From b003086d76968298f22e7cf62239833b5a3a06b1 Mon Sep 17 00:00:00 2001 From: Gil Portnoy Date: Thu, 28 May 2026 00:00:00 +0000 Subject: [PATCH 1/3] ksmbd: fix NULL-deref of opinfo->conn in oplock/lease break notifiers smb2_oplock_break_noti() and smb2_lease_break_noti() read opinfo->conn into a local with neither READ_ONCE() nor a NULL check. Both run from oplock_break() after opinfo_get_list() has dropped ci->m_lock, so a concurrent SMB2 LOGOFF (session_fd_check()) can set op->conn = NULL under ci->m_lock within that window. ksmbd_conn_r_count_inc(conn) then writes through NULL at offset 0xc4 -- a remotely triggerable oops. Guard both reads the way compare_guid_key() already does: read opinfo->conn with READ_ONCE() and return early if it is NULL, before allocating the work struct so nothing leaks. A NULL conn means the client is gone and the break is moot, so return 0; oplock_break() treats that as success and runs the normal teardown. Fixes: c8efcc786146 ("ksmbd: add support for durable handles v1/v2") Assisted-by: Henry (Claude):claude-opus-4 Signed-off-by: Gil Portnoy Acked-by: Namjae Jeon Signed-off-by: Steve French --- fs/smb/server/oplock.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/fs/smb/server/oplock.c b/fs/smb/server/oplock.c index 0f5c18520eff..b193dde4810d 100644 --- a/fs/smb/server/oplock.c +++ b/fs/smb/server/oplock.c @@ -711,11 +711,16 @@ static void __smb2_oplock_break_noti(struct work_struct *wk) */ static int smb2_oplock_break_noti(struct oplock_info *opinfo) { - struct ksmbd_conn *conn = opinfo->conn; + struct ksmbd_conn *conn; struct oplock_break_info *br_info; int ret = 0; - struct ksmbd_work *work = ksmbd_alloc_work_struct(); + struct ksmbd_work *work; + conn = READ_ONCE(opinfo->conn); + if (!conn) + return 0; + + work = ksmbd_alloc_work_struct(); if (!work) return -ENOMEM; @@ -815,11 +820,15 @@ static void __smb2_lease_break_noti(struct work_struct *wk) */ static int smb2_lease_break_noti(struct oplock_info *opinfo) { - struct ksmbd_conn *conn = opinfo->conn; + struct ksmbd_conn *conn; struct ksmbd_work *work; struct lease_break_info *br_info; struct lease *lease = opinfo->o_lease; + conn = READ_ONCE(opinfo->conn); + if (!conn) + return 0; + work = ksmbd_alloc_work_struct(); if (!work) return -ENOMEM; From 7ce4fc40018de07f05f3035241122d992610dbfb Mon Sep 17 00:00:00 2001 From: Gil Portnoy Date: Thu, 28 May 2026 00:00:00 +0000 Subject: [PATCH 2/3] ksmbd: fix durable reconnect double-bind race in ksmbd_reopen_durable_fd Two concurrent same-user DHnC reconnects can both observe fp->conn == NULL before either sets it. ksmbd_reopen_durable_fd() checks fp->conn to guard against a handle already being reconnected, but the check and the binding assignment are not atomic: both threads pass the guard, both call ksmbd_conn_get() on the same fp, and both eventually reach kfree(fp->owner.name) -- a double-free of the owner.name slab object. The double-bound ksmbd_file also causes a write-UAF on the 344-byte ksmbd_file_cache object when a concurrent smb2_close() spins on fp->f_lock after the object has been freed by the losing reconnect path. KASAN on 7.1-rc5 (48-thread concurrent reconnect, 3000 cycles): BUG: KASAN: double-free in ksmbd_reopen_durable_fd+0x268/0x308 BUG: KASAN: slab-use-after-free in _raw_spin_lock+0xac/0x150 Write of size 4 at offset 24 into freed ksmbd_file_cache object Five double-bind windows observed; 63 total KASAN reports triggered. Fix: validate and claim fp->conn under write_lock(&global_ft.lock) so the check-and-claim is atomic. ksmbd_lookup_durable_fd() already treats fp->conn != NULL as "in use" and skips such an fp; setting fp->conn before dropping the lock closes the race. ksmbd_conn_get() is a non-sleeping refcount increment, safe under the rwlock. The rollback path on __open_id() failure also clears fp->conn/tcon under the lock so concurrent readers see a consistent state. Fixes: b1f1e80620de ("ksmbd: centralize ksmbd_conn final release to plug transport leak") Assisted-by: Henry (Claude):claude-opus-4 Signed-off-by: Gil Portnoy Acked-by: Namjae Jeon Signed-off-by: Steve French --- fs/smb/server/vfs_cache.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c index 4d2d33df6231..ba3355a6057a 100644 --- a/fs/smb/server/vfs_cache.c +++ b/fs/smb/server/vfs_cache.c @@ -1390,19 +1390,19 @@ int ksmbd_reopen_durable_fd(struct ksmbd_work *work, struct ksmbd_file *fp) struct ksmbd_lock *smb_lock; unsigned int old_f_state; + write_lock(&global_ft.lock); if (!fp->is_durable || fp->conn || fp->tcon) { + write_unlock(&global_ft.lock); pr_err("Invalid durable fd [%p:%p]\n", fp->conn, fp->tcon); return -EBADF; } if (has_file_id(fp->volatile_id)) { + write_unlock(&global_ft.lock); pr_err("Still in use durable fd: %llu\n", fp->volatile_id); return -EBADF; } - old_f_state = fp->f_state; - fp->f_state = FP_NEW; - /* * Initialize fp's connection binding before publishing fp into the * session's file table. If __open_id() is ordered first, a @@ -1413,11 +1413,17 @@ int ksmbd_reopen_durable_fd(struct ksmbd_work *work, struct ksmbd_file *fp) */ fp->conn = ksmbd_conn_get(conn); fp->tcon = work->tcon; + write_unlock(&global_ft.lock); + + old_f_state = fp->f_state; + fp->f_state = FP_NEW; __open_id(&work->sess->file_table, fp, OPEN_ID_TYPE_VOLATILE_ID); if (!has_file_id(fp->volatile_id)) { + write_lock(&global_ft.lock); fp->conn = NULL; fp->tcon = NULL; + write_unlock(&global_ft.lock); ksmbd_conn_put(conn); fp->f_state = old_f_state; return -EBADF; From f580d27e8928828693df44ba2db0fffdbe11dfea Mon Sep 17 00:00:00 2001 From: Gil Portnoy Date: Mon, 1 Jun 2026 08:27:56 +0900 Subject: [PATCH 3/3] ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL A deferred byte-range lock (an SMB2_LOCK that blocks) registers an async work on conn->async_requests via setup_async_work(), with cancel_fn = smb2_remove_blocked_lock and cancel_argv[0] pointing at the struct file_lock. When the request is cancelled, the worker frees the file_lock with locks_free_lock() and takes the cancelled early-exit, which "goto out"s and never reaches release_async_work() -- the only site that unlinks the work from conn->async_requests and clears cancel_fn/cancel_argv. The work therefore stays matchable on async_requests with a live cancel_fn pointing at the freed file_lock, until connection teardown finally runs release_async_work(). smb2_cancel() fires cancel_fn unconditionally with no state guard, so a second SMB2_CANCEL for the same AsyncId, arriving in that window, re-runs smb2_remove_blocked_lock() on the freed file_lock -- a slab use-after-free: BUG: KASAN: slab-use-after-free in __locks_delete_block __locks_delete_block locks_delete_block ksmbd_vfs_posix_lock_unblock smb2_remove_blocked_lock smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn handle_ksmbd_work Allocated by ...: locks_alloc_lock <- smb2_lock Freed by ...: locks_free_lock <- smb2_lock (cancelled branch) ... cache file_lock_cache of size 192 Reproduced on mainline with KASAN by an authenticated SMB client. Skip a work whose state is already KSMBD_WORK_CANCELLED so its cancel callback cannot be fired a second time. Cc: stable@vger.kernel.org Signed-off-by: Gil Portnoy Acked-by: Namjae Jeon Signed-off-by: Steve French --- fs/smb/server/smb2pdu.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 620bcfbbfd92..3eb3b1711acb 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -7322,6 +7322,17 @@ int smb2_cancel(struct ksmbd_work *work) le64_to_cpu(hdr->Id.AsyncId)) continue; + /* + * A cancelled deferred byte-range lock frees its + * file_lock and takes the smb2_lock() early-exit that + * skips release_async_work(), so the work stays on + * conn->async_requests with a live cancel_fn pointing + * at the freed file_lock. Re-firing it on a second + * SMB2_CANCEL is a use-after-free. + */ + if (iter->state == KSMBD_WORK_CANCELLED) + break; + ksmbd_debug(SMB, "smb2 with AsyncId %llu cancelled command = 0x%x\n", le64_to_cpu(hdr->Id.AsyncId),