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415e3d3e90
The commit referenced in the Fixes tag incorrectly accounted the number
of in-flight fds over a unix domain socket to the original opener
of the file-descriptor. This allows another process to arbitrary
deplete the original file-openers resource limit for the maximum of
open files. Instead the sending processes and its struct cred should
be credited.
To do so, we add a reference counted struct user_struct pointer to the
scm_fp_list and use it to account for the number of inflight unix fds.
Fixes: 712f4aad40 ("unix: properly account for FDs passed over unix sockets")
Reported-by: David Herrmann <dh.herrmann@gmail.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
143 lines
3.4 KiB
C
143 lines
3.4 KiB
C
#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/security.h>
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#include <linux/pid.h>
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#include <linux/nsproxy.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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struct scm_fp_list {
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short count;
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short max;
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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);
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void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm);
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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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#ifdef CONFIG_SECURITY_NETWORK
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static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
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{
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char *secdata;
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u32 seclen;
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int err;
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if (test_bit(SOCK_PASSSEC, &sock->flags)) {
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err = security_secid_to_secctx(scm->secid, &secdata, &seclen);
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if (!err) {
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put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, seclen, secdata);
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security_release_secctx(secdata, seclen);
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}
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}
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}
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#else
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static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
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{ }
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#endif /* CONFIG_SECURITY_NETWORK */
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static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
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struct scm_cookie *scm, int flags)
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{
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if (!msg->msg_control) {
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if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp)
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msg->msg_flags |= MSG_CTRUNC;
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scm_destroy(scm);
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return;
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}
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if (test_bit(SOCK_PASSCRED, &sock->flags)) {
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struct user_namespace *current_ns = current_user_ns();
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struct ucred ucreds = {
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.pid = scm->creds.pid,
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.uid = from_kuid_munged(current_ns, scm->creds.uid),
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.gid = from_kgid_munged(current_ns, scm->creds.gid),
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};
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put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds);
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}
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scm_destroy_cred(scm);
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scm_passec(sock, msg, scm);
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if (!scm->fp)
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return;
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scm_detach_fds(msg, scm);
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}
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#endif /* __LINUX_NET_SCM_H */
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