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ksmbd: fix app-instance durable supersede session UAF

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ksmbd_close_fd_app_instance_id() looks up a prior durable handle by
AppInstanceId and closes it through opinfo->sess->file_table. This is
unsafe after the original session has been torn down. session_fd_check()
preserves reconnectable durable handles in the global table and clears
opinfo->conn/fp->conn, but opinfo->sess can still point to the freed
ksmbd_session.

Use opinfo->conn as the orphan sentinel, but make the check reliable by
serializing it with session_fd_check(). That path clears opinfo->conn
under fp->f_ci->m_lock, so hold the same lock while testing opinfo->conn
and while dereferencing opinfo->sess->file_table. Also avoid closing
through the session file table if the volatile id has already been
unpublished by session teardown.

Durable reconnect must keep the two fields consistent. Rebinding only
opinfo->conn leaves opinfo->sess pointing at the old freed session, so
a later app-instance supersede can pass the conn check and write-lock the
freed session's file table. Clear opinfo->sess when preserving a durable
handle during session teardown, and set it to the reconnecting session
when opinfo->conn is rebound in ksmbd_reopen_durable_fd().

Fixes: 16c3064970 ("ksmbd: handle durable v2 app instance id")
Reported-by: Gil Portnoy <dddhkts1@gmail.com>
Co-developed-by: Gil Portnoy <dddhkts1@gmail.com>
Signed-off-by: Gil Portnoy <dddhkts1@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Namjae Jeon 2026-06-28 08:56:09 +09:00 committed by Steve French
parent 5138c84dbb
commit f363a0fb13
1 changed files with 13 additions and 6 deletions
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19
fs/smb/server/vfs_cache.c
View File

@ -853,19 +853,24 @@ int ksmbd_close_fd_app_instance_id(char *app_instance_id)
return 0;
opinfo = opinfo_get(fp);
if (!opinfo || !opinfo->sess)
if (!opinfo)
goto out;
down_read(&fp->f_ci->m_lock);
if (!opinfo->conn) {
up_read(&fp->f_ci->m_lock);
goto out;
}
ft = &opinfo->sess->file_table;
write_lock(&ft->lock);
if (fp->f_state == FP_INITED) {
if (has_file_id(fp->volatile_id)) {
idr_remove(ft->idr, fp->volatile_id);
fp->volatile_id = KSMBD_NO_FID;
}
if (fp->f_state == FP_INITED && has_file_id(fp->volatile_id)) {
idr_remove(ft->idr, fp->volatile_id);
fp->volatile_id = KSMBD_NO_FID;
n_to_drop = ksmbd_mark_fp_closed(fp);
}
write_unlock(&ft->lock);
up_read(&fp->f_ci->m_lock);
opinfo_put(opinfo);
opinfo = NULL;
@ -1562,6 +1567,7 @@ static bool session_fd_check(struct ksmbd_tree_connect *tcon,
continue;
ksmbd_conn_put(op->conn);
op->conn = NULL;
op->sess = NULL;
}
up_write(&ci->m_lock);
@ -1717,6 +1723,7 @@ int ksmbd_reopen_durable_fd(struct ksmbd_work *work, struct ksmbd_file *fp)
if (op->conn)
continue;
op->conn = ksmbd_conn_get(fp->conn);
op->sess = work->sess;
}
up_write(&ci->m_lock);