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cec16052d5
This patch enables the "/proc/sys/net/unix/max_dgram_qlen" sysctl to be exposed to non-init user namespaces. max_dgram_qlen is used as the default "sk_max_ack_backlog" value for when a unix socket is created. Currently, when a networking namespace is initialized, its unix sysctls are exposed only if the user namespace that "owns" it is the init user namespace. If there is an non-init user namespace that "owns" a networking namespace (for example, in the case after we call clone() with both CLONE_NEWUSER and CLONE_NEWNET set), the sysctls are hidden from view and not configurable. Exposing the unix sysctl is safe because any changes made to it will be limited in scope to the networking namespace the non-init user namespace "owns" and has privileges over (changes won't affect any other net namespace). There is also no possibility of a non-privileged user namespace messing up the net namespace sysctls it shares with its parent user namespace. When a new user namespace is created without unsharing the network namespace (eg calling clone() with CLONE_NEWUSER), the new user namespace shares its parent's network namespace. Write access is protected by the mode set in the sysctl's ctl_table (and enforced by procfs). Here in the case of "max_dgram_qlen", 0644 is set; only the user owner has write access. v1 -> v2: * Add more detail to commit message, specify the "/proc/sys/net/unix/max_dgram_qlen" sysctl in commit message. Signed-off-by: Joanne Koong <joannekoong@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
54 lines
1022 B
C
54 lines
1022 B
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* NET4: Sysctl interface to net af_unix subsystem.
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*
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* Authors: Mike Shaver.
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*/
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/sysctl.h>
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#include <net/af_unix.h>
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static struct ctl_table unix_table[] = {
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{
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.procname = "max_dgram_qlen",
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.data = &init_net.unx.sysctl_max_dgram_qlen,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{ }
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};
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int __net_init unix_sysctl_register(struct net *net)
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{
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struct ctl_table *table;
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table = kmemdup(unix_table, sizeof(unix_table), GFP_KERNEL);
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if (table == NULL)
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goto err_alloc;
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table[0].data = &net->unx.sysctl_max_dgram_qlen;
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net->unx.ctl = register_net_sysctl(net, "net/unix", table);
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if (net->unx.ctl == NULL)
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goto err_reg;
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return 0;
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err_reg:
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kfree(table);
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err_alloc:
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return -ENOMEM;
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}
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void unix_sysctl_unregister(struct net *net)
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{
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struct ctl_table *table;
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table = net->unx.ctl->ctl_table_arg;
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unregister_net_sysctl_table(net->unx.ctl);
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kfree(table);
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}
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