From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793745602; b=uAyPdJ47trgNM0kcbQs0/V25iranIbXGh6/BzyJVPckm0hJ1zm7I9kEBEcZfgLIEQtzU RHGNGKr48l8QSXdopJiy3bZZ+osv6KRIngIUpxMGmeEGSJgLwD3xAnuiTWHk+ynD8GEvf +GXrA+Li6g03i3gG2re5Sa+3pzG3kNY0tRFNTgGUvC7c0l1tg73kbLNARsBK0LB+Zfwfv TlgPg7evD/o4lsNYG4Qq/M+SxiF5V4r/ahp8GeVrgd1vlKEu/S989wTNGDWFzOXNwUL/1 RiOlTF6TDJTc09eG+VLG9RZiq15i9SR7T70oDervze5zu0L4dpP+D1/ukx6UK30Bm4w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793745602; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=3uo+GbF40ittGU5b4aE8tSaoHkm2g9tPVJco39DxaTI=; b=wSQHMUS9NgYIsfSUjrSvSzHVeC/ggzxm/XYSBYM6mXCiQVzYM1uebLRHA4kj9zwu99O7 /mZBtn+QT+j2OIA2gNxZA5savTannu9XKJKhSnQ8uJW4M/K2ACkJKzWakQB/x4tWf3KTR uvgkWEU7h0BFXfYJUZzhGQ+8yDUyd1nAjDs8RNxnzNo8vdmsLdrufu7khYIxznYtoAG6P rpxSjSRQsAVS1WFGowKvuuEjjRnzaNBK0SXyVXfeJMiXSrUV7542V/ZTGg7AMQiagmMgO VUYqwQf1iYTqpb8izdp4zjh67v135XnW1PtAp9MNPIGXgM4nbWnVqEuaRWNX7Ei5e5Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Bzn7Td7F; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1F9C2606A328 for ; Tue, 3 Nov 2026 22:40:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Bzn7Td7F Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7AF161F0093A; Tue, 3 Nov 2026 22:40:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793745602; bh=3uo+GbF40ittGU5b4aE8tSaoHkm2g9tPVJco39DxaTI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Bzn7Td7FGQzNm16RBALfgQ+Niptnt028O+iCAO3lcyGl70fKLYEqjc2n1Ppp6AjPM zz5jxog4HmBBCMQi/XX6NRp2HZ8siTvVPvfqMZf0pGHCH4l6TkwoBS8xqZISiyM+4v CpBOB90JsJA+lFY6jegLe4viljSsTNPUgHxYKPIn5VzwJvo18iqd05DZbbFOaPu4TU cyKzek6fDe3si3KP5tHYoWE7bj5eCXKV8+85HLsMUuMXmF5QVTSAwsxMLwkpqwFvp7 hm8rIDOkq6Zu3FMAl3ofqpnPGwb6zWuLpzhmbF4HW56wD5mZyGsdspSr/5O6Dhp1OO xrgtn7bjBCpFQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Ian Bridges , Namjae Jeon , Sasha Levin Subject: [PATCH 6.18.y] ksmbd: fix use-after-free after a failed durable reconnect Date: Tue, 3 Nov 2026 17:40:00 -0500 Message-ID: <20261103223847.1547301-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110350-subplot-mounted-fdcb@gregkh> References: <2026110350-subplot-mounted-fdcb@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ian Bridges [ Upstream commit 248b5819591c577727930e4e255a455235fab50a ] ksmbd_reopen_durable_fd() republishes a detached durable handle in the reconnecting session's file table and takes no reference for that entry. If smb2_open() then fails, cleanup relies on the final ksmbd_fd_put() to remove the volatile id. Two reconnects of the same handle can both take a lookup reference before either attaches it. If the one that reopens first then fails and drops its references first, the other request makes the final put through ksmbd_put_durable_fd(). That frees the handle without removing the first session's table entry, so tearing that session down writes to freed memory. BUG: KASAN: slab-use-after-free in __close_file_table_ids+0x14d/0x740 [ksmbd] Call Trace: __close_file_table_ids+0x14d/0x740 [ksmbd] ksmbd_destroy_file_table+0x76/0x100 [ksmbd] ksmbd_session_destroy+0xf8/0x480 [ksmbd] ksmbd_dispose_sessions+0x13e/0x200 [ksmbd] ksmbd_conn_sessions_cleanup+0x4c3/0x6d0 [ksmbd] Freed by task 1030: __ksmbd_close_fd+0x97d/0x1000 [ksmbd] smb2_open+0x14eb/0xd9f0 [ksmbd] Commit 3515503322f4 ("ksmbd: fix durable reconnect error path file lifetime") handles a final put made by the reconnecting request, but not one made by another holder. Remove the volatile id under the file-table lock on this error path, before the references are dropped, as ksmbd_close_fd() does on the request_open path just above. Removal then no longer depends on which holder makes the final put. The stale comment in the reconnect cleanup is updated to match. A successful reconnect is unchanged. Fixes: c8efcc786146 ("ksmbd: add support for durable handles v1/v2") Cc: stable@vger.kernel.org Signed-off-by: Ian Bridges Signed-off-by: Namjae Jeon [ sashal: Adapted the cleanup call to a braced if (fp) block because the replay and request-open cleanup branches are absent. ] Signed-off-by: Sasha Levin --- fs/smb/server/smb2pdu.c | 12 +++++++----- fs/smb/server/vfs_cache.c | 28 ++++++++++++++++++++++++++++ fs/smb/server/vfs_cache.h | 2 ++ 3 files changed, 37 insertions(+), 5 deletions(-) diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 793c219b9a610..2a27711366735 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -3893,8 +3893,11 @@ int smb2_open(struct ksmbd_work *work) if (!rsp->hdr.Status) rsp->hdr.Status = STATUS_UNEXPECTED_IO_ERROR; - if (fp) + if (fp) { + if (dh_info.reconnected && fp == dh_info.fp) + ksmbd_unpublish_reopened_fd(work, fp); ksmbd_fd_put(work, fp); + } smb2_set_err_rsp(work); ksmbd_debug(SMB, "Error response: %x\n", rsp->hdr.Status); } @@ -3902,10 +3905,9 @@ int smb2_open(struct ksmbd_work *work) if (dh_info.reconnected) { /* * If reconnect succeeded, fp was republished in the - * session file table. On a later error, ksmbd_fd_put() - * above drops the session reference; drop the durable - * lookup reference through the same session-aware path so - * final close removes the volatile id before freeing fp. + * session file table, and the error path above has + * already removed its volatile id. Drop the durable + * lookup reference through the same session-aware path. */ if (rc && fp == dh_info.fp) ksmbd_fd_put(work, dh_info.fp); diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c index 5aa46e41ac6f8..bde487fb30054 100644 --- a/fs/smb/server/vfs_cache.c +++ b/fs/smb/server/vfs_cache.c @@ -486,6 +486,34 @@ static void set_close_state_blocked_works(struct ksmbd_file *fp) spin_unlock(&fp->f_lock); } +/** + * ksmbd_unpublish_reopened_fd() - remove a reopened durable handle from the + * session file table after its CREATE failed + * @work: smb work of the failed CREATE + * @fp: durable handle republished by ksmbd_reopen_durable_fd() + * + * The reopen publishes @fp in this session's table without taking a reference + * for the entry, so the CREATE error path's puts need not be the last ones. + * Another holder of a global-table reference, such as a concurrent reconnect + * of the same handle, can drop the last one through ksmbd_put_durable_fd(), + * which frees @fp without touching this table. Remove the id here, while + * the caller still holds its references. + * + * Every path that removes the id before the final put also clears + * @fp->volatile_id under ft->lock, so a valid id is still @fp's entry. + */ +void ksmbd_unpublish_reopened_fd(struct ksmbd_work *work, struct ksmbd_file *fp) +{ + struct ksmbd_file_table *ft = &work->sess->file_table; + + write_lock(&ft->lock); + if (has_file_id(fp->volatile_id)) { + idr_remove(ft->idr, fp->volatile_id); + fp->volatile_id = KSMBD_NO_FID; + } + write_unlock(&ft->lock); +} + int ksmbd_close_fd(struct ksmbd_work *work, u64 id) { struct ksmbd_file *fp; diff --git a/fs/smb/server/vfs_cache.h b/fs/smb/server/vfs_cache.h index 38ccf2957c174..3801872409193 100644 --- a/fs/smb/server/vfs_cache.h +++ b/fs/smb/server/vfs_cache.h @@ -158,6 +158,8 @@ static inline bool ksmbd_stream_fd(struct ksmbd_file *fp) int ksmbd_init_file_table(struct ksmbd_file_table *ft); void ksmbd_destroy_file_table(struct ksmbd_session *sess); int ksmbd_close_fd(struct ksmbd_work *work, u64 id); +void ksmbd_unpublish_reopened_fd(struct ksmbd_work *work, + struct ksmbd_file *fp); struct ksmbd_file *ksmbd_lookup_fd_fast(struct ksmbd_work *work, u64 id); struct ksmbd_file *ksmbd_lookup_foreign_fd(struct ksmbd_work *work, u64 id); struct ksmbd_file *ksmbd_lookup_fd_slow(struct ksmbd_work *work, u64 id, -- 2.53.0