linux/kernel/events, branch v6.14

perf/core: Fix perf_pmu_register() vs. perf_init_event()

2025-03-01T18:38:42Z

There is a fairly obvious race between perf_init_event() doing idr_find() and perf_pmu_register() doing idr_alloc() with an incompletely initialized PMU pointer. Avoid by doing idr_alloc() on a NULL pointer to register the id, and swizzling the real struct pmu pointer at the end using idr_replace(). Also making sure to not set struct pmu members after publishing the struct pmu, duh. [ introduce idr_cmpxchg() in order to better handle the idr_replace() error case -- if it were to return an unexpected pointer, it will already have replaced the value and there is no going back. ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20241104135517.858805880@infradead.org

perf/core: Fix pmus_lock vs. pmus_srcu ordering

2025-03-01T18:38:42Z

Commit a63fbed776c7 ("perf/tracing/cpuhotplug: Fix locking order") placed pmus_lock inside pmus_srcu, this makes perf_pmu_unregister() trip lockdep. Move the locking about such that only pmu_idr and pmus (list) are modified while holding pmus_lock. This avoids doing synchronize_srcu() while holding pmus_lock and all is well again. Fixes: a63fbed776c7 ("perf/tracing/cpuhotplug: Fix locking order") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20241104135517.679556858@infradead.org

uprobes: Remove too strict lockdep_assert() condition in hprobe_expire()

2025-02-25T22:36:19Z

hprobe_expire() is used to atomically switch pending uretprobe instance (struct return_instance) from being SRCU protected to be refcounted. This can be done from background timer thread, or synchronously within current thread when task is forked. In the former case, return_instance has to be protected through RCU read lock, and that's what hprobe_expire() used to check with lockdep_assert(rcu_read_lock_held()). But in the latter case (hprobe_expire() called from dup_utask()) there is no RCU lock being held, and it's both unnecessary and incovenient. Inconvenient due to the intervening memory allocations inside dup_return_instance()'s loop. Unnecessary because dup_utask() is called synchronously in current thread, and no uretprobe can run at that point, so return_instance can't be freed either. So drop rcu_read_lock_held() condition, and expand corresponding comment to explain necessary lifetime guarantees. lockdep_assert()-detected issue is a false positive. Fixes: dd1a7567784e ("uprobes: SRCU-protect uretprobe lifetime (with timeout)") Reported-by: Breno Leitao Signed-off-by: Andrii Nakryiko Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20250225223214.2970740-1-andrii@kernel.org

perf/core: Fix low freq setting via IOC_PERIOD

2025-02-25T13:54:14Z

A low attr::freq value cannot be set via IOC_PERIOD on some platforms. The perf_event_check_period() introduced in: 81ec3f3c4c4d ("perf/x86: Add check_period PMU callback") was intended to check the period, rather than the frequency. A low frequency may be mistakenly rejected by limit_period(). Fix it. Fixes: 81ec3f3c4c4d ("perf/x86: Add check_period PMU callback") Signed-off-by: Kan Liang Signed-off-by: Ingo Molnar Reviewed-by: Ravi Bangoria Cc: Peter Zijlstra Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250117151913.3043942-2-kan.liang@linux.intel.com Closes: https://lore.kernel.org/lkml/20250115154949.3147-1-ravi.bangoria@amd.com/

uprobes: Reject the shared zeropage in uprobe_write_opcode()

2025-02-24T19:37:45Z

We triggered the following crash in syzkaller tests: BUG: Bad page state in process syz.7.38 pfn:1eff3 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1eff3 flags: 0x3fffff00004004(referenced|reserved|node=0|zone=1|lastcpupid=0x1fffff) raw: 003fffff00004004 ffffe6c6c07bfcc8 ffffe6c6c07bfcc8 0000000000000000 raw: 0000000000000000 0000000000000000 00000000fffffffe 0000000000000000 page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: dump_stack_lvl+0x32/0x50 bad_page+0x69/0xf0 free_unref_page_prepare+0x401/0x500 free_unref_page+0x6d/0x1b0 uprobe_write_opcode+0x460/0x8e0 install_breakpoint.part.0+0x51/0x80 register_for_each_vma+0x1d9/0x2b0 __uprobe_register+0x245/0x300 bpf_uprobe_multi_link_attach+0x29b/0x4f0 link_create+0x1e2/0x280 __sys_bpf+0x75f/0xac0 __x64_sys_bpf+0x1a/0x30 do_syscall_64+0x56/0x100 entry_SYSCALL_64_after_hwframe+0x78/0xe2 BUG: Bad rss-counter state mm:00000000452453e0 type:MM_FILEPAGES val:-1 The following syzkaller test case can be used to reproduce: r2 = creat(&(0x7f0000000000)='./file0\x00', 0x8) write$nbd(r2, &(0x7f0000000580)=ANY=[], 0x10) r4 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\x00', 0x42, 0x0) mmap$IORING_OFF_SQ_RING(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x0, 0x12, r4, 0x0) r5 = userfaultfd(0x80801) ioctl$UFFDIO_API(r5, 0xc018aa3f, &(0x7f0000000040)={0xaa, 0x20}) r6 = userfaultfd(0x80801) ioctl$UFFDIO_API(r6, 0xc018aa3f, &(0x7f0000000140)) ioctl$UFFDIO_REGISTER(r6, 0xc020aa00, &(0x7f0000000100)={{&(0x7f0000ffc000/0x4000)=nil, 0x4000}, 0x2}) ioctl$UFFDIO_ZEROPAGE(r5, 0xc020aa04, &(0x7f0000000000)={{&(0x7f0000ffd000/0x1000)=nil, 0x1000}}) r7 = bpf$PROG_LOAD(0x5, &(0x7f0000000140)={0x2, 0x3, &(0x7f0000000200)=ANY=[@ANYBLOB="1800000000120000000000000000000095"], &(0x7f0000000000)='GPL\x00', 0x7, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0, @fallback=0x30, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, @void, @value}, 0x94) bpf$BPF_LINK_CREATE_XDP(0x1c, &(0x7f0000000040)={r7, 0x0, 0x30, 0x1e, @val=@uprobe_multi={&(0x7f0000000080)='./file0\x00', &(0x7f0000000100)=[0x2], 0x0, 0x0, 0x1}}, 0x40) The cause is that zero pfn is set to the PTE without increasing the RSS count in mfill_atomic_pte_zeropage() and the refcount of zero folio does not increase accordingly. Then, the operation on the same pfn is performed in uprobe_write_opcode()->__replace_page() to unconditional decrease the RSS count and old_folio's refcount. Therefore, two bugs are introduced: 1. The RSS count is incorrect, when process exit, the check_mm() report error "Bad rss-count". 2. The reserved folio (zero folio) is freed when folio->refcount is zero, then free_pages_prepare->free_page_is_bad() report error "Bad page state". There is more, the following warning could also theoretically be triggered: __replace_page() -> ... -> folio_remove_rmap_pte() -> VM_WARN_ON_FOLIO(is_zero_folio(folio), folio) Considering that uprobe hit on the zero folio is a very rare case, just reject zero old folio immediately after get_user_page_vma_remote(). [ mingo: Cleaned up the changelog ] Fixes: 7396fa818d62 ("uprobes/core: Make background page replacement logic account for rss_stat counters") Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints") Signed-off-by: Tong Tiangen Signed-off-by: Ingo Molnar Reviewed-by: David Hildenbrand Reviewed-by: Oleg Nesterov Cc: Peter Zijlstra Cc: Masami Hiramatsu Link: https://lore.kernel.org/r/20250224031149.1598949-1-tongtiangen@huawei.com

perf/core: Order the PMU list to fix warning about unordered pmu_ctx_list

2025-02-24T18:22:37Z

Syskaller triggers a warning due to prev_epc->pmu != next_epc->pmu in perf_event_swap_task_ctx_data(). vmcore shows that two lists have the same perf_event_pmu_context, but not in the same order. The problem is that the order of pmu_ctx_list for the parent is impacted by the time when an event/PMU is added. While the order for a child is impacted by the event order in the pinned_groups and flexible_groups. So the order of pmu_ctx_list in the parent and child may be different. To fix this problem, insert the perf_event_pmu_context to its proper place after iteration of the pmu_ctx_list. The follow testcase can trigger above warning: # perf record -e cycles --call-graph lbr -- taskset -c 3 ./a.out & # perf stat -e cpu-clock,cs -p xxx // xxx is the pid of a.out test.c void main() { int count = 0; pid_t pid; printf("%d running\n", getpid()); sleep(30); printf("running\n"); pid = fork(); if (pid == -1) { printf("fork error\n"); return; } if (pid == 0) { while (1) { count++; } } else { while (1) { count++; } } } The testcase first opens an LBR event, so it will allocate task_ctx_data, and then open tracepoint and software events, so the parent context will have 3 different perf_event_pmu_contexts. On inheritance, child ctx will insert the perf_event_pmu_context in another order and the warning will trigger. [ mingo: Tidied up the changelog. ] Fixes: bd2756811766 ("perf: Rewrite core context handling") Signed-off-by: Luo Gengkun Signed-off-by: Ingo Molnar Reviewed-by: Kan Liang Link: https://lore.kernel.org/r/20250122073356.1824736-1-luogengkun@huaweicloud.com

perf/core: Add RCU read lock protection to perf_iterate_ctx()

2025-02-24T18:17:04Z

The perf_iterate_ctx() function performs RCU list traversal but currently lacks RCU read lock protection. This causes lockdep warnings when running perf probe with unshare(1) under CONFIG_PROVE_RCU_LIST=y: WARNING: suspicious RCU usage kernel/events/core.c:8168 RCU-list traversed in non-reader section!! Call Trace: lockdep_rcu_suspicious ? perf_event_addr_filters_apply perf_iterate_ctx perf_event_exec begin_new_exec ? load_elf_phdrs load_elf_binary ? lock_acquire ? find_held_lock ? bprm_execve bprm_execve do_execveat_common.isra.0 __x64_sys_execve do_syscall_64 entry_SYSCALL_64_after_hwframe This protection was previously present but was removed in commit bd2756811766 ("perf: Rewrite core context handling"). Add back the necessary rcu_read_lock()/rcu_read_unlock() pair around perf_iterate_ctx() call in perf_event_exec(). [ mingo: Use scoped_guard() as suggested by Peter ] Fixes: bd2756811766 ("perf: Rewrite core context handling") Signed-off-by: Breno Leitao Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250117-fix_perf_rcu-v1-1-13cb9210fc6a@debian.org

uprobes: Don't use %pK through printk

2025-02-18T08:48:02Z

Restricted pointers ("%pK") are not meant to be used through printk(). It can unintentionally expose security sensitive, raw pointer values. Use regular pointer formatting instead. For more background, see: https://lore.kernel.org/lkml/20250113171731-dc10e3c1-da64-4af0-b767-7c7070468023@linutronix.de/ Signed-off-by: Thomas Weißschuh Signed-off-by: Ingo Molnar Cc: Masami Hiramatsu Cc: Oleg Nesterov Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20250217-restricted-pointers-uprobes-v1-1-e8cbe5bb22a7@linutronix.de

kernel: be more careful about dup_mmap() failures and uprobe registering

2025-02-01T11:53:25Z

If a memory allocation fails during dup_mmap(), the maple tree can be left in an unsafe state for other iterators besides the exit path. All the locks are dropped before the exit_mmap() call (in mm/mmap.c), but the incomplete mm_struct can be reached through (at least) the rmap finding the vmas which have a pointer back to the mm_struct. Up to this point, there have been no issues with being able to find an mm_struct that was only partially initialised. Syzbot was able to make the incomplete mm_struct fail with recent forking changes, so it has been proven unsafe to use the mm_struct that hasn't been initialised, as referenced in the link below. Although 8ac662f5da19f ("fork: avoid inappropriate uprobe access to invalid mm") fixed the uprobe access, it does not completely remove the race. This patch sets the MMF_OOM_SKIP to avoid the iteration of the vmas on the oom side (even though this is extremely unlikely to be selected as an oom victim in the race window), and sets MMF_UNSTABLE to avoid other potential users from using a partially initialised mm_struct. When registering vmas for uprobe, skip the vmas in an mm that is marked unstable. Modifying a vma in an unstable mm may cause issues if the mm isn't fully initialised. Link: https://lore.kernel.org/all/6756d273.050a0220.2477f.003d.GAE@google.com/ Link: https://lkml.kernel.org/r/20250127170221.1761366-1-Liam.Howlett@oracle.com Fixes: d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") Signed-off-by: Liam R. Howlett Reviewed-by: Lorenzo Stoakes Cc: Oleg Nesterov Cc: Masami Hiramatsu Cc: Jann Horn Cc: Peter Zijlstra Cc: Michal Hocko Cc: Peng Zhang Cc: Matthew Wilcox Signed-off-by: Andrew Morton

Merge tag 'perf-core-2025-01-20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-01-21T18:52:03Z

Pull performance events updates from Ingo Molnar: "Seqlock optimizations that arose in a perf context and were merged into the perf tree: - seqlock: Add raw_seqcount_try_begin (Suren Baghdasaryan) - mm: Convert mm_lock_seq to a proper seqcount (Suren Baghdasaryan) - mm: Introduce mmap_lock_speculate_{try_begin|retry} (Suren Baghdasaryan) - mm/gup: Use raw_seqcount_try_begin() (Peter Zijlstra) Core perf enhancements: - Reduce 'struct page' footprint of perf by mapping pages in advance (Lorenzo Stoakes) - Save raw sample data conditionally based on sample type (Yabin Cui) - Reduce sampling overhead by checking sample_type in perf_sample_save_callchain() and perf_sample_save_brstack() (Yabin Cui) - Export perf_exclude_event() (Namhyung Kim) Uprobes scalability enhancements: (Andrii Nakryiko) - Simplify find_active_uprobe_rcu() VMA checks - Add speculative lockless VMA-to-inode-to-uprobe resolution - Simplify session consumer tracking - Decouple return_instance list traversal and freeing - Ensure return_instance is detached from the list before freeing - Reuse return_instances between multiple uretprobes within task - Guard against kmemdup() failing in dup_return_instance() AMD core PMU driver enhancements: - Relax privilege filter restriction on AMD IBS (Namhyung Kim) AMD RAPL energy counters support: (Dhananjay Ugwekar) - Introduce topology_logical_core_id() (K Prateek Nayak) - Remove the unused get_rapl_pmu_cpumask() function - Remove the cpu_to_rapl_pmu() function - Rename rapl_pmu variables - Make rapl_model struct global - Add arguments to the init and cleanup functions - Modify the generic variable names to *_pkg* - Remove the global variable rapl_msrs - Move the cntr_mask to rapl_pmus struct - Add core energy counter support for AMD CPUs Intel core PMU driver enhancements: - Support RDPMC 'metrics clear mode' feature (Kan Liang) - Clarify adaptive PEBS processing (Kan Liang) - Factor out functions for PEBS records processing (Kan Liang) - Simplify the PEBS records processing for adaptive PEBS (Kan Liang) Intel uncore driver enhancements: (Kan Liang) - Convert buggy pmu->func_id use to pmu->registered - Support more units on Granite Rapids" * tag 'perf-core-2025-01-20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits) perf: map pages in advance perf/x86/intel/uncore: Support more units on Granite Rapids perf/x86/intel/uncore: Clean up func_id perf/x86/intel: Support RDPMC metrics clear mode uprobes: Guard against kmemdup() failing in dup_return_instance() perf/x86: Relax privilege filter restriction on AMD IBS perf/core: Export perf_exclude_event() uprobes: Reuse return_instances between multiple uretprobes within task uprobes: Ensure return_instance is detached from the list before freeing uprobes: Decouple return_instance list traversal and freeing uprobes: Simplify session consumer tracking uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution uprobes: simplify find_active_uprobe_rcu() VMA checks mm: introduce mmap_lock_speculate_{try_begin|retry} mm: convert mm_lock_seq to a proper seqcount mm/gup: Use raw_seqcount_try_begin() seqlock: add raw_seqcount_try_begin perf/x86/rapl: Add core energy counter support for AMD CPUs perf/x86/rapl: Move the cntr_mask to rapl_pmus struct perf/x86/rapl: Remove the global variable rapl_msrs ...