On Tue, 2025-07-01 at 21:57 +0200, Ilya Dryomov wrote:
> On Wed, Jun 18, 2025 at 9:16 PM 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 fixes the issue by means of locking
> > client->osdc.lock and client->monc.mutex before
> > the checking client->osdc.osdmap and
> > client->monc.monmap in have_mon_and_osd_map() function.
> > 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.
> >
> > Reported-by: David Howells <dhowells@xxxxxxxxxx>
> > Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>
> > ---
> > net/ceph/ceph_common.c | 34 +++++++++++++++++++++++++++++-----
> > net/ceph/debugfs.c | 17 +++++++++++++----
> > net/ceph/mon_client.c | 9 ++++++++-
> > net/ceph/osd_client.c | 4 ++++
> > 4 files changed, 54 insertions(+), 10 deletions(-)
> >
> > diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
> > index 4c6441536d55..a28b29c763ca 100644
> > --- a/net/ceph/ceph_common.c
> > +++ b/net/ceph/ceph_common.c
> > @@ -790,8 +790,18 @@ 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;
> > + bool have_mon_map = false;
> > + bool have_osd_map = false;
> > +
> > + mutex_lock(&client->monc.mutex);
> > + have_mon_map = client->monc.monmap && client->monc.monmap-
> > >epoch;
> > + mutex_unlock(&client->monc.mutex);
> > +
> > + down_read(&client->osdc.lock);
> > + have_osd_map = client->osdc.osdmap && client->osdc.osdmap-
> > >epoch;
> > + up_read(&client->osdc.lock);
> > +
> > + return have_mon_map && have_osd_map;
> > }
> >
> > /*
> > @@ -813,9 +823,23 @@ int __ceph_open_session(struct ceph_client
> > *client, unsigned long started)
> >
> > /* wait */
> > dout("mount waiting for mon_map\n");
> > - err = wait_event_interruptible_timeout(client-
> > >auth_wq,
> > - have_mon_and_osd_map(client) || (client-
> > >auth_err < 0),
> > - ceph_timeout_jiffies(timeout));
> > +
> > + DEFINE_WAIT_FUNC(wait, woken_wake_function);
> > +
> > + add_wait_queue(&client->auth_wq, &wait);
> > +
> > + while (!(have_mon_and_osd_map(client) ||
> > + (client->auth_err < 0))) {
>
> Hi Slava,
>
> This looks much better but misses two points raised in the comments
> on
> previous versions. The first point is that it would be better to
> access client->auth_err under client->monc.mutex, matching how it's
> set
> in finish_auth() -- now that locks can be freely taken here it should
> be a trivial change.
>
OK. Let me rework the patch. I hope it will be trivial change. :)
> > + if (signal_pending(current)) {
> > + err = -ERESTARTSYS;
> > + break;
> > + }
> > + wait_woken(&wait, TASK_INTERRUPTIBLE,
> > + ceph_timeout_jiffies(timeout));
> > + }
> > +
> > + remove_wait_queue(&client->auth_wq, &wait);
> > +
> > if (err < 0)
> > return err;
> > if (client->auth_err < 0)
>
> Separately, I wonder if the new nested loop which checks both for the
> presence of maps and client->auth_err could be merged into the
> existing
> outer loop which currently checks for the presence of maps in the
> loop
> condition and client->auth_err here in the loop body. Having a
> single
> loop with everything checked in just one place would be a lot
> cleaner.
>
Let me take a deeper look into the code. I hope I follow your point.
> > 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..b299e5bbddb1 100644
> > --- a/net/ceph/mon_client.c
> > +++ b/net/ceph/mon_client.c
> > @@ -1232,6 +1232,7 @@ 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 +1240,8 @@ 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 +1269,11 @@ 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);
> > + old_monmap = monc->monmap;
> > + monc->monmap = NULL;
> > + mutex_unlock(&monc->mutex);
> > + kfree(old_monmap);
>
> The second point is that locking (or any changes at all) in
> ceph_monc_stop() and ceph_osdc_stop() shouldn't be needed. As
> mentioned before, it's the point of no return where the entire client
> including monc and osdc parts gets freed very shortly after.
>
I see. You still dislike this locking logic here. :) OK. I can rework
it too.
Thanks,
Slava.
