| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: initialize copy-notify stateid before publishing it
nfsd4_copy_notify() finished initializing the cpntf state after
nfs4_alloc_init_cpntf_state() had already linked it into the
s2s_cp_stateids IDR and the parent's sc_cp_list, with cs_count == 1 (the
membership reference) and none held for the caller. A racing
OFFLOAD_CANCEL (crafted cl_id == nn->s2s_cp_cl_id plus the guessable
so_id) could reach manage_cpntf_state() and free the entry, turning the
caller's subsequent cpn_cnr_stateid read and cp_p_stateid/cp_p_clid
writes into use-after-free. The owning clientid was also only recorded
after publication, so it could not gate an ownership check in that window.
Record cp_p_stateid and cp_p_clid inside nfs4_alloc_init_cpntf_state()
before nfs4_init_cp_state() publishes the entry, and return it with an
extra reference. The caller reads the stateid under that reference and
drops it with nfs4_put_cpntf_state(); on a late error the laundromat
reaps the entry. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: move nfsd_debugfs_init() after nfsd4_init_slabs() in init_nfsd()
nfsd_debugfs_init() runs before nfsd4_init_slabs() in init_nfsd().
If the slab allocation fails, the bare "return retval" bypasses
nfsd_debugfs_exit(), leaving orphan debugfs files with stale fops
pointers into the freed module text.
Move nfsd_debugfs_init() to after the slab init succeeds, so the
early return has no debugfs state to clean up.
Since debugfs is now the more recently initialized of the two, also
update the unwind paths to match reverse-initialization (LIFO) order:
run nfsd_debugfs_exit() before nfsd4_free_slabs() in both the
init_nfsd() error path and exit_nfsd(). The nfsd debugfs files only
reference module-global state and have no dependency on the slab
caches, so that reordering is a cleanup with no functional change. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: close shrinker/GC/fsnotify vs per-net shutdown race in filecache
The shrinker, GC worker, and fsnotify/lease callbacks can unhash an
nfsd_file from the rhashtable and then call
nfsd_file_dispose_list_delayed() to move it to the per-net dispose list.
If nfsd_file_cache_shutdown_net() runs concurrently, its rhashtable walk
misses the already-unhashed file, and its drain of the per-net dispose
list can run before the file has been queued. The file then sits on
the per-net list with no thread to drain it, leaking both the file and
its associated state.
The GC worker and shrinker already hold nfsd_gc_lock while walking the
LRU, but in the original code they release it before calling
nfsd_file_dispose_list_delayed(). The fsnotify/lease path
(nfsd_file_close_inode) has no synchronization at all.
Fix this by:
1. Widening nfsd_gc_lock in both nfsd_file_gc() and nfsd_file_lru_scan()
to cover the nfsd_file_dispose_list_delayed() call.
2. Wrapping nfsd_file_close_inode() in nfsd_gc_lock so that all three
callers of nfsd_file_dispose_list_delayed() hold the lock.
3. Adding a spin_lock/unlock(nfsd_gc_lock) barrier in
nfsd_file_cache_shutdown_net() after the purge, so that any
in-progress disposal has fully completed before the per-net list
is drained.
All operations inside the lock are non-sleeping (rhashtable lookups,
atomic bit/refcount ops, list moves, svc_wake_up), so the spinlock is
appropriate. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: reject out-of-range useconds in NFSv2 SETATTR/CREATE
The NFSv2 sattr decoder converts the wire useconds to nanoseconds in
svcxdr_decode_sattr():
iap->ia_atime.tv_nsec = tmp2 * NSEC_PER_USEC;
tmp2 is a u32 and NSEC_PER_USEC is 1000, so the product is computed in
unsigned long. On ILP32 that is 32 bits, and an out-of-range useconds
value such as 4294968 wraps to tv_nsec == 704. The corruption therefore
happens during decode, before any proc function can inspect the value,
and a later range check on tv_nsec would see an in-range result and
accept it. Rejecting in the decoder yields an RPC GARBAGE_ARGS reply.
NFSv2 defines no NFSERR_INVAL, so there is no NFS-level status to return
for a malformed time argument, and the check cannot move to the proc
function the way the v3/v4 nsec range checks do.
Guard the raw useconds before the multiplication and reject values
greater than 1000000. useconds == 1000000 is kept: it is the Sun
convention for "set to the current server time", and the in-tree Linux
NFSv2 client emits it in both the atime and the mtime field for a plain
touch / utimes(file, NULL) (see encode_sattr() and
xdr_encode_current_server_time() in fs/nfs/nfs2xdr.c). Rejecting 1000000
would turn that common operation into a hard decode failure for both
SETATTR and CREATE. 1000000 * NSEC_PER_USEC is 10^9, which does not wrap
on ILP32, so the Sun convention value passes through safely. Only
genuinely out-of-range values (> 1000000) are rejected. The atime and
mtime guards are therefore symmetric.
The decoder only applied the Sun convention in the mtime block, which
clears ATTR_ATIME_SET|ATTR_MTIME_SET when mtime useconds == 1000000. If a
client puts 1000000 in the atime field but not in the mtime field, the
atime block stored an out-of-range tv_nsec (10^9) and left ATTR_ATIME_SET
set, so the bogus value reached the filesystem. Apply the convention in
the atime block as well, clearing ATTR_ATIME_SET so the server uses its
current time and ignores the value. Only ATTR_ATIME_SET is cleared there.
The mtime block keeps its existing behavior, where 1000000 means "set
both atime and mtime to now".
[ cel: various tweaks, addenda, and clean-ups ] |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: release OPEN-decoded posix ACLs via op_release
nfsd4_decode_createhow4() calls nfsd4_decode_fattr4(), which allocates
refcounted struct posix_acl objects via posix_acl_alloc() and stores
them in open->op_pacl and open->op_dpacl. These pointers must be
released once the OPEN compound finishes.
When nfsd4_decode_open_claim4() returns a non-seqid-mutating error,
the dispatcher short-circuits before op_func runs:
nfsd4_proc_compound()
if (op->status && op->opnum == OP_OPEN)
op->status = nfsd4_open_omfg(...)
if (!seqid_mutating_err(ntohl(op->status)))
return op->status; /* nfsd4_open() never runs */
...
opdesc->op_release(&op->u) /* must still release op_pacl/op_dpacl */
Before this change OP_OPEN had no .op_release in nfsd4_ops[], and the
release pair lived inside nfsd4_open() at its out_err: label. On the
short-circuit path nfsd4_open() is never invoked, so both posix_acl
refs leak on every malformed OPEN compound that carries valid POSIX
ACL createhow4 attributes.
Add nfsd4_open_release() and wire it as .op_release for OP_OPEN.
posix_acl_release() is NULL-safe, so the single release site covers
both the normal path and the nfsd4_open_omfg short-circuit. Remove
the matching posix_acl_release() pair from nfsd4_open()'s out_err:
label to avoid double-releasing.
The compound loop has two encoding branches: nfsd4_encode_operation()
for normal ops, and nfsd4_encode_replay() for v4.0 replayed ops.
op_release was only called from nfsd4_encode_operation(), so resources
attached to op->u leak on the replay path.
Move the op_release() call out of nfsd4_encode_operation() and the
replay branch, placing it after the if-else in nfsd4_proc_compound().
This gives a single call site in a fairly obviously-correct place,
covering both the normal encoding and replay paths. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: revoke copy-notify stateids before dropping their reference
Copy-notify stateids live in the s2s_cp_stateids IDR and on their parent
stid's sc_cp_list, pinned by a single membership reference.
_free_cpntf_state_locked() only unlinks an entry once its refcount reaches
zero, so any revoke path that runs while a concurrent
find_cpntf_state()/manage_cpntf_state() holder has elevated cs_count drops
the reference without unlinking, leaving the entry discoverable with its
membership reference already consumed. A second revoke or a laundromat tick
then frees it while the reader still holds the pointer -- a
KASAN-detectable use-after-free at the reader's nfs4_put_cpntf_state().
This affected all three revoke paths:
- The parent-stid drain (nfs4_free_cpntf_statelist()) repeatedly called
_free_cpntf_state_locked() on the first list entry; a holder that had
bumped cs_count made it return early, so the next iteration
re-decremented and burned the holder's reference.
- OFFLOAD_CANCEL (manage_cpntf_state()) and laundromat expiry likewise
used _free_cpntf_state_locked() and could drop 2->1 without unlinking.
Add revoke_cpntf_state_locked(), which unhashes the entry from the IDR and
sc_cp_list first (deferring the final free to any holder), and use it from
all three revoke paths. The drain now walks with list_for_each_entry_safe()
and revokes each entry unconditionally, so it terminates in one pass per
entry regardless of cs_count. The unhash is gated on
!list_empty(&cps->cp_list); the idr_remove() gate matters because
idr_alloc_cyclic() may have recycled the so_id by then. Keep
_free_cpntf_state_locked() for the reference-holder put path only, where a
concurrent revoke may already have unlinked the entry (its list_del_init()
then a no-op). |
| In the Linux kernel, the following vulnerability has been resolved:
NFSD: Prevent lock owner use-after-free during client teardown
__destroy_client() releases a client's open owners, but a lock owner
whose only reference is a blocked lock (nbl) stays on
cl_ownerstr_hashtbl. client_has_state() does not count a bare owner,
so DESTROY_CLIENTID can reach __destroy_client() with such owners
present.
__destroy_client() then walks the table, calling remove_blocked_locks()
on each owner without a reference. Freeing a blocked lock drops the
owner reference held via flc_owner. The per-net laundromat reaps
blocked locks from nn->blocked_locks_lru independently of client state.
The two paths share blocked_locks_lock only for the list splice, not
the owner's lifetime. The laundromat therefore frees the owner as
__destroy_client() dereferences it, a NULL dereference in
remove_blocked_locks().
nfsd4_release_lockowner() holds a reference across the same call;
__destroy_client() does not. Hold cl_lock across the walk, taking a
reference and unhashing each owner, then drop it before
remove_blocked_locks() and nfs4_put_stateowner(), which take
blocked_locks_lock and cl_lock. |
| In the Linux kernel, the following vulnerability has been resolved:
NFSD: Prevent client use-after-free during admin state revocation
A stateid holds only a bare pointer to its nfs4_client; a stateid
reference does not pin it. The client survives only because
__destroy_client() drains its stateids before free_client() runs.
nfsd4_revoke_states() drops nn->client_lock across revoke_one_stid(),
which dereferences the client to revoke a stateid and read
clp->cl_minorversion. A teardown racing the dropped lock can free
the client first.
Pinning cl_rpc_users under client_lock blocks the DESTROY_CLIENTID and
EXCHANGE_ID teardown, which refuses while cl_rpc_users is non-zero.
force_expire_client() ignores it: once its wait for cl_rpc_users to
reach zero has passed, a later pin goes unnoticed.
Under client_lock, skip a client whose cl_time is already zero --
force_expire_client() clears it there before waiting -- otherwise pin
cl_rpc_users before dropping the lock. The walk then either sees the
expiry and skips, or pins in time for that wait to cover the revoke. |
| In the Linux kernel, the following vulnerability has been resolved:
NFSD: Prevent client use-after-free during delegation revoke
A delegation stateid holds only a bare pointer to its owning
nfs4_client and does not keep it alive. The client survives its
stateids only because __destroy_client() drains cl_delegations and
cl_revoked before free_client() runs.
nfs4_laundromat() breaks that invariant: it unhashes an
expired delegation from cl_delegations, drops deleg_lock, then
revoke_delegation() relinks it onto cl_revoked under cl_lock. In that
window the delegation is on neither list, so client_has_state() can
report no remaining state.
Every teardown path first requires cl_rpc_users to be zero, but
the laundromat holds no such reference. A client whose recalled
delegation has just timed out can therefore reach free_client()
while revoke_delegation() is still about to dereference cl_lock,
a use-after-free.
Pin the client with cl_rpc_users across the revoke so teardown blocks
until it completes, then reap the delegation from cl_revoked. A client
already expiring reaps its own, so skip it and leave the delegation on
del_recall_lru. |
| In the Linux kernel, the following vulnerability has been resolved:
NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
nfs40_clean_admin_revoked() takes a stateid reference under
clp->cl_lock, drops nn->client_lock, and calls
nfsd4_drop_revoked_stid(), which dereferences the stateid's client
through s->sc_client->cl_lock. The stateid reference does not pin the
client, so a teardown racing the dropped lock can free the client
while nfsd4_drop_revoked_stid() is still using it.
This cleanup runs from the laundromat, so a periodic sweep can race
force_expire_client() driven by a write to the clients/<id>/ctl file.
Skip a client that is already expiring and otherwise pin it with
cl_rpc_users under client_lock before dropping the lock, matching
nfsd4_revoke_states(). |
| In the Linux kernel, the following vulnerability has been resolved:
libceph: validate OSD extent maps before cursor advance
net/ceph/osd_client.c:osd_sparse_read() validates that the sparse-read
data length matches the summed extent lengths, but it does not validate
that each OSD-supplied extent is monotonic and lies inside the original
request range. A malformed authenticated OSD reply can advertise a
far-forward nonzero extent offset with a matching data length and make
the client advance the message-data cursor beyond the request buffer.
This reaches the BUG_ON(!*length) assertion in ceph_msg_data_next() from
the client receive path.
Impact: A malicious or compromised authenticated Ceph OSD peer can crash
a kernel Ceph client via a malformed sparse-read reply.
Reject sparse extent maps that overflow, move backwards, overlap, or
extend outside the original sparse-read request before advancing the
cursor.
[ idryomov: perform sparse_extent_map_valid() check a bit earlier,
in CEPH_SPARSE_READ_DATA_LEN instead of CEPH_SPARSE_READ_DATA_PRE
state ] |
| In the Linux kernel, the following vulnerability has been resolved:
libceph: reject buckets with mismatched CRUSH ids
crush_decode() stores bucket data by array slot, and the mapper later
derives the per-bucket workspace index from the decoded bucket id. A
malformed map can therefore make one bucket reuse another bucket's
workspace by encoding an id different from -1 - slot.
For uniform buckets, the second replica selection expands the source
bucket's permutation into that aliased workspace buffer. If the source
bucket is larger than the aliased bucket, the write runs past the smaller
permutation array and can escape the kvmalloc'd CRUSH workspace. KASAN
reports a slab OOB write of 4 bytes in bucket_perm_choose().
Reject buckets whose encoded id does not match their array slot. Valid
CRUSH maps already use the canonical negative id corresponding to the
bucket slot, so this restores the invariant expected by
work->work[-1 - in->id] without changing valid map behavior. |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
list_for_each_entry() iterates ci->i_cap_flush_list but drops
i_ceph_lock to send cap messages. During the unlock window,
handle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries
with tid <= flush_tid from the list, release i_ceph_lock, and free
them via ceph_free_cap_flush() outside any lock. When the original
thread reacquires i_ceph_lock and the for-loop macro advances via
cf = list_next_entry(cf, i_list), it dereferences cf->i_list.next
on freed memory.
The race timeline:
__kick_flushing_caps() handle_cap_flush_ack()
----------------------- -----------------------
holds i_ceph_lock <---
iterates to cf (tid=10)
prepares FLUSH message
drops i_ceph_lock <---
__send_cap() ── FLUSH(tid=10)
MDS sends FLUSH_ACK(tid=10)
---> acquires i_ceph_lock
cf->tid(10) <= flush_tid(10),
detaches cf from i_cap_flush_list
drops i_ceph_lock
ceph_free_cap_flush(cf) <- frees it!
acquires i_ceph_lock <---
for-loop advances:
cf = list_next_entry(cf, i_list)
-- UAF on freed cf->i_list.next
The cf was just sent by __kick_flushing_caps itself via __send_cap().
The MDS may respond with FLUSH_ACK quickly enough that
handle_cap_flush_ack() frees cf before __kick_flushing_caps can
finish the iteration.
Fix by converting to a manual while loop: save the next pointer
under i_ceph_lock before dropping it, then use the saved pointer
after reacquiring, so the potentially-freed cf is never accessed again. |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: fix UAF in check_new_map() on session freed during unlock
check_new_map() iterates mdsc->sessions[] and for each active session
drops mdsc->mutex to perform per-session operations. The forced-close
path (rank removed from map) correctly takes a reference on s via
ceph_get_mds_session() before releasing mdsc->mutex, but three other
paths do not:
Path A (address changed): mutex_unlock → mutex_lock(&s->s_mutex)
Path B (reconnect): mutex_unlock → send_mds_reconnect(mdsc, s)
Path C (active transition): mutex_unlock → mutex_lock(&s->s_mutex)
Without the extra reference, another thread can acquire mdsc->mutex
during the unlock window, call __unregister_session() which drops the
last reference on s, and free it. The original thread then accesses
freed memory via s->s_mutex.
Fix by adding ceph_get_mds_session(s) before each mutex_unlock and
ceph_put_mds_session(s) after the corresponding mutex_lock, matching
the pattern already used in the forced-close path.
Race timeline (Path A):
Thread A (check_new_map) Thread B (another map update
holds mdsc->mutex or session teardown)
-------------------------- --------------------------
s = mdsc->sessions[i]
(refcount == 1, held only by
sessions[] array)
mutex_unlock(&mdsc->mutex)
---> acquires mdsc->mutex
__unregister_session(mdsc, s)
sessions[i] = NULL
ceph_put_mds_session(s)
refcount: 1 -> 0
kfree(s) <--- freed!
mutex_lock(&s->s_mutex)
UAF on freed s->s_mutex |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: reject export_targets ranks >= CEPH_MAX_MDS in mdsmap decode
MDSMap export_targets entries are monitor controlled. check_new_map()
uses each entry as a bit number in a fixed stack bitmap, so a rank
outside the protocol namespace can make set_bit() write past the end of
the array.
Reject ranks outside CEPH_MAX_MDS while decoding the map. Do not
validate against possible_max_rank here because maps may legitimately
reference ranks beyond a temporarily reduced max_mds. |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: bound copied dentry name length in NFS export get_name
ceph_get_name() copies the MDS-supplied name into the caller's
NAME_MAX-sized buffer with memcpy(name, rinfo->dname, rinfo->dname_len)
and then writes name[rinfo->dname_len] = 0, without checking dname_len
against NAME_MAX. A malicious or buggy MDS that returns a LOOKUPNAME reply
with dname_len > NAME_MAX overflows the buffer. __get_snap_name() copies
rde->name / rde->name_len the same unchecked way.
Impact: a malicious or compromised Ceph MDS overflows the NAME_MAX name
buffer in a client's NFS-export get_name path, a slab out-of-bounds write
reported by KASAN. Reachable when a CephFS mount is re-exported over NFS.
Add ceph_export_copy_name(), which rejects lengths above NAME_MAX with
-ENAMETOOLONG before the copy, and use it in both ceph_get_name() and
__get_snap_name(). |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: bound MDSCapAuth path and fs_name decode in handle_session()
handle_session() decodes the MDSCapAuth records carried by a
CEPH_SESSION_OPEN message (msg_version >= 6). For each record the
match.path and match.fs_name byte strings are read by first decoding a
32-bit length and then copying that many bytes with the bare
ceph_decode_copy(). Unlike the surrounding fields, which all use the
_safe decode variants, these two copies are not preceded by a
ceph_decode_need() bounds check, and the enclosing MDSCapAuth and
MDSCapMatch struct_len fields are skipped rather than enforced as an
upper bound. A length larger than the bytes remaining in the message
front makes ceph_decode_copy() read past the end of the front buffer.
The message front is a dedicated allocation (ceph_msg_new2() ->
kvmalloc), so the over-read runs off that object. A malicious or
compromised MDS can trigger this with the first post-connect message on
mount, with no client-side user interaction; under KASAN it is reported
as a slab-out-of-bounds read in handle_session().
Impact: a malicious MDS can force the kernel client to read up to 4 GiB
past the message front allocation during session setup, crashing the
client (out-of-bounds read).
Switch both copies to ceph_decode_copy_safe(), which performs the
ceph_decode_need() bounds check before the copy and branches to the
existing bad label, matching the rest of the decoder and the error path
that frees the partially decoded cap_auths array. |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: bound num_export_targets array for mds info v2/v3
ceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from
each per-mds info record and advances the decode cursor by
num_export_targets * sizeof(u32) without first checking that many bytes
remain. The only upper-bound check that catches a runaway cursor
(*p > info_end) is gated on info_v >= 4, because info_end is left NULL
for info_v 2 and 3. When the monitor sends an MDS map whose per-mds
info version is 2 or 3 with an oversized num_export_targets, the cursor
moves past the message front buffer and the later export-targets loop
calls the unchecked ceph_decode_32() on out-of-bounds memory.
A kernel client processes CEPH_MSG_MDS_MAP from its monitor session
(net/ceph/mon_client.c dispatches it; fs/ceph/super.c routes it to
ceph_mdsc_handle_mdsmap(), which sets end to the front buffer bound and
calls ceph_mdsmap_decode()). A malicious or compromised monitor, or an
on-path attacker on an unsigned/unencrypted messenger session, can
therefore drive an out-of-bounds read in the client kernel; on x86_64
with KASAN it is reported as a slab-out-of-bounds read in
ceph_mdsmap_decode(). The decoded values land in the internal
info->export_targets[] array, so the consequence is a kernel
out-of-bounds read, not an information leak to the attacker.
Impact: a malicious or compromised Ceph monitor sending an MDS map with
a per-mds info version of 2 or 3 and an oversized num_export_targets
field triggers an out-of-bounds read in the CephFS client kernel.
Add a ceph_decode_need() for the export-targets array before advancing
the cursor, so the bound is enforced for every info_v >= 2, not only
info_v >= 4. This mirrors the count-then-need idiom already used for
m_data_pg_pools later in the same function.
Compute the export-targets byte count with size_mul() and reuse that
checked length when advancing the cursor, so the attacker-controlled
num_export_targets multiplication fails closed on overflow rather than
relying on the later kcalloc() guard. |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: bound xattr value length in __build_xattrs()
__build_xattrs() decodes the MDS-supplied xattr blob one attribute at a
time. For each attribute it reads a 32-bit name length, advances past the
name bytes, reads a 32-bit value length, records the value pointer, and
advances past the value bytes. The two length fields are read with
ceph_decode_32_safe(), but the value bytes themselves are advanced over
with a bare "p += len" and no ceph_decode_need() check that "len" bytes
remain in the blob.
For every attribute except the last, the next iteration's
ceph_decode_32_safe() on the following name length implicitly verifies
that the previous value did not run past the blob end. The final
attribute has no successor, so its decoded value length is never checked
against the blob bounds. A malicious or compromised metadata server can
set the last attribute's value length larger than the bytes actually
present in the blob.
The blob is a dedicated kvmalloc() allocation sized to the wire length
(ceph_buffer_new() in ceph_fill_inode()). __set_xattr() records the
oversized length in xattr->val_len verbatim, and a later getxattr(2) runs
memcpy(value, xattr->val, xattr->val_len) into a user-supplied buffer,
copying bytes past the end of the allocation back to user space.
Impact: a malicious metadata server discloses adjacent kernel heap bytes
to a local user via getxattr(2) on a CephFS file. Add the missing
ceph_decode_need() so an out-of-bounds value length on the final
attribute fails the decode and returns -EIO instead of being stored. |
| In the Linux kernel, the following vulnerability has been resolved:
ceph: cap delegated inode count in ceph_parse_deleg_inos()
ceph_parse_deleg_inos() decodes interval sets of delegated inode numbers
from an MDS create-with-delegation reply. For each set it reads a 64-bit
start and a 64-bit len with ceph_decode_64_safe(), which only validates
that the eight bytes are present in the message, not the value, and then
loops over len while inserting entries into s_delegated_inos.
len is fully attacker controlled. A malicious or compromised MDS can send
one huge interval, many intervals in one reply, duplicate intervals, or
repeated replies that accumulate delegated inodes on the same session.
The original code bounded none of these and could spin the insert loop or
grow the xarray without limit.
Bound both dimensions with a single enforcement point. Track the number
of delegated inodes held by each MDS session in an atomic counter and
grow it only in ceph_insert_deleg_ino(), which uses atomic_add_unless()
to refuse to push the count past CEPH_MAX_DELEG_INOS. Because that helper
is the only place the counter grows, the per-session population can never
exceed the cap, so no separate per-session pre-check is needed. The
counter is decremented when async create consumes a delegated inode or
when an insert fails, incremented when a delegated inode is restored,
initialized with the session xarray, and reset when reconnect destroys
the xarray.
A per-session cap alone still lets one reply spin the insert loop on
duplicate ranges without growing the counter, so also cap the aggregate
interval length accepted from a single reply. Together these bound both
the loop trip count per reply and the xarray population across replies.
The cap is a fixed, client-chosen constant rather than a value derived
from the MDS. mds_client_prealloc_inos is a userspace MDS configuration
option; it is never sent to the kernel client on the wire, and a
server-supplied bound could not be trusted for a defensive limit in any
case. The constant is set well above that option's documented default of
1000 (a generous multiple), so legitimate refill behavior is unaffected
while the CPU and xarray memory a malformed delegation stream can consume
stays bounded.
Impact: a malicious or compromised Ceph MDS can no longer make a client
spin through an unbounded delegated-inode interval or grow one session's
delegated-inode xarray without limit. |
