CVE-2025-68285

In the Linux kernel, the following vulnerability has been resolved:

libceph: fix potential use-after-free in havemonandosdmap()

The wait loop in _cephopensession() can race with the client receiving a new monmap or osdmap shortly after the initial map is received. Both cephmonchandlemap() and handleonemap() install a new map immediately after freeing the old one

kfree(monc->monmap);
monc->monmap = monmap;

ceph_osdmap_destroy(osdc->osdmap);
osdc->osdmap = newmap;

under client->monc.mutex and client->osdc.lock respectively, but because neither is taken in havemonandosdmap() it's possible for client->monc.monmap->epoch and client->osdc.osdmap->epoch arms in

client->monc.monmap && client->monc.monmap->epoch &&
    client->osdc.osdmap && client->osdc.osdmap->epoch;

condition to dereference an already freed map. This happens to be reproducible with generic/395 and generic/397 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
...
Call Trace:
<TASK>
have_mon_and_osd_map+0x56/0x70
ceph_open_session+0x182/0x290
ceph_get_tree+0x333/0x680
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
</TASK>

Allocated by task 13305:
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:
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

Rewrite the wait loop to check the above condition directly with client->monc.mutex and client->osdc.lock taken as appropriate. While at it, improve the timeout handling (previously mounttimeout could be exceeded in case waiteventinterruptibletimeout() slept more than once) and access client->autherr under client->monc.mutex to match how it's set in finishauth().

monmapshow() and osdmapshow() now take the respective lock before accessing the map as well.