kernel/linux.git/fs/smb/client, branch v6.12.92

cifs: Fix busy dentry used after unmounting

2026-06-01T15:46:20+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: client: use data_len for SMB2 READ encrypted folioq copy

2026-06-01T15:46:17+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()

2026-06-01T15:46:17+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

2026-06-01T15:46:16+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

smb: client: reject userspace cifs.spnego descriptions

2026-06-01T15:46:15+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

smb: client: Use FullSessionKey for AES-256 encryption key derivation

2026-05-23T11:05:01+00:00

[ Upstream commit 5be7a0cef3229fb3b63a07c0d289daf752545424 ] When Kerberos authentication is used with AES-256 encryption (AES-256-CCM or AES-256-GCM), the SMB3 encryption and decryption keys must be derived using the full session key (Session.FullSessionKey) rather than just the first 16 bytes (Session.SessionKey). Per MS-SMB2 section 3.2.5.3.1, when Connection.Dialect is "3.1.1" and Connection.CipherId is AES-256-CCM or AES-256-GCM, Session.FullSessionKey must be set to the full cryptographic key from the GSS authentication context. The encryption and decryption key derivation (SMBC2SCipherKey, SMBS2CCipherKey) must use this FullSessionKey as the KDF input. The signing key derivation continues to use Session.SessionKey (first 16 bytes) in all cases. Previously, generate_key() hardcoded SMB2_NTLMV2_SESSKEY_SIZE (16) as the HMAC-SHA256 key input length for all derivations. When Kerberos with AES-256 provides a 32-byte session key, the KDF for encryption/decryption was using only the first 16 bytes, producing keys that did not match the server's, causing mount failures with sec=krb5 and require_gcm_256=1. Add a full_key_size parameter to generate_key() and pass the appropriate size from generate_smb3signingkey(): - Signing: always SMB2_NTLMV2_SESSKEY_SIZE (16 bytes) - Encryption/Decryption: ses->auth_key.len when AES-256, otherwise 16 Also fix cifs_dump_full_key() to report the actual session key length for AES-256 instead of hardcoded CIFS_SESS_KEY_SIZE, so that userspace tools like Wireshark receive the correct key for decryption. Cc: Reviewed-by: Bharath SM Signed-off-by: Piyush Sachdeva Signed-off-by: Piyush Sachdeva Signed-off-by: Steve French [ adapted upstream's void/hmac_sha256_init_usingrawkey-based generate_key() to 6.12's int-return crypto_shash_* form while threading full_key_size through all callers. ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

smb/client: fix possible infinite loop and oob read in symlink_data()

2026-05-23T11:04:59+00:00

commit 7d9a7f1f96cd617ee9e75bb22217c709038e26b8 upstream. On 32-bit architectures, the infinite loop is as follows: len = p->ErrorDataLength == 0xfffffff8 u8 *next = p->ErrorContextData + len next == p On 32-bit architectures, the out-of-bounds read is as follows: len = p->ErrorDataLength == 0xfffffff0 u8 *next = p->ErrorContextData + len next == (u8 *)p - 8 Reported-by: ChenXiaoSong Fixes: 76894f3e2f71 ("cifs: improve symlink handling for smb2+") Cc: stable@vger.kernel.org Signed-off-by: Ye Bin Reviewed-by: ChenXiaoSong Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb: client: fix OOB reads parsing symlink error response

2026-05-23T11:04:57+00:00

[ Upstream commit 3df690bba28edec865cf7190be10708ad0ddd67e ] When a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message() returns success without any length validation, leaving the symlink parsers as the only defense against an untrusted server. symlink_data() walks SMB 3.1.1 error contexts with the loop test "p < end", but reads p->ErrorId at offset 4 and p->ErrorDataLength at offset 0. When the server-controlled ErrorDataLength advances p to within 1-7 bytes of end, the next iteration will read past it. When the matching context is found, sym->SymLinkErrorTag is read at offset 4 from p->ErrorContextData with no check that the symlink header itself fits. smb2_parse_symlink_response() then bounds-checks the substitute name using SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from iov_base. That value is computed as sizeof(smb2_err_rsp) + sizeof(smb2_symlink_err_rsp), which is correct only when ErrorContextCount == 0. With at least one error context the symlink data sits 8 bytes deeper, and each skipped non-matching context shifts it further by 8 + ALIGN(ErrorDataLength, 8). The check is too short, allowing the substitute name read to run past iov_len. The out-of-bound heap bytes are UTF-16-decoded into the symlink target and returned to userspace via readlink(2). Fix this all up by making the loops test require the full context header to fit, rejecting sym if its header runs past end, and bound the substitute name against the actual position of sym->PathBuffer rather than a fixed offset. Because sub_offs and sub_len are 16bits, the pointer math will not overflow here with the new greater-than. Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: stable Reviewed-by: Paulo Alcantara (Red Hat) Assisted-by: gregkh_clanker_t1000 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Steve French Signed-off-by: Alva Lan Signed-off-by: Sasha Levin

smb: client: correctly handle ErrorContextData as a flexible array

2026-05-23T11:04:57+00:00

[ Upstream commit 215b7f9ecb8d7c14d56febdcdd246f3579c32aba ] The `smb2_symlink_err_rsp` structure was previously defined with `ErrorContextData` as a single `__u8` byte. However, the `ErrorContextData` field is intended to be a variable-length array based on `ErrorDataLength`. This mismatch leads to incorrect pointer arithmetic and potential memory access issues when processing error contexts. Updates the `ErrorContextData` field to be a flexible array (`__u8 ErrorContextData[]`). Additionally, it modifies the corresponding casts in the `symlink_data()` function to properly handle the flexible array, ensuring correct memory calculations and data handling. These changes improve the robustness of SMB2 symlink error processing. Signed-off-by: Liang Jie Suggested-by: Tom Talpey Signed-off-by: Steve French Signed-off-by: Alva Lan Signed-off-by: Sasha Levin

smb: client: validate dacloffset before building DACL pointers

2026-05-14T13:29:25+00:00

commit f98b48151cc502ada59d9778f0112d21f2586ca3 upstream. parse_sec_desc(), build_sec_desc(), and the chown path in id_mode_to_cifs_acl() all add the server-supplied dacloffset to pntsd before proving a DACL header fits inside the returned security descriptor. On 32-bit builds a malicious server can return dacloffset near U32_MAX, wrap the derived DACL pointer below end_of_acl, and then slip past the later pointer-based bounds checks. build_sec_desc() and id_mode_to_cifs_acl() can then dereference DACL fields from the wrapped pointer in the chmod/chown rewrite paths. Validate dacloffset numerically before building any DACL pointer and reuse the same helper at the three DACL entry points. Fixes: bc3e9dd9d104 ("cifs: Change SIDs in ACEs while transferring file ownership.") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Michael Bommarito Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman