From 5ddf994fa22f78ae3742d72520a8c3e8521d96cd Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Mon, 23 Aug 2021 11:12:17 -0500 Subject: [PATCH 1/2] ucounts: Fix regression preventing increasing of rlimits in init_user_ns "Ma, XinjianX" reported: > When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests > in kselftest failed with following message. > > # selftests: mqueue: mq_perf_tests > # > # Initial system state: > # Using queue path: /mq_perf_tests > # RLIMIT_MSGQUEUE(soft): 819200 > # RLIMIT_MSGQUEUE(hard): 819200 > # Maximum Message Size: 8192 > # Maximum Queue Size: 10 > # Nice value: 0 > # > # Adjusted system state for testing: > # RLIMIT_MSGQUEUE(soft): (unlimited) > # RLIMIT_MSGQUEUE(hard): (unlimited) > # Maximum Message Size: 16777216 > # Maximum Queue Size: 65530 > # Nice value: -20 > # Continuous mode: (disabled) > # CPUs to pin: 3 > # ./mq_perf_tests: mq_open() at 296: Too many open files > not ok 2 selftests: mqueue: mq_perf_tests # exit=1 > ``` > > Test env: > rootfs: debian-10 > gcc version: 9 After investigation the problem turned out to be that ucount_max for the rlimits in init_user_ns was being set to the initial rlimit value. The practical problem is that ucount_max provides a limit that applications inside the user namespace can not exceed. Which means in practice that rlimits that have been converted to use the ucount infrastructure were not able to exceend their initial rlimits. Solve this by setting the relevant values of ucount_max to RLIM_INIFINITY. A limit in init_user_ns is pointless so the code should allow the values to grow as large as possible without riscking an underflow or an overflow. As the ltp test case was a bit of a pain I have reproduced the rlimit failure and tested the fix with the following little C program: > #include > #include > #include > #include > #include > #include > #include > #include > #include > #include > #include > > int main(int argc, char **argv) > { > struct mq_attr mq_attr; > struct rlimit rlim; > mqd_t mqd; > int ret; > > ret = getrlimit(RLIMIT_MSGQUEUE, &rlim); > if (ret != 0) { > fprintf(stderr, "getrlimit(RLIMIT_MSGQUEUE) failed: %s\n", strerror(errno)); > exit(EXIT_FAILURE); > } > printf("RLIMIT_MSGQUEUE %lu %lu\n", > rlim.rlim_cur, rlim.rlim_max); > rlim.rlim_cur = RLIM_INFINITY; > rlim.rlim_max = RLIM_INFINITY; > ret = setrlimit(RLIMIT_MSGQUEUE, &rlim); > if (ret != 0) { > fprintf(stderr, "setrlimit(RLIMIT_MSGQUEUE, RLIM_INFINITY) failed: %s\n", strerror(errno)); > exit(EXIT_FAILURE); > } > > memset(&mq_attr, 0, sizeof(struct mq_attr)); > mq_attr.mq_maxmsg = 65536 - 1; > mq_attr.mq_msgsize = 16*1024*1024 - 1; > > mqd = mq_open("/mq_rlimit_test", O_RDONLY|O_CREAT, 0600, &mq_attr); > if (mqd == (mqd_t)-1) { > fprintf(stderr, "mq_open failed: %s\n", strerror(errno)); > exit(EXIT_FAILURE); > } > ret = mq_close(mqd); > if (ret) { > fprintf(stderr, "mq_close failed; %s\n", strerror(errno)); > exit(EXIT_FAILURE); > } > > return EXIT_SUCCESS; > } Fixes: 6e52a9f0532f ("Reimplement RLIMIT_MSGQUEUE on top of ucounts") Fixes: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts") Fixes: d64696905554 ("Reimplement RLIMIT_SIGPENDING on top of ucounts") Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts") Reported-by: kernel test robot lkp@intel.com Acked-by: Alexey Gladkov Link: https://lkml.kernel.org/r/87eeajswfc.fsf_-_@disp2133 Signed-off-by: "Eric W. Biederman" --- kernel/fork.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index bc94b2cc5995..44f4c2d83763 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -828,10 +828,10 @@ void __init fork_init(void) for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++) init_user_ns.ucount_max[i] = max_threads/2; - set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, task_rlimit(&init_task, RLIMIT_NPROC)); - set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE)); - set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, task_rlimit(&init_task, RLIMIT_SIGPENDING)); - set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, task_rlimit(&init_task, RLIMIT_MEMLOCK)); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY); #ifdef CONFIG_VMAP_STACK cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", From bbb6d0f3e1feb43d663af089c7dedb23be6a04fb Mon Sep 17 00:00:00 2001 From: Alexey Gladkov Date: Mon, 23 Aug 2021 18:16:33 +0200 Subject: [PATCH 2/2] ucounts: Increase ucounts reference counter before the security hook 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 --- kernel/cred.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/cred.c b/kernel/cred.c index e6fd2b3fc31f..f784e08c2fbd 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -286,13 +286,13 @@ struct cred *prepare_creds(void) new->security = NULL; #endif - if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) - goto error; - new->ucounts = get_ucounts(new->ucounts); if (!new->ucounts) goto error; + if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + goto error; + validate_creds(new); return new; @@ -753,13 +753,13 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon) #ifdef CONFIG_SECURITY new->security = NULL; #endif - if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) - goto error; - new->ucounts = get_ucounts(new->ucounts); if (!new->ucounts) goto error; + if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + goto error; + put_cred(old); validate_creds(new); return new;