The patch titled Subject: pidns: limit the nesting depth of pid namespaces has been removed from the -mm tree. Its filename was pidns-limit-the-nesting-depth-of-pid-namespaces.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Andrew Vagin <avagin@xxxxxxxxxx> Subject: pidns: limit the nesting depth of pid namespaces 'struct pid' is a "variable sized struct" - a header with an array of upids at the end. The size of the array depends on a level (depth) of pid namespaces. Now a level of pidns is not limited, so 'struct pid' can be more than one page. Looks reasonable, that it should be less than a page. MAX_PIS_NS_LEVEL is not calculated from PAGE_SIZE, because in this case it depends on architectures, config options and it will be reduced, if someone adds a new fields in struct pid or struct upid. I suggest to set MAX_PIS_NS_LEVEL = 32, because it saves ability to expand "struct pid" and it's more than enough for all known for me use-cases. When someone finds a reasonable use case, we can add a config option or a sysctl parameter. In addition it will reduce the effect of another problem, when we have many nested namespaces and the oldest one starts dying. zap_pid_ns_processe will be called for each namespace and find_vpid will be called for each process in a namespace. find_vpid will be called minimum max_level^2 / 2 times. The reason of that is that when we found a bit in pidmap, we can't determine this pidns is top for this process or it isn't. vpid is a heavy operation, so a fork bomb, which create many nested namespace, can make a system inaccessible for a long time. For example my system becomes inaccessible for a few minutes with 4000 processes. [akpm@xxxxxxxxxxxxxxxxxxxx: return -EINVAL in response to excessive nesting, not -ENOMEM] Signed-off-by: Andrew Vagin <avagin@xxxxxxxxxx> Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/pid_namespace.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff -puN kernel/pid_namespace.c~pidns-limit-the-nesting-depth-of-pid-namespaces kernel/pid_namespace.c --- a/kernel/pid_namespace.c~pidns-limit-the-nesting-depth-of-pid-namespaces +++ a/kernel/pid_namespace.c @@ -71,12 +71,22 @@ err_alloc: return NULL; } +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ +#define MAX_PID_NS_LEVEL 32 + static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns) { struct pid_namespace *ns; unsigned int level = parent_pid_ns->level + 1; - int i, err = -ENOMEM; + int i; + int err; + + if (level > MAX_PID_NS_LEVEL) { + err = -EINVAL; + goto out; + } + err = -ENOMEM; ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); if (ns == NULL) goto out; _ Patches currently in -mm which might be from avagin@xxxxxxxxxx are linux-next.patch proc-dont-show-nonexistent-capabilities.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html