kernel/linux.git/fs/smb, branch v6.18.34

ksmbd: fix durable reconnect error path file lifetime

2026-06-01T15:51:08+00:00

[ Upstream commit 3515503322f4819277091839eed46b695096aca5 ] After a durable reconnect succeeds, ksmbd_reopen_durable_fd() republishes the same ksmbd_file into the session volatile-id table. If smb2_open() then takes a later error path, cleanup first calls ksmbd_fd_put(work, fp) and then unconditionally calls ksmbd_put_durable_fd(dh_info.fp). In this case fp and dh_info.fp are the same object. The first put drops the reconnect lookup reference, but the final durable put can run __ksmbd_close_fd(NULL, fp). Because the final close is not session-aware, it can free the file object without removing the volatile-id entry that was just published into the session table. Use the session-aware put for the final reconnect drop when the reconnect had already succeeded and the error path is cleaning up the republished file. Earlier reconnect failures, before fp is assigned to dh_info.fp, keep using the durable-only put path. Fixes: 1baff47b81f9 ("ksmbd: fix use-after-free in smb2_open during durable reconnect") Signed-off-by: Junyi Liu Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin

cifs: Fix busy dentry used after unmounting

2026-06-01T15:50:45+00:00

commit c68337442f03953237a94577beb468ab2662a851 upstream. Since commit 340cea84f691c ("cifs: open files should not hold ref on superblock"), cifs file only holds the dentry ref_cnt, the cifs file close work(cfile->deferred) could be executed after unmounting, which will trigger a warning in generic_shutdown_super: BUG: Dentry 00000000a14a6845{i=c,n=file} still in use (1) [unmount of cifs cifs] The detailed processs is: process A process B kworker fd = open(PATH) vfs_open file->__f_path = *path // dentry->d_lockref.count = 1 cifs_open cifs_new_fileinfo cfile->dentry = dget(dentry) // dentry->d_lockref.count = 2 close(fd) __fput cifs_close queue_delayed_work(deferredclose_wq, cfile->deferred) dput(dentry) // dentry->d_lockref.count = 1 smb2_deferred_work_close _cifsFileInfo_put list_del(&cifs_file->flist) umount cleanup_mnt deactivate_super cifs_kill_sb cifs_close_all_deferred_files_sb cifs_close_all_deferred_files // cannot find cfile, skip _cifsFileInfo_put kill_anon_super generic_shutdown_super shrink_dcache_for_umount umount_check WARN ! // dentry->d_lockref.count = 1 cifsFileInfo_put_final dput(cifs_file->dentry) // dentry->d_lockref.count = 0 Fix it by flushing 'deferredclose_wq' before calling kill_anon_super. Fetch a reproducer in https://bugzilla.kernel.org/show_bug.cgi?id=221548. Fixes: 340cea84f691c ("cifs: open files should not hold ref on superblock") Cc: stable@vger.kernel.org Reviewed-by: Shyam Prasad N Signed-off-by: Zhihao Cheng Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb/server: promote S_DEL_ON_CLS to S_DEL_PENDING when close

2026-06-01T15:50:40+00:00

commit 4ec9c8e023c79f613fe4d5ad8cc737112efb2e44 upstream. Reproducer: 1. server: systemctl start ksmbd 2. client: mount -t cifs //${server_ip}/export /mnt 3. client: C program: openat(AT_FDCWD, "/mnt", O_RDWR | O_TMPFILE, 0600) Do not treat `FILE_DELETE_ON_CLOSE_LE` as delete pending while files remain open. This patch fixes xfstests generic/004. Cc: stable@vger.kernel.org Link: https://chenxiaosong.com/en/smb-xfstests-generic-004.html Co-developed-by: Huiwen He Signed-off-by: Huiwen He Signed-off-by: ChenXiaoSong Tested-by: Steve French Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb: client: use data_len for SMB2 READ encrypted folioq copy

2026-06-01T15:50:40+00:00

commit d4d76c9ee1997cc8c977a63f6c43551c253c1066 upstream. In handle_read_data() the encrypted/folioq branch (buf_len <= data_offset, reached via receive_encrypted_read for transform PDUs > CIFSMaxBufSize + MAX_HEADER_SIZE) copies the READ payload using buffer_len rather than data_len: rdata->result = cifs_copy_folioq_to_iter(buffer, buffer_len, cur_off, &rdata->subreq.io_iter); ... rdata->got_bytes = buffer_len; buffer_len comes from the SMB3 transform header OriginalMessageSize field (OriginalMessageSize - read_rsp_size); it represents the size of the decrypted message after the SMB2 header. data_len comes from the SMB2 READ response DataLength field; it represents the actual READ payload size and may be smaller than buffer_len when the decrypted message contains padding or other trailing bytes after the READ payload. The existing check `data_len > buffer_len - pad_len` only enforces an upper bound, so a server that emits OriginalMessageSize larger than read_rsp_size + pad_len + data_len passes the check and the kernel copies buffer_len bytes per response, ignoring the server-asserted DataLength. Two observable failures with a crafted server (DataLength=4, buffer_len=20000): - the kernel returns 20000 bytes per sub-request to userspace and sets got_bytes = buffer_len, even though the response claimed only 4 bytes of payload; - on a partial netfs sub-request whose iterator is sized to data_len, the over-large copy_folio_to_iter() short-reads, cifs_copy_folioq_to_iter() returns -EIO via the n != len path, and the entire netfs read collapses to -EIO even though the leading sub-requests succeeded. Use data_len for the copy length and for got_bytes so the kernel honours the server-asserted READ payload size. For well-formed servers (where buffer_len == pad_len + data_len) the change is behaviour-equivalent. Cc: stable@vger.kernel.org Signed-off-by: Jeremy Erazo Acked-by: David Howells Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()

2026-06-01T15:50:40+00:00

commit 4d8690dace005a38e6dbde9ecce2da3ad85c7c41 upstream. Commit 96c4af418586 ("cifs: Fix locking usage for tcon fields") refactored cifs code to change cifs_tcp_ses_lock for tc_lock around tc_count changes. There was missing lock around tc_count increment inside smb2_find_smb_sess_tcon_unlocked(). Cc: stable@vger.kernel.org Fixes: 96c4af418586 ("cifs: Fix locking usage for tcon fields") Reviewed-by: Shyam Prasad N Signed-off-by: Henrique Carvalho Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb: client: require net admin for CIFS SWN netlink

2026-06-01T15:50:40+00:00

commit d1ebfce2c1d161186a82e77590bf7da2ea1bce91 upstream. CIFS_GENL_CMD_SWN_NOTIFY is the userspace witness-notify command. The intended sender is the cifs.witness helper, but the generic-netlink operation currently has no capability flag, so any local process can send RESOURCE_CHANGE or CLIENT_MOVE notifications to the in-kernel witness handler. The same family exposes CIFS_GENL_MCGRP_SWN without multicast-group capability flags. Register messages sent to that group include the witness registration id and, for NTLM-authenticated mounts, the username, domain, and password attributes copied from the CIFS session. An unprivileged local process should not be able to join that group and receive those messages. Require CAP_NET_ADMIN for incoming SWN_NOTIFY commands with GENL_ADMIN_PERM, and require CAP_NET_ADMIN over the network namespace for joining the SWN multicast group with GENL_MCAST_CAP_NET_ADMIN. The cifs.witness service runs with the privileges needed for both operations. Fixes: fed979a7e082 ("cifs: Set witness notification handler for messages from userspace daemon") Cc: stable@vger.kernel.org Signed-off-by: Michael Bommarito Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

ksmbd: validate SID in parent security descriptor during ACL inheritance

2026-06-01T15:50:39+00:00

commit 69f030cf95488ae1186c72ac8c66fd279664ea7f upstream. Introduce smb_validate_ntsd_sid() helper to safely validate Owner SID and Group SID inside the NT Security Descriptor (smb_ntsd) retrieved from the parent directory. Cc: stable@vger.kernel.org Signed-off-by: Junyi Liu Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

ksmbd: fix SID memory leak in set_posix_acl_entries_dacl() on overflow

2026-06-01T15:50:39+00:00

commit af92ee994cc7f7e83a41c2025f32257a2f82a7ef upstream. Commit 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow") added check_add_overflow() guards that break out of the ACE-building loops in set_posix_acl_entries_dacl() when the accumulated DACL size would wrap past 65535. However, each iteration allocates a struct smb_sid via kmalloc_obj() at the top of the loop and relies on the kfree(sid) call at the end of the loop body (the 'pass_same_sid' label in the first loop, and the explicit kfree at the tail of the second loop) to release it. The newly introduced 'break' statements bypass those kfree() calls, leaking the sid buffer every time an overflow is detected. A malicious or malformed file with enough POSIX ACL entries to trip the overflow check will leak one or more struct smb_sid allocations on every request that touches the file's DACL, providing a trivial kernel memory exhaustion vector. Free sid before breaking out of the loops to plug the leak. Fixes: 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow") Cc: stable@vger.kernel.org Signed-off-by: Ferry Meng Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

ksmbd: fix null pointer dereference in compare_guid_key()

2026-06-01T15:50:39+00:00

commit 4b83cbc4c15f09b000cc06f033f64b0824b6dc87 upstream. session_fd_check() walks the per-inode m_op_list during durable-handle session teardown and sets op->conn = NULL for every opinfo whose conn matched the closing session's connection. The matching opinfo, however, stays linked in its per-ClientGuid lease_table_list entry's lb->lease_list because destroy_lease_table() only runs on full TCP-connection teardown, not on SESSION_LOGOFF. If the same TCP connection then negotiates a fresh session with the same ClientGuid (ClientGuid is bound to NEGOTIATE, not the session, and is unchanged across LOGOFF + SETUP) and issues a SMB2 CREATE with a lease context on a different inode, find_same_lease_key() walks lb->lease_list, reaches the stale opinfo, and calls compare_guid_key(), which unconditionally dereferences opinfo->conn->ClientGUID. The conn pointer is NULL and the kernel panics. Reproducer requires only a successful SMB2 SESSION_SETUP and a share configured with 'durable handles = yes'. KASAN report on mainline 70390501d194: general protection fault, probably for non-canonical address 0xdffffc0000000069: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000348-0x000000000000034f] Workqueue: ksmbd-io handle_ksmbd_work RIP: 0010:bcmp+0x5b/0x230 Call Trace: compare_guid_key+0x4b/0xd0 find_same_lease_key+0x324/0x690 smb2_open+0x6aea/0x8e60 handle_ksmbd_work+0x796/0xee0 ... Faulting address 0x348 is the offset of ClientGUID within struct ksmbd_conn, confirming opinfo->conn was NULL. Read opinfo->conn once and bail out if it has been cleared by a concurrent session_fd_check(). A half-detached opinfo cannot be the owner of an active lease, so returning 0 is the correct match result. Fixes: c8efcc786146 ("ksmbd: add support for durable handles v1/v2") Cc: stable@vger.kernel.org Signed-off-by: Jeremy Laratro Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb: client: reject userspace cifs.spnego descriptions

2026-06-01T15:50:38+00:00

commit 3da1fdf4efbc490041eb4f836bf596201203f8f2 upstream. cifs.spnego key descriptions contain authority-bearing fields such as pid, uid, creduid, and upcall_target that cifs.upcall treats as kernel-originating inputs. However, userspace can also create keys of this type through request_key(2) or add_key(2), allowing those fields to be supplied without CIFS origin. Only accept cifs.spnego descriptions while CIFS is using its private spnego_cred to request the key. Fixes: f1d662a7d5e5 ("[CIFS] Add upcall files for cifs to use spnego/kerberos") Assisted-by: avom-custom-harness:gpt-5.5-qwen3.6-mod-mix Reviewed-by: David Howells Signed-off-by: Asim Viladi Oglu Manizada Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman