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ipc: Check permissions for checkpoint_restart sysctls at open time

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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: 1f5c135ee5 ("ipc: Store ipc sysctls in the ipc namespace")
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/65fa8459803830608da4610a39f33c76aa933eb9.1651584847.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Alexey Gladkov 2022-05-03 15:39:56 +02:00 committed by Eric W. Biederman
parent dd141a4955
commit 0889f44e28
1 changed files with 29 additions and 28 deletions
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57
ipc/ipc_sysctl.c
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@ -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;