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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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fd8756fa14
Right now if some LSM such as Smack denies an AF_UNIX socket peer to receive an SCM_RIGHTS fd, the SCM_RIGHTS fd array will be cut short at that point, and MSG_CTRUNC is set on return of recvmsg(). This is highly problematic behaviour, because it leaves the receiver wondering what happened. As per man page MSG_CTRUNC is supposed to indicate that the control buffer was sized too short, but suddenly a permission error might result in the exact same flag being set. Moreover, the receiver has no chance to determine how many fds got originally sent and how many were suppressed.[1] Add a SO_RIGHTS_NOTRUNC option to UNIX sockets to enable more useful handling of LSM denials when receiving SCM_RIGHTS messages: instead of truncating the message at the first blocked fd, keep every fd slot and store the LSM errno in the blocked slot. The socket option is inherited by the child accept() socket if set on the listen() socket. [1]: https://github.com/uapi-group/kernel-features#useful-handling-of-lsm-denials-on-scm_rights Reviewed-by: Christian Brauner (Amutable) <brauner@kernel.org> Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl> Link: https://patch.msgid.link/20260813162818.149248-4-jkoolstra@xs4all.nl Signed-off-by: Jakub Kicinski <kuba@kernel.org>
115 lines
2.8 KiB
C
115 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_NET_SCM_H
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#define __LINUX_NET_SCM_H
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#include <linux/limits.h>
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#include <linux/net.h>
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#include <linux/cred.h>
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#include <linux/file.h>
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#include <linux/security.h>
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#include <linux/pid.h>
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#include <linux/nsproxy.h>
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#include <linux/sched/signal.h>
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#include <net/compat.h>
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/* Well, we should have at least one descriptor open
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* to accept passed FDs 8)
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*/
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#define SCM_MAX_FD 253
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struct scm_creds {
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u32 pid;
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kuid_t uid;
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kgid_t gid;
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};
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#ifdef CONFIG_UNIX
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struct unix_edge;
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#endif
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struct scm_fp_list {
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short count;
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short count_unix;
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short max;
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#ifdef CONFIG_UNIX
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bool inflight;
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bool dead;
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struct list_head vertices;
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struct unix_edge *edges;
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#endif
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struct user_struct *user;
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struct file *fp[SCM_MAX_FD];
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};
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struct scm_cookie {
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struct pid *pid; /* Skb credentials */
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struct scm_fp_list *fp; /* Passed files */
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struct scm_creds creds; /* Skb credentials */
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#ifdef CONFIG_SECURITY_NETWORK
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u32 secid; /* Passed security ID */
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#endif
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};
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void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm, bool notrunc);
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void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm, bool notrunc);
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int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm);
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void __scm_destroy(struct scm_cookie *scm);
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struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl);
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#ifdef CONFIG_SECURITY_NETWORK
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static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
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{
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security_socket_getpeersec_dgram(sock, NULL, &scm->secid);
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}
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#else
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static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
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{ }
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#endif /* CONFIG_SECURITY_NETWORK */
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static __inline__ void scm_set_cred(struct scm_cookie *scm,
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struct pid *pid, kuid_t uid, kgid_t gid)
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{
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scm->pid = get_pid(pid);
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scm->creds.pid = pid_vnr(pid);
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scm->creds.uid = uid;
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scm->creds.gid = gid;
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}
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static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
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{
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put_pid(scm->pid);
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scm->pid = NULL;
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}
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static __inline__ void scm_destroy(struct scm_cookie *scm)
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{
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scm_destroy_cred(scm);
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if (scm->fp)
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__scm_destroy(scm);
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}
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static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
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struct scm_cookie *scm, bool forcecreds)
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{
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memset(scm, 0, sizeof(*scm));
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scm->creds.uid = INVALID_UID;
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scm->creds.gid = INVALID_GID;
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if (forcecreds)
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scm_set_cred(scm, task_tgid(current), current_uid(), current_gid());
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unix_get_peersec_dgram(sock, scm);
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if (msg->msg_controllen <= 0)
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return 0;
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return __scm_send(sock, msg, scm);
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}
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void scm_recv(struct socket *sock, struct msghdr *msg,
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struct scm_cookie *scm, int flags);
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void scm_recv_unix(struct socket *sock, struct msghdr *msg,
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struct scm_cookie *scm, int flags);
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int scm_recv_one_fd(struct file *f, int __user *ufd, unsigned int flags,
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bool notrunc);
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#endif /* __LINUX_NET_SCM_H */
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