Commit 0889f44e authored by Alexey Gladkov's avatar Alexey Gladkov Committed by Eric W. Biederman
Browse files

ipc: Check permissions for checkpoint_restart sysctls at open time 

As Eric Biederman pointed out, it is possible not to use a custom
proc_handler and check permissions for every write, but to use a
.permission handler. That will allow the checkpoint_restart sysctls to
perform all of their permission checks at open time, and not need any
other special code.

Link: https://lore.kernel.org/lkml/87czib9g38.fsf@email.froward.int.ebiederm.org/


Fixes: 1f5c135e ("ipc: Store ipc sysctls in the ipc namespace")
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAlexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/65fa8459803830608da4610a39f33c76aa933eb9.1651584847.git.legion@kernel.org


Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent dd141a49

ipc/ipc_sysctl.c

+29 −28
Original line number Diff line number Diff line
@@ -68,25 +68,6 @@ static int proc_ipc_sem_dointvec(struct ctl_table *table, int write, 
	return ret;

}



#ifdef CONFIG_CHECKPOINT_RESTORE

static int proc_ipc_dointvec_minmax_checkpoint_restore(struct ctl_table *table,

		int write, void *buffer, size_t *lenp, loff_t *ppos)

{

	struct ipc_namespace *ns = table->extra1;

	struct ctl_table ipc_table;



	if (write && !checkpoint_restore_ns_capable(ns->user_ns))

		return -EPERM;



	memcpy(&ipc_table, table, sizeof(ipc_table));



	ipc_table.extra1 = SYSCTL_ZERO;

	ipc_table.extra2 = SYSCTL_INT_MAX;



	return proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);

}

#endif



int ipc_mni = IPCMNI;

int ipc_mni_shift = IPCMNI_SHIFT;

int ipc_min_cycle = RADIX_TREE_MAP_SIZE;
@@ -172,22 +153,28 @@ static struct ctl_table ipc_sysctls[] = { 
		.procname	= "sem_next_id",

		.data		= &init_ipc_ns.ids[IPC_SEM_IDS].next_id,

		.maxlen		= sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),

		.mode		= 0666,

		.proc_handler	= proc_ipc_dointvec_minmax_checkpoint_restore,

		.mode		= 0444,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= SYSCTL_ZERO,

		.extra2		= SYSCTL_INT_MAX,

	},

	{

		.procname	= "msg_next_id",

		.data		= &init_ipc_ns.ids[IPC_MSG_IDS].next_id,

		.maxlen		= sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),

		.mode		= 0666,

		.proc_handler	= proc_ipc_dointvec_minmax_checkpoint_restore,

		.mode		= 0444,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= SYSCTL_ZERO,

		.extra2		= SYSCTL_INT_MAX,

	},

	{

		.procname	= "shm_next_id",

		.data		= &init_ipc_ns.ids[IPC_SHM_IDS].next_id,

		.maxlen		= sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),

		.mode		= 0666,

		.proc_handler	= proc_ipc_dointvec_minmax_checkpoint_restore,

		.mode		= 0444,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= SYSCTL_ZERO,

		.extra2		= SYSCTL_INT_MAX,

	},

#endif

	{}
@@ -203,8 +190,25 @@ static int set_is_seen(struct ctl_table_set *set) 
	return &current->nsproxy->ipc_ns->ipc_set == set;

}



static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table)

{

	int mode = table->mode;



#ifdef CONFIG_CHECKPOINT_RESTORE

	struct ipc_namespace *ns = current->nsproxy->ipc_ns;



	if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) ||

	     (table->data == &ns->ids[IPC_MSG_IDS].next_id) ||

	     (table->data == &ns->ids[IPC_SHM_IDS].next_id)) &&

	    checkpoint_restore_ns_capable(ns->user_ns))

		mode = 0666;

#endif

	return mode;

}



static struct ctl_table_root set_root = {

	.lookup = set_lookup,

	.permissions = ipc_permissions,

};



bool setup_ipc_sysctls(struct ipc_namespace *ns)
@@ -244,15 +248,12 @@ bool setup_ipc_sysctls(struct ipc_namespace *ns) 
#ifdef CONFIG_CHECKPOINT_RESTORE

			} else if (tbl[i].data == &init_ipc_ns.ids[IPC_SEM_IDS].next_id) {

				tbl[i].data = &ns->ids[IPC_SEM_IDS].next_id;

				tbl[i].extra1 = ns;



			} else if (tbl[i].data == &init_ipc_ns.ids[IPC_MSG_IDS].next_id) {

				tbl[i].data = &ns->ids[IPC_MSG_IDS].next_id;

				tbl[i].extra1 = ns;



			} else if (tbl[i].data == &init_ipc_ns.ids[IPC_SHM_IDS].next_id) {

				tbl[i].data = &ns->ids[IPC_SHM_IDS].next_id;

				tbl[i].extra1 = ns;

#endif

			} else {

				tbl[i].data = NULL;