kernel/linux.git/fs/smb/server, branch v6.18.44

ksmbd: reject repeated SMB2 NEGOTIATE requests

2026-08-09T18:25:15+00:00

commit cb469993b3a61a72653770856d37af616d72d05f upstream. Unauthenticated client can send multiple successful SMB2 NEGOTIATE requests on one connection before SESSION_SETUP. While the connection is in KSMBD_SESS_NEED_SETUP, smb2_handle_negotiate() accepts another SMB3.1.1 NEGOTIATE and overwrites conn->preauth_info with a new allocation. Only the final allocation is freed when the connection is released, leaking one object for every additional successful request. A repeated SMB2 NEGOTIATE after a dialect has been selected is a protocol violation. MS-SMB2 section 3.3.5.4 requires the server to disconnect without replying in this case. Set the connection exiting when rejecting the request, in addition to suppressing the response. Reject SMB2 NEGOTIATE unless the connection is new or is waiting for the SMB2 NEGOTIATE that follows an SMB1 multi-protocol negotiate. Serialize both SMB1 and SMB2 negotiation paths under conn->srv_mutex, since they update connection-wide dialect and negotiation state. Move the locking contract to ksmbd_smb_negotiate_common(), where the state and dialect are selected, and add ksmbd_conn_new() for consistent state access. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: stable@vger.kernel.org Reported-by: Runa Takemoto Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

ksmbd: fix use-after-free in __close_file_table_ids()

2026-08-09T18:25:09+00:00

[ Upstream commit e7188199eff46a636f3436356f0aae039be6dd66 ] A ksmbd_file can remain alive after logical close while another session holds a temporary reference obtained through ksmbd_lookup_fd_inode(). ksmbd_close_fd() currently marks the file closed and drops the idr-owned reference, but leaves the pointer published in the closing session's idr until the final reference is dropped. If the foreign holder performs the final ksmbd_fd_put(), __put_fd_final() supplies the foreign session's file table to __ksmbd_close_fd(). The object is then freed without being removed from its owner's idr, and the owner session later dereferences the stale pointer during file-table teardown. Remove the volatile id from the owner's idr while ksmbd_close_fd() still holds that table's lock, and clear volatile_id before dropping the idr-owned reference. A later foreign final put then only performs physical destruction and cannot remove the object from the wrong table. Fixes: 8510a043d334 ("ksmbd: increment reference count of parent fp") Reported-by: Yunseong Kim Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin

ksmbd: return success for deferred final close

2026-08-09T18:25:09+00:00

[ Upstream commit c5db4de8988f1a621556ca5c4537f77b766ca07d ] ksmbd_close_fd() marks an open file as FP_CLOSED and drops the file table reference. If another in-flight request still holds a reference, the final close is deferred until that request drops its reference. The function currently returns -EINVAL in that deferred-final-close case because fp is cleared when the reference count does not reach zero. That turns a valid close into STATUS_FILE_CLOSED. smb2.compound_find.compound_find_close sends QUERY_DIRECTORY and then closes the same directory handle before receiving the find response. The query holds a reference while it builds the response, so close must mark the handle closed and return success even though final teardown is delayed. Track whether the handle was successfully transitioned to FP_CLOSED and return success when only the final close is deferred. Signed-off-by: Namjae Jeon Signed-off-by: Steve French Stable-dep-of: e7188199eff4 ("ksmbd: fix use-after-free in __close_file_table_ids()") Signed-off-by: Sasha Levin

ksmbd: validate ACE size against SID sub-authorities

2026-08-03T09:22:08+00:00

commit 5152c6d49e3fd4e9f2e857c57527aead752f1f87 upstream. set_ntacl_dacl() validates sid.num_subauth before copying an ACE, but does not verify that the declared ACE size contains all sub-authorities described by that field. An undersized ACE can therefore be copied and later make the POSIX ACL deduplication walk inspect data beyond the copied ACE boundary. The existing initial bound check is also too small. It only ensures that the ACE size field is accessible before set_ntacl_dacl() reads sid.num_subauth farther into the input buffer. Require enough input for the fixed SID header before accessing num_subauth, reject ACEs smaller than that header, and skip ACEs whose declared size cannot contain the complete SID. This makes the validation consistent with the other ACE walk paths. Reported-by: LocalHost Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Wentao Guan Signed-off-by: Sasha Levin

ksmbd: bound DACL dedup walk to copied ACEs

2026-08-03T09:22:08+00:00

commit 58d97fcd0bf1aee694e244cc28635b9df95b543b upstream. set_ntacl_dacl() can stop copying ACEs before consuming the full input DACL when size accounting overflows. When that happens, num_aces reflects only the ACEs that were actually copied into the output DACL, but set_posix_acl_entries_dacl() still receives nt_num_aces and uses it to walk the existing ACE array during dedup. That makes the dedup walk scan past the copied ACE array and inspect buffer tail that does not contain valid ACEs. Split the two meanings currently carried by the NT ACE count. Pass the number of copied NT ACEs to bound the dedup walk, and preserve the original "input DACL had NT ACEs" state separately for the Everyone/default ACL fallback. This keeps the dedup walk aligned with the ACEs that are actually present in the rebuilt DACL. Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Wentao Guan Signed-off-by: Sasha Levin

ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL

2026-08-03T09:22:08+00:00

commit bbf0a8e931204ecdab494a88d43b0a24a04285c5 upstream. check_add_overflow() unconditionally writes the truncated sum into *d even on overflow, per its contract in include/linux/overflow.h. The four check_add_overflow() guards in set_posix_acl_entries_dacl() and set_ntacl_dacl() break out of the ACE-building loops on overflow, but the truncated *size is then consumed downstream at the end of set_ntacl_dacl(): pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size); This produces an on-wire NT ACL whose pndacl->size under-reports the bytes actually written by the preceding fill_ace_for_sid()/memcpy() calls, yielding a malformed ACL that can trigger out-of-bounds reads when re-parsed by clients or ksmbd itself. Restore *size to its pre-addition value on each overflow branch (via `*size -= ace_sz` / `size -= nt_ace_size`) so that after the break, *size once again holds the cumulative size of the successfully-written ACEs. The committed ACL is then truncated-but-self-consistent rather than malformed. The ksmbd DACL builders are the only check_add_overflow() sites found where an overflow path breaks out of a loop and the destination value is consumed afterward. The other nearby break-style cases either return -EINVAL on overflow (transport_ipc.c) or break without consuming the overflowed destination value afterward (buildid.c). Fixes: 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow") Assisted-by: atomcode:glm-5.2 Assisted-by: Codex:gpt-5.5 Cc: stable@vger.kernel.org Signed-off-by: Wentao Guan Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin

ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl

2026-08-03T09:22:08+00:00

commit 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d upstream. set_ntacl_dacl() copies each ACE from the attacker-controlled stored security descriptor verbatim into the response DACL without checking sid.num_subauth. The ACE bytes (including an unchecked num_subauth) originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE with `break` rather than an error, so parse_sec_desc() still returns success and the malformed SD reaches the xattr intact. On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() -> set_posix_acl_entries_dacl() walks the copied ACEs and reads ntace->sid.sub_auth[ntace->sid.num_subauth - 1] with num_subauth taken straight from the stored SD. Since sub_auth[] is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g. 255) drives an out-of-bounds heap read of ~1 KB with an offset fully controlled by an authenticated client. The sibling functions already gate this field: parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES) set_ntacl_dacl() is the lone inconsistent path that omits the check. Add the same num_subauth validation in set_ntacl_dacl() before copying the ACE, matching the gate already enforced by parse_dacl(). Signed-off-by: Haofeng Li Reviewed-by: ChenXiaoSong Suggested-by: Namjae Jeon Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Wentao Guan Signed-off-by: Sasha Levin

ksmbd: defer destroy_previous_session() until after NTLM authentication

2026-08-03T09:22:04+00:00

commit c74801ee524f477c174a1899782b6c3b6918d407 upstream. In ntlm_authenticate(), destroy_previous_session() is called using a user pointer resolved from the client-supplied NTLM blob username field before the NTLMv2 response is validated. An authenticated attacker can set the NTLM blob username to match a victim account and set PreviousSessionId to the victim's session ID; destroy_previous_session() destroys the victim's session while ksmbd_decode_ntlmssp_auth_blob() subsequently rejects the request with -EPERM. Move destroy_previous_session() and the prev_id assignment to after ksmbd_decode_ntlmssp_auth_blob() returns success and use sess->user rather than the pre-authentication lookup result. This matches the ordering already used by krb5_authenticate(), where destroy_previous_session() is called only after ksmbd_krb5_authenticate() returns success. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-cifs/20260702155449.3639773-1-james_montgomery@disroot.org/ Signed-off-by: James Montgomery Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

ksmbd: validate compound request size before reading StructureSize2

2026-08-03T09:21:34+00:00

[ Upstream commit 15b38176fd1530372905c602fde51fe89ec8c877 ] When ksmbd validates a compound (chained) SMB2 request, ksmbd_smb2_check_message() reads pdu->StructureSize2 without first checking that the compound element is large enough to contain it. StructureSize2 is a 2-byte field at offset 64 (__SMB2_HEADER_STRUCTURE_SIZE) from the start of each element. The compound-walking logic only guarantees that a full 64-byte SMB2 header is present for the trailing element: when NextCommand is 0, len is reduced to the number of bytes remaining after next_smb2_rcv_hdr_off. A remote client can craft a compound request whose last element has exactly 64 bytes, so the 2-byte StructureSize2 read at offset 64 extends one byte past the receive buffer, producing a slab-out-of-bounds read. BUG: KASAN: slab-out-of-bounds in ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402) Read of size 2 at addr ffff888012ae31ac by task kworker/0:1/14 The buggy address is located 172 bytes inside of allocated 173-byte region Workqueue: ksmbd-io handle_ksmbd_work Call Trace: ... kasan_report (mm/kasan/report.c:595) ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402) handle_ksmbd_work (fs/smb/server/server.c:119) process_one_work (kernel/workqueue.c:3314) worker_thread (kernel/workqueue.c:3397) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245) Reject any compound element that is too small to hold StructureSize2 before dereferencing it. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Xiang Mei (Microsoft) Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin

ksmbd: pin conn during async oplock break notification

2026-08-03T09:21:34+00:00

[ Upstream commit aa5d8f3f96aa11a4a54ce993c11ce8af11c546f9 ] smb2_oplock_break_noti() and smb2_lease_break_noti() store a ksmbd_conn pointer in an async ksmbd_work and then queue that work on ksmbd-io. The work only increments conn->r_count, which prevents teardown from passing the pending-request wait after the increment, but it does not pin the struct ksmbd_conn object. If connection teardown races with an oplock break notification, the last conn reference can be dropped before the queued worker finishes. The worker then uses the freed conn in ksmbd_conn_write() and ksmbd_conn_r_count_dec(). Take a real conn reference when publishing the conn pointer to the async work item, and drop it after the notification work has decremented r_count. Apply the same lifetime rule to lease break notification, which uses the same work->conn pattern. Fixes: 3aa660c05924 ("ksmbd: prevent connection release during oplock break notification") Signed-off-by: Qihang Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin