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

ucounts: Increase ucounts reference counter before the security hook

2021-08-23T21:13:04Z

We need to increment the ucounts reference counter befor security_prepare_creds() because this function may fail and abort_creds() will try to decrement this reference. [ 96.465056][ T8641] FAULT_INJECTION: forcing a failure. [ 96.465056][ T8641] name fail_page_alloc, interval 1, probability 0, space 0, times 0 [ 96.478453][ T8641] CPU: 1 PID: 8641 Comm: syz-executor668 Not tainted 5.14.0-rc6-syzkaller #0 [ 96.487215][ T8641] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 96.497254][ T8641] Call Trace: [ 96.500517][ T8641] dump_stack_lvl+0x1d3/0x29f [ 96.505758][ T8641] ? show_regs_print_info+0x12/0x12 [ 96.510944][ T8641] ? log_buf_vmcoreinfo_setup+0x498/0x498 [ 96.516652][ T8641] should_fail+0x384/0x4b0 [ 96.521141][ T8641] prepare_alloc_pages+0x1d1/0x5a0 [ 96.526236][ T8641] __alloc_pages+0x14d/0x5f0 [ 96.530808][ T8641] ? __rmqueue_pcplist+0x2030/0x2030 [ 96.536073][ T8641] ? lockdep_hardirqs_on_prepare+0x3e2/0x750 [ 96.542056][ T8641] ? alloc_pages+0x3f3/0x500 [ 96.546635][ T8641] allocate_slab+0xf1/0x540 [ 96.551120][ T8641] ___slab_alloc+0x1cf/0x350 [ 96.555689][ T8641] ? kzalloc+0x1d/0x30 [ 96.559740][ T8641] __kmalloc+0x2e7/0x390 [ 96.563980][ T8641] ? kzalloc+0x1d/0x30 [ 96.568029][ T8641] kzalloc+0x1d/0x30 [ 96.571903][ T8641] security_prepare_creds+0x46/0x220 [ 96.577174][ T8641] prepare_creds+0x411/0x640 [ 96.581747][ T8641] __sys_setfsuid+0xe2/0x3a0 [ 96.586333][ T8641] do_syscall_64+0x3d/0xb0 [ 96.590739][ T8641] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 96.596611][ T8641] RIP: 0033:0x445a69 [ 96.600483][ T8641] Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 [ 96.620152][ T8641] RSP: 002b:00007f1054173318 EFLAGS: 00000246 ORIG_RAX: 000000000000007a [ 96.628543][ T8641] RAX: ffffffffffffffda RBX: 00000000004ca4c8 RCX: 0000000000445a69 [ 96.636600][ T8641] RDX: 0000000000000010 RSI: 00007f10541732f0 RDI: 0000000000000000 [ 96.644550][ T8641] RBP: 00000000004ca4c0 R08: 0000000000000001 R09: 0000000000000000 [ 96.652500][ T8641] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004ca4cc [ 96.660631][ T8641] R13: 00007fffffe0b62f R14: 00007f1054173400 R15: 0000000000022000 Fixes: 905ae01c4ae2 ("Add a reference to ucounts for each cred") Reported-by: syzbot+01985d7909f9468f013c@syzkaller.appspotmail.com Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/97433b1742c3331f02ad92de5a4f07d673c90613.1629735352.git.legion@kernel.org Signed-off-by: Eric W. Biederman

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

cred: add missing return error code when set_cred_ucounts() failed

2021-05-28T18:12:52Z

If set_cred_ucounts() failed, we need return the error code. Fixes: 905ae01c4ae2 ("Add a reference to ucounts for each cred") Reported-by: Hulk Robot Signed-off-by: Yang Yingliang Link: https://lkml.kernel.org/r/20210526143805.2549649-1-yangyingliang@huawei.com Reviewed-by: Alexey Gladkov Signed-off-by: Eric W. Biederman

kernel/cred.c: make init_groups static

2021-05-07T02:24:11Z

init_groups is declared in both cred.h and init_task.h, but it is not actually referenced anywhere outside of cred.c where it is defined. So make it static and remove the declarations. Link: https://lkml.kernel.org/r/20210310220102.2484201-1-linux@rasmusvillemoes.dk Signed-off-by: Rasmus Villemoes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

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

exec: Teach prepare_exec_creds how exec treats uids & gids

2020-05-20T19:44:21Z

It is almost possible to use the result of prepare_exec_creds with no modifications during exec. Update prepare_exec_creds to initialize the suid and the fsuid to the euid, and the sgid and the fsgid to the egid. This is all that is needed to handle the common case of exec when nothing special like a setuid exec is happening. That this preserves the existing behavior of exec can be verified by examing bprm_fill_uid and cap_bprm_set_creds. This change makes it clear that the later parts of exec that update bprm->cred are just need to handle special cases such as setuid exec and change of domains. Link: https://lkml.kernel.org/r/871rng22dm.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds Reviewed-by: Kees Cook Signed-off-by: "Eric W. Biederman"

kernel: doc: remove outdated comment cred.c

2020-03-25T15:04:01Z

This removes an outdated comment in prepare_kernel_cred. There is no "cred_replace_mutex" any more, so the comment must go away. Signed-off-by: Bernd Edlinger Reviewed-by: Kees Cook Signed-off-by: Eric W. Biederman

Merge branch 'dhowells' (patches from DavidH)

2020-01-14T17:56:31Z

Merge misc fixes from David Howells. Two afs fixes and a key refcounting fix. * dhowells: afs: Fix afs_lookup() to not clobber the version on a new dentry afs: Fix use-after-loss-of-ref keys: Fix request_key() cache

keys: Fix request_key() cache

2020-01-14T17:40:06Z

When the key cached by request_key() and co. is cleaned up on exit(), the code looks in the wrong task_struct, and so clears the wrong cache. This leads to anomalies in key refcounting when doing, say, a kernel build on an afs volume, that then trigger kasan to report a use-after-free when the key is viewed in /proc/keys. Fix this by making exit_creds() look in the passed-in task_struct rather than in current (the task_struct cleanup code is deferred by RCU and potentially run in another task). Fixes: 7743c48e54ee ("keys: Cache result of request_key*() temporarily in task_struct") Signed-off-by: David Howells Signed-off-by: Linus Torvalds