From: Michael Bommarito <michael.bommarito@gmail.com> mainline inclusion from mainline-v7.3-rc1 commit 4bd3158bd62466d57ed72a3f7bc5f205fedd6919 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/18927 CVE: CVE-2026-89648 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- 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. Cc: stable@vger.kernel.org Fixes: d48464878708 ("ceph: decode interval_sets for delegated inos") Suggested-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com> Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com> Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Conflicts: fs/ceph/mds_client.c [backport to OLK-5.10: context adjusted for this tree: pr_warn_ratelimited_client()/doutc() from 38d46409c4639 are not used here, so the new warnings use plain pr_warn_ratelimited() and the struct ceph_client *cl local is not added. The redundant 'ino' local (2ecd0edd13a8b not applied here) is dropped together with its only user, the open-coded xa_insert() in ceph_parse_deleg_inos(). CEPH_MAX_DELEG_INOS is inserted right after CEPH_INO_SYSTEM_BASE. s_num_deleg_inos is reset next to the existing xa_destroy() in send_mds_reconnect(), which still runs before mutex_lock(&session->s_mutex) in this tree (39fe30315893 not applied); this matches the linux-6.18.y stable backport c040e139f1a62.] Signed-off-by: Pan Taixi <pantaixi1@huawei.com> --- fs/ceph/mds_client.c | 58 ++++++++++++++++++++++++++++++++++++++------ fs/ceph/mds_client.h | 1 + fs/ceph/super.h | 9 +++++++ 3 files changed, 61 insertions(+), 7 deletions(-) diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index aea1b42b9b18..ef39852280c8 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -419,39 +419,80 @@ static int parse_reply_info_filelock(void **p, void *end, #if BITS_PER_LONG == 64 #define DELEGATED_INO_AVAILABLE xa_mk_value(1) +static int ceph_insert_deleg_ino(struct ceph_mds_session *s, u64 ino) +{ + int err; + + /* + * Cap how many delegated inodes a single session may hold. This is + * the only place that grows the count, so atomic_add_unless() bounds + * it at exactly CEPH_MAX_DELEG_INOS; s_num_deleg_inos can never exceed + * that. + */ + if (!atomic_add_unless(&s->s_num_deleg_inos, 1, CEPH_MAX_DELEG_INOS)) { + pr_warn_ratelimited("MDS session already holds %d delegated inodes\n", + CEPH_MAX_DELEG_INOS); + return -EOVERFLOW; + } + + err = xa_insert(&s->s_delegated_inos, ino, DELEGATED_INO_AVAILABLE, + GFP_KERNEL); + if (err) + atomic_dec(&s->s_num_deleg_inos); + return err; +} + static int ceph_parse_deleg_inos(void **p, void *end, struct ceph_mds_session *s) { + u64 msg_deleg_inos = 0; u32 sets; ceph_decode_32_safe(p, end, sets, bad); dout("got %u sets of delegated inodes\n", sets); while (sets--) { - u64 start, len, ino; + u64 start, len; ceph_decode_64_safe(p, end, start, bad); ceph_decode_64_safe(p, end, len, bad); /* Don't accept a delegation of system inodes */ if (start < CEPH_INO_SYSTEM_BASE) { pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n", start, len); continue; } + + /* + * Bound the number of inodes one reply may delegate. + * ceph_insert_deleg_ino() separately caps the per-session + * population, so this only has to stop one reply from spinning + * the insert loop under an attacker-controlled len. + */ + if (len > (u64)CEPH_MAX_DELEG_INOS || + msg_deleg_inos > (u64)CEPH_MAX_DELEG_INOS - len) { + pr_warn_ratelimited("MDS reply delegates too many inodes (have %llu, +%llu, max %d)\n", + msg_deleg_inos, len, CEPH_MAX_DELEG_INOS); + return -EIO; + } + msg_deleg_inos += len; + while (len--) { - int err = xa_insert(&s->s_delegated_inos, ino = start++, - DELEGATED_INO_AVAILABLE, - GFP_KERNEL); + int err = ceph_insert_deleg_ino(s, start++); + if (!err) { dout("added delegated inode 0x%llx\n", start - 1); } else if (err == -EBUSY) { pr_warn("ceph: MDS delegated inode 0x%llx more than once.\n", start - 1); + } else if (err == -EOVERFLOW) { + /* ceph_insert_deleg_ino() already warned. */ + return -EIO; } else { return err; } } } @@ -465,20 +506,21 @@ u64 ceph_get_deleg_ino(struct ceph_mds_session *s) unsigned long ino; void *val; xa_for_each(&s->s_delegated_inos, ino, val) { val = xa_erase(&s->s_delegated_inos, ino); - if (val == DELEGATED_INO_AVAILABLE) + if (val == DELEGATED_INO_AVAILABLE) { + atomic_dec(&s->s_num_deleg_inos); return ino; + } } return 0; } int ceph_restore_deleg_ino(struct ceph_mds_session *s, u64 ino) { - return xa_insert(&s->s_delegated_inos, ino, DELEGATED_INO_AVAILABLE, - GFP_KERNEL); + return ceph_insert_deleg_ino(s, ino); } #else /* BITS_PER_LONG == 64 */ /* * FIXME: xarrays can't handle 64-bit indexes on a 32-bit arch. For now, just * ignore delegated_inos on 32 bit arch. Maybe eventually add xarrays for top @@ -760,10 +802,11 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc, s->s_nr_caps = 0; refcount_set(&s->s_ref, 1); INIT_LIST_HEAD(&s->s_waiting); INIT_LIST_HEAD(&s->s_unsafe); xa_init(&s->s_delegated_inos); + atomic_set(&s->s_num_deleg_inos, 0); s->s_num_cap_releases = 0; s->s_cap_reconnect = 0; s->s_cap_iterator = NULL; INIT_LIST_HEAD(&s->s_cap_releases); INIT_WORK(&s->s_cap_release_work, ceph_cap_release_work); @@ -3908,10 +3951,11 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc, reply = ceph_msg_new2(CEPH_MSG_CLIENT_RECONNECT, 0, 1, GFP_NOFS, false); if (!reply) goto fail_nomsg; xa_destroy(&session->s_delegated_inos); + atomic_set(&session->s_num_deleg_inos, 0); mutex_lock(&session->s_mutex); session->s_state = CEPH_MDS_SESSION_RECONNECTING; session->s_seq = 0; diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h index b1939f916228..847f04424be3 100644 --- a/fs/ceph/mds_client.h +++ b/fs/ceph/mds_client.h @@ -208,10 +208,11 @@ struct ceph_mds_session { u64 s_renew_seq; struct list_head s_waiting; /* waiting requests */ struct list_head s_unsafe; /* unsafe requests */ struct xarray s_delegated_inos; + atomic_t s_num_deleg_inos; }; /* * modes of choosing which MDS to send a request to */ diff --git a/fs/ceph/super.h b/fs/ceph/super.h index c0c5ed3e2718..6b2e0cfb9ae3 100644 --- a/fs/ceph/super.h +++ b/fs/ceph/super.h @@ -538,10 +538,19 @@ static inline int ceph_ino_compare(struct inode *inode, void *data) #define CEPH_MAX_MDS 0x100 #define CEPH_NUM_STRAY 10 #define CEPH_MDS_INO_MDSDIR_OFFSET (1 * CEPH_MAX_MDS) #define CEPH_INO_SYSTEM_BASE ((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY)) +/* + * Upper bound on the number of delegated inodes a single MDS session may + * hold. The MDS normally hands out a small preallocation window (the + * userspace mds_client_prealloc_inos option defaults to 1000) and refills + * it as the client consumes entries. This leaves generous headroom while + * bounding the CPU and memory a malformed delegation interval can consume. + */ +#define CEPH_MAX_DELEG_INOS 8192 + static inline bool ceph_vino_is_reserved(const struct ceph_vino vino) { if (vino.ino < CEPH_INO_SYSTEM_BASE && vino.ino >= CEPH_MDS_INO_MDSDIR_OFFSET) { WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino); -- 2.34.1