user/sven/linux.git/kernel/user_namespace.c, branch v5.14.7

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2021-06-29T03:39:26Z

Pull user namespace rlimit handling update from Eric Biederman: "This is the work mainly by Alexey Gladkov to limit rlimits to the rlimits of the user that created a user namespace, and to allow users to have stricter limits on the resources created within a user namespace." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: cred: add missing return error code when set_cred_ucounts() failed ucounts: Silence warning in dec_rlimit_ucounts ucounts: Set ucount_max to the largest positive value the type can hold kselftests: Add test to check for rlimit changes in different user namespaces Reimplement RLIMIT_MEMLOCK on top of ucounts Reimplement RLIMIT_SIGPENDING on top of ucounts Reimplement RLIMIT_MSGQUEUE on top of ucounts Reimplement RLIMIT_NPROC on top of ucounts Use atomic_t for ucounts reference counting Add a reference to ucounts for each cred Increase size of ucounts to atomic_long_t

kernel/user_namespace.c: fix typos

2021-05-07T07:26:34Z

change 'verifing' to 'verifying' change 'certaint' to 'certain' change 'approprpiate' to 'appropriate' Link: https://lkml.kernel.org/r/20210317100129.12440-1-caoxiaofeng@yulong.com Signed-off-by: Xiaofeng Cao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ucounts: Set ucount_max to the largest positive value the type can hold

2021-04-30T19:14:03Z

The ns->ucount_max[] is signed long which is less than the rlimit size. We have to protect ucount_max[] from overflow and only use the largest value that we can hold. On 32bit using "long" instead of "unsigned long" to hold the counts has the downside that RLIMIT_MSGQUEUE and RLIMIT_MEMLOCK are limited to 2GiB instead of 4GiB. I don't think anyone cares but it should be mentioned in case someone does. The RLIMIT_NPROC and RLIMIT_SIGPENDING used atomic_t so their maximum hasn't changed. Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/1825a5dfa18bc5a570e79feb05e2bd07fd57e7e3.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman

Reimplement RLIMIT_MEMLOCK on top of ucounts

2021-04-30T19:14:02Z

The rlimit counter is tied to uid in the user_namespace. This allows rlimit values to be specified in userns even if they are already globally exceeded by the user. However, the value of the previous user_namespaces cannot be exceeded. Changelog v11: * Fix issue found by lkp robot. v8: * Fix issues found by lkp-tests project. v7: * Keep only ucounts for RLIMIT_MEMLOCK checks instead of struct cred. v6: * Fix bug in hugetlb_file_setup() detected by trinity. Reported-by: kernel test robot Reported-by: kernel test robot Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/970d50c70c71bfd4496e0e8d2a0a32feebebb350.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman

Reimplement RLIMIT_SIGPENDING on top of ucounts

2021-04-30T19:14:02Z

The rlimit counter is tied to uid in the user_namespace. This allows rlimit values to be specified in userns even if they are already globally exceeded by the user. However, the value of the previous user_namespaces cannot be exceeded. Changelog v11: * Revert most of changes to fix performance issues. v10: * Fix memory leak on get_ucounts failure. Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/df9d7764dddd50f28616b7840de74ec0f81711a8.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman

Reimplement RLIMIT_MSGQUEUE on top of ucounts

2021-04-30T19:14:01Z

The rlimit counter is tied to uid in the user_namespace. This allows rlimit values to be specified in userns even if they are already globally exceeded by the user. However, the value of the previous user_namespaces cannot be exceeded. Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/2531f42f7884bbfee56a978040b3e0d25cdf6cde.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman

Reimplement RLIMIT_NPROC on top of ucounts

2021-04-30T19:14:01Z

The rlimit counter is tied to uid in the user_namespace. This allows rlimit values to be specified in userns even if they are already globally exceeded by the user. However, the value of the previous user_namespaces cannot be exceeded. To illustrate the impact of rlimits, let's say there is a program that does not fork. Some service-A wants to run this program as user X in multiple containers. Since the program never fork the service wants to set RLIMIT_NPROC=1. service-A \- program (uid=1000, container1, rlimit_nproc=1) \- program (uid=1000, container2, rlimit_nproc=1) The service-A sets RLIMIT_NPROC=1 and runs the program in container1. When the service-A tries to run a program with RLIMIT_NPROC=1 in container2 it fails since user X already has one running process. We cannot use existing inc_ucounts / dec_ucounts because they do not allow us to exceed the maximum for the counter. Some rlimits can be overlimited by root or if the user has the appropriate capability. Changelog v11: * Change inc_rlimit_ucounts() which now returns top value of ucounts. * Drop inc_rlimit_ucounts_and_test() because the return code of inc_rlimit_ucounts() can be checked. Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/c5286a8aa16d2d698c222f7532f3d735c82bc6bc.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman

Add a reference to ucounts for each cred

2021-04-30T19:14:00Z

For RLIMIT_NPROC and some other rlimits the user_struct that holds the global limit is kept alive for the lifetime of a process by keeping it in struct cred. Adding a pointer to ucounts in the struct cred will allow to track RLIMIT_NPROC not only for user in the system, but for user in the user_namespace. Updating ucounts may require memory allocation which may fail. So, we cannot change cred.ucounts in the commit_creds() because this function cannot fail and it should always return 0. For this reason, we modify cred.ucounts before calling the commit_creds(). Changelog v6: * Fix null-ptr-deref in is_ucounts_overlimit() detected by trinity. This error was caused by the fact that cred_alloc_blank() left the ucounts pointer empty. Reported-by: kernel test robot Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/b37aaef28d8b9b0d757e07ba6dd27281bbe39259.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman

capabilities: require CAP_SETFCAP to map uid 0

2021-04-20T21:28:33Z

cap_setfcap is required to create file capabilities. Since commit 8db6c34f1dbc ("Introduce v3 namespaced file capabilities"), a process running as uid 0 but without cap_setfcap is able to work around this as follows: unshare a new user namespace which maps parent uid 0 into the child namespace. While this task will not have new capabilities against the parent namespace, there is a loophole due to the way namespaced file capabilities are represented as xattrs. File capabilities valid in userns 1 are distinguished from file capabilities valid in userns 2 by the kuid which underlies uid 0. Therefore the restricted root process can unshare a new self-mapping namespace, add a namespaced file capability onto a file, then use that file capability in the parent namespace. To prevent that, do not allow mapping parent uid 0 if the process which opened the uid_map file does not have CAP_SETFCAP, which is the capability for setting file capabilities. As a further wrinkle: a task can unshare its user namespace, then open its uid_map file itself, and map (only) its own uid. In this case we do not have the credential from before unshare, which was potentially more restricted. So, when creating a user namespace, we record whether the creator had CAP_SETFCAP. Then we can use that during map_write(). With this patch: 1. Unprivileged user can still unshare -Ur ubuntu@caps:~$ unshare -Ur root@caps:~# logout 2. Root user can still unshare -Ur ubuntu@caps:~$ sudo bash root@caps:/home/ubuntu# unshare -Ur root@caps:/home/ubuntu# logout 3. Root user without CAP_SETFCAP cannot unshare -Ur: root@caps:/home/ubuntu# /sbin/capsh --drop=cap_setfcap -- root@caps:/home/ubuntu# /sbin/setcap cap_setfcap=p /sbin/setcap unable to set CAP_SETFCAP effective capability: Operation not permitted root@caps:/home/ubuntu# unshare -Ur unshare: write failed /proc/self/uid_map: Operation not permitted Note: an alternative solution would be to allow uid 0 mappings by processes without CAP_SETFCAP, but to prevent such a namespace from writing any file capabilities. This approach can be seen at [1]. Background history: commit 95ebabde382 ("capabilities: Don't allow writing ambiguous v3 file capabilities") tried to fix the issue by preventing v3 fscaps to be written to disk when the root uid would map to the same uid in nested user namespaces. This led to regressions for various workloads. For example, see [2]. Ultimately this is a valid use-case we have to support meaning we had to revert this change in 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")"). Link: https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=2021-04-15/setfcap-nsfscaps-v4 [1] Link: https://github.com/containers/buildah/issues/3071 [2] Signed-off-by: Serge Hallyn Reviewed-by: Andrew G. Morgan Tested-by: Christian Brauner Reviewed-by: Christian Brauner Tested-by: Giuseppe Scrivano Cc: Eric Biederman Signed-off-by: Linus Torvalds

Merge tag 'fixes-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

2020-12-15T00:40:27Z

Pull misc fixes from Christian Brauner: "This contains several fixes which felt worth being combined into a single branch: - Use put_nsproxy() instead of open-coding it switch_task_namespaces() - Kirill's work to unify lifecycle management for all namespaces. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This work allows us to unify the type of the counters and reduces maintenance cost by moving the counter in one place and indicating that basic lifetime management is identical for all namespaces. - Peilin's fix adding three byte padding to Dmitry's PTRACE_GET_SYSCALL_INFO uapi struct to prevent an info leak. - Two smal patches to convert from the /* fall through */ comment annotation to the fallthrough keyword annotation which I had taken into my branch and into -next before df561f6688fe ("treewide: Use fallthrough pseudo-keyword") made it upstream which fixed this tree-wide. Since I didn't want to invalidate all testing for other commits I didn't rebase and kept them" * tag 'fixes-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: nsproxy: use put_nsproxy() in switch_task_namespaces() sys: Convert to the new fallthrough notation signal: Convert to the new fallthrough notation time: Use generic ns_common::count cgroup: Use generic ns_common::count mnt: Use generic ns_common::count user: Use generic ns_common::count pid: Use generic ns_common::count ipc: Use generic ns_common::count uts: Use generic ns_common::count net: Use generic ns_common::count ns: Add a common refcount into ns_common ptrace: Prevent kernel-infoleak in ptrace_get_syscall_info()