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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ Fixes: 1f5c135ee509 ("ipc: Store ipc sysctls in the ipc namespace") Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx> --- ipc/ipc_sysctl.c | 57 ++++++++++++++++++++++++------------------------ 1 file changed, 29 insertions(+), 28 deletions(-) diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c index eb7ba8e0a355..5a58598d48c8 100644 --- a/ipc/ipc_sysctl.c +++ b/ipc/ipc_sysctl.c @@ -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 ¤t->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; -- 2.33.3
