diff options
| author | Yogesh Gaur <yogeshgaur.83@gmail.com> | 2026-09-11 19:01:09 +0530 |
|---|---|---|
| committer | Ilya Dryomov <idryomov@gmail.com> | 2026-10-26 14:15:47 +0100 |
| commit | 94dbce2ae4fdb57bdb53ffa3456da777a5cfb981 (patch) | |
| tree | b37e7fd694ebeea4312540e08ce260efa141c57b /net | |
| parent | d8fc89b5bfe4cb3aebe4c8a818247d11291b841c (diff) | |
libceph: reject an initial monmap with no monitors
build_initial_monmap() takes the monitor count straight from
ceph_options::num_mon and builds a monmap with that many entries without
checking that there is at least one. ceph_parse_ips() writes *count only
after it has parsed an address successfully, so a ceph_options that went
through a failed parse still has num_mon == 0 and the resulting monmap
has no monitors in it at all.
The first thing the client does with that monmap is open a session, and
pick_new_mon() asserts the invariant that it is non-empty:
kernel BUG at net/ceph/mon_client.c:211!
RIP: 0010:pick_new_mon net/ceph/mon_client.c:211 [inline]
RIP: 0010:__open_session+0x60f/0x740 net/ceph/mon_client.c:245
Call Trace:
ceph_monc_open_session+0x46/0x60 net/ceph/mon_client.c:534
__ceph_open_session+0x135/0x590 net/ceph/ceph_common.c:798
ceph_real_mount fs/ceph/super.c:1173 [inline]
ceph_get_tree+0xd98/0x1fd0 fs/ceph/super.c:1362
vfs_get_tree+0x92/0x320 fs/super.c:1947
vfs_cmd_create+0xd7/0x2a0 fs/fsopen.c:231
__do_sys_fsconfig+0x55a/0xcb0 fs/fsopen.c:463
The reproducer gets there through the new device syntax: an fsconfig()
mon_addr= that does not resolve ("libceph: resolve '127.0.0.' (ret=-3):
failed") leaves fsopt->mon_addr set but num_mon at 0, so the "No monitor
address" check in ceph_get_tree() passes and the mount proceeds with an
empty monmap. The next patch stops that string from being kept, but the
assertion should not be reachable from a mount option in the first place.
Commit 40480eee361e ("libceph: Reject monmaps advertising zero monitors")
made the same BUG_ON() unreachable from the wire by rejecting
num_mon == 0 in ceph_monmap_decode(). Apply the same rule to the initial
monmap, which is the only other way one gets built, and fail the mount
with -EINVAL rather than assert afterwards.
Cc: stable@vger.kernel.org
Fixes: 7b19b4db5add ("ceph: new device mount syntax")
Reported-by: syzbot+1dbed5969931c19d3eb5@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1dbed5969931c19d3eb5
Assisted-by: Cursor
Signed-off-by: Yogesh Gaur <yogeshgaur.83@gmail.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ceph/mon_client.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c index c56457378d00..bcbcf47506c9 100644 --- a/net/ceph/mon_client.c +++ b/net/ceph/mon_client.c @@ -1141,6 +1141,9 @@ static int build_initial_monmap(struct ceph_mon_client *monc) int num_mon = opt->num_mon; int i; + if (num_mon < 1 || num_mon > CEPH_MAX_MON) + return -EINVAL; + /* build initial monmap */ monc->monmap = kzalloc_flex(*monc->monmap, mon_inst, num_mon); if (!monc->monmap) |