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net: split out functions related to registering inflight socket files
We need this functionality for the io_uring file registration, but we cannot rely on it since CONFIG_UNIX can be modular. Move the helpers to a separate file, that's always builtin to the kernel if CONFIG_UNIX is m/y. No functional changes in this patch, just moving code around. Reviewed-by: Hannes Reinecke <hare@suse.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Jens Axboe
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Feb 28, 2019
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,151 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
| #include <linux/module.h> | ||
| #include <linux/kernel.h> | ||
| #include <linux/string.h> | ||
| #include <linux/socket.h> | ||
| #include <linux/net.h> | ||
| #include <linux/fs.h> | ||
| #include <net/af_unix.h> | ||
| #include <net/scm.h> | ||
| #include <linux/init.h> | ||
|
|
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| #include "scm.h" | ||
|
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| unsigned int unix_tot_inflight; | ||
| EXPORT_SYMBOL(unix_tot_inflight); | ||
|
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| LIST_HEAD(gc_inflight_list); | ||
| EXPORT_SYMBOL(gc_inflight_list); | ||
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| DEFINE_SPINLOCK(unix_gc_lock); | ||
| EXPORT_SYMBOL(unix_gc_lock); | ||
|
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| struct sock *unix_get_socket(struct file *filp) | ||
| { | ||
| struct sock *u_sock = NULL; | ||
| struct inode *inode = file_inode(filp); | ||
|
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||
| /* Socket ? */ | ||
| if (S_ISSOCK(inode->i_mode) && !(filp->f_mode & FMODE_PATH)) { | ||
| struct socket *sock = SOCKET_I(inode); | ||
| struct sock *s = sock->sk; | ||
|
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||
| /* PF_UNIX ? */ | ||
| if (s && sock->ops && sock->ops->family == PF_UNIX) | ||
| u_sock = s; | ||
| } else { | ||
| /* Could be an io_uring instance */ | ||
| u_sock = io_uring_get_socket(filp); | ||
| } | ||
| return u_sock; | ||
| } | ||
| EXPORT_SYMBOL(unix_get_socket); | ||
|
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||
| /* Keep the number of times in flight count for the file | ||
| * descriptor if it is for an AF_UNIX socket. | ||
| */ | ||
| void unix_inflight(struct user_struct *user, struct file *fp) | ||
| { | ||
| struct sock *s = unix_get_socket(fp); | ||
|
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| spin_lock(&unix_gc_lock); | ||
|
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| if (s) { | ||
| struct unix_sock *u = unix_sk(s); | ||
|
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||
| if (atomic_long_inc_return(&u->inflight) == 1) { | ||
| BUG_ON(!list_empty(&u->link)); | ||
| list_add_tail(&u->link, &gc_inflight_list); | ||
| } else { | ||
| BUG_ON(list_empty(&u->link)); | ||
| } | ||
| unix_tot_inflight++; | ||
| } | ||
| user->unix_inflight++; | ||
| spin_unlock(&unix_gc_lock); | ||
| } | ||
|
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| void unix_notinflight(struct user_struct *user, struct file *fp) | ||
| { | ||
| struct sock *s = unix_get_socket(fp); | ||
|
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| spin_lock(&unix_gc_lock); | ||
|
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| if (s) { | ||
| struct unix_sock *u = unix_sk(s); | ||
|
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| BUG_ON(!atomic_long_read(&u->inflight)); | ||
| BUG_ON(list_empty(&u->link)); | ||
|
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| if (atomic_long_dec_and_test(&u->inflight)) | ||
| list_del_init(&u->link); | ||
| unix_tot_inflight--; | ||
| } | ||
| user->unix_inflight--; | ||
| spin_unlock(&unix_gc_lock); | ||
| } | ||
|
|
||
| /* | ||
| * The "user->unix_inflight" variable is protected by the garbage | ||
| * collection lock, and we just read it locklessly here. If you go | ||
| * over the limit, there might be a tiny race in actually noticing | ||
| * it across threads. Tough. | ||
| */ | ||
| static inline bool too_many_unix_fds(struct task_struct *p) | ||
| { | ||
| struct user_struct *user = current_user(); | ||
|
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||
| if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE))) | ||
| return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN); | ||
| return false; | ||
| } | ||
|
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| int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb) | ||
| { | ||
| int i; | ||
|
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||
| if (too_many_unix_fds(current)) | ||
| return -ETOOMANYREFS; | ||
|
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||
| /* | ||
| * Need to duplicate file references for the sake of garbage | ||
| * collection. Otherwise a socket in the fps might become a | ||
| * candidate for GC while the skb is not yet queued. | ||
| */ | ||
| UNIXCB(skb).fp = scm_fp_dup(scm->fp); | ||
| if (!UNIXCB(skb).fp) | ||
| return -ENOMEM; | ||
|
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| for (i = scm->fp->count - 1; i >= 0; i--) | ||
| unix_inflight(scm->fp->user, scm->fp->fp[i]); | ||
| return 0; | ||
| } | ||
| EXPORT_SYMBOL(unix_attach_fds); | ||
|
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| void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb) | ||
| { | ||
| int i; | ||
|
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| scm->fp = UNIXCB(skb).fp; | ||
| UNIXCB(skb).fp = NULL; | ||
|
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| for (i = scm->fp->count-1; i >= 0; i--) | ||
| unix_notinflight(scm->fp->user, scm->fp->fp[i]); | ||
| } | ||
| EXPORT_SYMBOL(unix_detach_fds); | ||
|
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| void unix_destruct_scm(struct sk_buff *skb) | ||
| { | ||
| struct scm_cookie scm; | ||
|
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| memset(&scm, 0, sizeof(scm)); | ||
| scm.pid = UNIXCB(skb).pid; | ||
| if (UNIXCB(skb).fp) | ||
| unix_detach_fds(&scm, skb); | ||
|
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| /* Alas, it calls VFS */ | ||
| /* So fscking what? fput() had been SMP-safe since the last Summer */ | ||
| scm_destroy(&scm); | ||
| sock_wfree(skb); | ||
| } | ||
| EXPORT_SYMBOL(unix_destruct_scm); |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,10 @@ | ||
| #ifndef NET_UNIX_SCM_H | ||
| #define NET_UNIX_SCM_H | ||
|
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| extern struct list_head gc_inflight_list; | ||
| extern spinlock_t unix_gc_lock; | ||
|
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| int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb); | ||
| void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb); | ||
|
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||
| #endif |