open_session() is responsible for
> setting up the debugfs directory and that is affected too: it's
> created
> as 00000000-0000-0000-0000-000000000000.client0 because neither the
> cluster FSID nor the client ID is known without the monmap.
>
> This patch seems to be over-complicated for what it needs to do:
> I don't see a compelling reason for introducing the atomic and as
> mentioned before there is no need to attempt to guard against someone
> continuing to use the client after ceph_osdc_stop() and
> ceph_monc_stop()
> are called. It's the point of no return and the client itself gets
> freed very shortly after.
>
> Why not just open-code the wait loop in __ceph_open_session() to
> allow
> for monc->mutex and osdc->lock (for read) to be taken freely? It
> should
> be a small change in __ceph_open_session() -- net/ceph/mon_client.c
> and
> net/ceph/osd_client.c wouldn't need to be touched at all.
>
Hi Ilya,
Frankly speaking, I don't quite follow to your point. The main issue
happens when one thread calls ceph_osdc_handle_map() [1] ->
handle_one_map() [2]:
ceph_osdmap_destroy() [3] -> kfree(map) -> go to sleep
<-- another thread receives time slices to execute:
have_mon_and_osd_map() BUT osdc->osdmap is already freed and invalid
here!!!
osdc->osdmap = newmap;
So, it's not about ceph_osdc_stop() or ceph_monc_stop() but it's about
regular operations.
I've tried to exclude the necessity to use locks at all in
have_mon_and_osd_map(). Do you mean that wait loop will be better
solution? It sounds pretty complicated too for my taste and it will
require coordination among threads. No? I am not completely sure that I
follow to your vision.
Thanks,
Slava.
[1]
https://elixir.bootlin.com/linux/v6.15/source/net/ceph/osd_client.c#L4130
[2]
https://elixir.bootlin.com/linux/v6.15/source/net/ceph/osd_client.c#L4048
[3]
https://elixir.bootlin.com/linux/v6.15/source/net/ceph/osdmap.c#L1143
> Thanks,
>
> Ilya
>
> > + WARN_ON(is_mon_and_osd_map_state_invalid(monc->client));
> > +
> > return 0;
> >
> > out_auth_reply:
> > @@ -1232,6 +1239,7 @@ int ceph_monc_init(struct ceph_mon_client
> > *monc, struct ceph_client *cl)
> > ceph_auth_destroy(monc->auth);
> > out_monmap:
> > kfree(monc->monmap);
> > + monc->monmap = NULL;
> > out:
> > return err;
> > }
> > @@ -1239,6 +1247,8 @@ EXPORT_SYMBOL(ceph_monc_init);
> >
> > void ceph_monc_stop(struct ceph_mon_client *monc)
> > {
> > + struct ceph_monmap *old_monmap;
> > +
> > dout("stop\n");
> >
> > mutex_lock(&monc->mutex);
> > @@ -1266,7 +1276,13 @@ void ceph_monc_stop(struct ceph_mon_client
> > *monc)
> > ceph_msg_put(monc->m_subscribe);
> > ceph_msg_put(monc->m_subscribe_ack);
> >
> > - kfree(monc->monmap);
> > + mutex_lock(&monc->mutex);
> > + WARN_ON(is_mon_and_osd_map_state_invalid(monc->client));
> > + atomic_dec(&monc->client->have_mon_and_osd_map);
> > + old_monmap = monc->monmap;
> > + monc->monmap = NULL;
> > + mutex_unlock(&monc->mutex);
> > + kfree(old_monmap);
> > }
> > EXPORT_SYMBOL(ceph_monc_stop);
> >
> > diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> > index b24afec24138..14a91603bf6d 100644
> > --- a/net/ceph/osd_client.c
> > +++ b/net/ceph/osd_client.c
> > @@ -4068,8 +4068,10 @@ static int handle_one_map(struct
> > ceph_osd_client *osdc,
> > skipped_map = true;
> > }
> >
> > + atomic_dec(&osdc->client->have_mon_and_osd_map);
> > ceph_osdmap_destroy(osdc->osdmap);
> > osdc->osdmap = newmap;
> > + atomic_inc(&osdc->client->have_mon_and_osd_map);
> > }
> >
> > was_full &= !ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL);
> > @@ -5266,6 +5268,9 @@ int ceph_osdc_init(struct ceph_osd_client
> > *osdc, struct ceph_client *client)
> > schedule_delayed_work(&osdc->osds_timeout_work,
> > round_jiffies_relative(osdc->client->options-
> > >osd_idle_ttl));
> >
> > + atomic_inc(&osdc->client->have_mon_and_osd_map);
> > + WARN_ON(is_mon_and_osd_map_state_invalid(osdc->client));
> > +
> > return 0;
> >
> > out_notify_wq:
> > @@ -5278,6 +5283,7 @@ int ceph_osdc_init(struct ceph_osd_client
> > *osdc, struct ceph_client *client)
> > mempool_destroy(osdc->req_mempool);
> > out_map:
> > ceph_osdmap_destroy(osdc->osdmap);
> > + osdc->osdmap = NULL;
> > out:
> > return err;
> > }
> > @@ -5306,10 +5312,15 @@ void ceph_osdc_stop(struct ceph_osd_client
> > *osdc)
> > WARN_ON(atomic_read(&osdc->num_requests));
> > WARN_ON(atomic_read(&osdc->num_homeless));
> >
> > + down_write(&osdc->lock);
> > + WARN_ON(is_mon_and_osd_map_state_invalid(osdc->client));
> > + atomic_dec(&osdc->client->have_mon_and_osd_map);
> > ceph_osdmap_destroy(osdc->osdmap);
> > + osdc->osdmap = NULL;
> > mempool_destroy(osdc->req_mempool);
> > ceph_msgpool_destroy(&osdc->msgpool_op);
> > ceph_msgpool_destroy(&osdc->msgpool_op_reply);
> > + up_write(&osdc->lock);
> > }
> >
> > int osd_req_op_copy_from_init(struct ceph_osd_request *req,
> > --
> > 2.48.0
> >
