linux-stable.git/kernel, branch linux-6.4.y

tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY

2023-09-13T07:48:45+00:00

commit 3d07fa1dd19035eb0b13ae6697efd5caa9033e74 upstream.

The pipe cpumask used to serialize opens between the main and percpu
trace pipes is not zeroed or initialized. This can result in
spurious -EBUSY returns if underlying memory is not fully zeroed.
This has been observed by immediate failure to read the main
trace_pipe file on an otherwise newly booted and idle system:

 # cat /sys/kernel/debug/tracing/trace_pipe
 cat: /sys/kernel/debug/tracing/trace_pipe: Device or resource busy

Zero the allocation of pipe_cpumask to avoid the problem.

Link: https://lore.kernel.org/linux-trace-kernel/20230831125500.986862-1-bfoster@redhat.com

Cc: stable@vger.kernel.org
Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
Reviewed-by: Zheng Yejian 
Reviewed-by: Masami Hiramatsu (Google) 
Signed-off-by: Brian Foster 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

bpf: Fix issue in verifying allow_ptr_leaks

2023-09-13T07:48:41+00:00

commit d75e30dddf73449bc2d10bb8e2f1a2c446bc67a2 upstream.

After we converted the capabilities of our networking-bpf program from
cap_sys_admin to cap_net_admin+cap_bpf, our networking-bpf program
failed to start. Because it failed the bpf verifier, and the error log
is "R3 pointer comparison prohibited".

A simple reproducer as follows,

SEC("cls-ingress")
int ingress(struct __sk_buff *skb)
{
	struct iphdr *iph = (void *)(long)skb->data + sizeof(struct ethhdr);

	if ((long)(iph + 1) > (long)skb->data_end)
		return TC_ACT_STOLEN;
	return TC_ACT_OK;
}

Per discussion with Yonghong and Alexei [1], comparison of two packet
pointers is not a pointer leak. This patch fixes it.

Our local kernel is 6.1.y and we expect this fix to be backported to
6.1.y, so stable is CCed.

[1]. https://lore.kernel.org/bpf/CAADnVQ+Nmspr7Si+pxWn8zkE7hX-7s93ugwC+94aXSy4uQ9vBg@mail.gmail.com/

Suggested-by: Yonghong Song 
Suggested-by: Alexei Starovoitov 
Signed-off-by: Yafang Shao 
Acked-by: Eduard Zingerman 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230823020703.3790-2-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Greg Kroah-Hartman

cpu/hotplug: Prevent self deadlock on CPU hot-unplug

2023-09-13T07:48:38+00:00

commit 2b8272ff4a70b866106ae13c36be7ecbef5d5da2 upstream.

Xiongfeng reported and debugged a self deadlock of the task which initiates
and controls a CPU hot-unplug operation vs. the CFS bandwidth timer.

    CPU1      			                 	 CPU2

T1 sets cfs_quota
   starts hrtimer cfs_bandwidth 'period_timer'
T1 is migrated to CPU2
						T1 initiates offlining of CPU1
Hotplug operation starts
  ...
'period_timer' expires and is re-enqueued on CPU1
  ...
take_cpu_down()
  CPU1 shuts down and does not handle timers
  anymore. They have to be migrated in the
  post dead hotplug steps by the control task.

						T1 runs the post dead offline operation
					      	T1 is scheduled out
						T1 waits for 'period_timer' to expire

T1 waits there forever if it is scheduled out before it can execute the hrtimer
offline callback hrtimers_dead_cpu().

Cure this by delegating the hotplug control operation to a worker thread on
an online CPU. This takes the initiating user space task, which might be
affected by the bandwidth timer, completely out of the picture.

Reported-by: Xiongfeng Wang 
Signed-off-by: Thomas Gleixner 
Tested-by: Yu Liao 
Acked-by: Vincent Guittot 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/lkml/8e785777-03aa-99e1-d20e-e956f5685be6@huawei.com
Link: https://lore.kernel.org/r/87h6oqdq0i.ffs@tglx
Signed-off-by: Greg Kroah-Hartman

printk: ringbuffer: Fix truncating buffer size min_t cast

2023-09-13T07:48:38+00:00

commit 53e9e33ede37a247d926db5e4a9e56b55204e66c upstream.

If an output buffer size exceeded U16_MAX, the min_t(u16, ...) cast in
copy_data() was causing writes to truncate. This manifested as output
bytes being skipped, seen as %NUL bytes in pstore dumps when the available
record size was larger than 65536. Fix the cast to no longer truncate
the calculation.

Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Cc: John Ogness 
Reported-by: Vijay Balakrishna 
Link: https://lore.kernel.org/lkml/d8bb1ec7-a4c5-43a2-9de0-9643a70b899f@linux.microsoft.com/
Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook 
Tested-by: Vijay Balakrishna 
Tested-by: Guilherme G. Piccoli  # Steam Deck
Reviewed-by: Tyler Hicks (Microsoft) 
Tested-by: Tyler Hicks (Microsoft) 
Reviewed-by: John Ogness 
Reviewed-by: Sergey Senozhatsky 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20230811054528.never.165-kees@kernel.org
Signed-off-by: Greg Kroah-Hartman

tracing: Fix race issue between cpu buffer write and swap

2023-09-13T07:48:34+00:00

[ Upstream commit 3163f635b20e9e1fb4659e74f47918c9dddfe64e ]

Warning happened in rb_end_commit() at code:
	if (RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing)))

  WARNING: CPU: 0 PID: 139 at kernel/trace/ring_buffer.c:3142
	rb_commit+0x402/0x4a0
  Call Trace:
   ring_buffer_unlock_commit+0x42/0x250
   trace_buffer_unlock_commit_regs+0x3b/0x250
   trace_event_buffer_commit+0xe5/0x440
   trace_event_buffer_reserve+0x11c/0x150
   trace_event_raw_event_sched_switch+0x23c/0x2c0
   __traceiter_sched_switch+0x59/0x80
   __schedule+0x72b/0x1580
   schedule+0x92/0x120
   worker_thread+0xa0/0x6f0

It is because the race between writing event into cpu buffer and swapping
cpu buffer through file per_cpu/cpu0/snapshot:

  Write on CPU 0             Swap buffer by per_cpu/cpu0/snapshot on CPU 1
  --------                   --------
                             tracing_snapshot_write()
                               [...]

  ring_buffer_lock_reserve()
    cpu_buffer = buffer->buffers[cpu]; // 1. Suppose find 'cpu_buffer_a';
    [...]
    rb_reserve_next_event()
      [...]

                               ring_buffer_swap_cpu()
                                 if (local_read(&cpu_buffer_a->committing))
                                     goto out_dec;
                                 if (local_read(&cpu_buffer_b->committing))
                                     goto out_dec;
                                 buffer_a->buffers[cpu] = cpu_buffer_b;
                                 buffer_b->buffers[cpu] = cpu_buffer_a;
                                 // 2. cpu_buffer has swapped here.

      rb_start_commit(cpu_buffer);
      if (unlikely(READ_ONCE(cpu_buffer->buffer)
          != buffer)) { // 3. This check passed due to 'cpu_buffer->buffer'
        [...]           //    has not changed here.
        return NULL;
      }
                                 cpu_buffer_b->buffer = buffer_a;
                                 cpu_buffer_a->buffer = buffer_b;
                                 [...]

      // 4. Reserve event from 'cpu_buffer_a'.

  ring_buffer_unlock_commit()
    [...]
    cpu_buffer = buffer->buffers[cpu]; // 5. Now find 'cpu_buffer_b' !!!
    rb_commit(cpu_buffer)
      rb_end_commit()  // 6. WARN for the wrong 'committing' state !!!

Based on above analysis, we can easily reproduce by following testcase:
  ``` bash
  #!/bin/bash

  dmesg -n 7
  sysctl -w kernel.panic_on_warn=1
  TR=/sys/kernel/tracing
  echo 7 > ${TR}/buffer_size_kb
  echo "sched:sched_switch" > ${TR}/set_event
  while [ true ]; do
          echo 1 > ${TR}/per_cpu/cpu0/snapshot
  done &
  while [ true ]; do
          echo 1 > ${TR}/per_cpu/cpu0/snapshot
  done &
  while [ true ]; do
          echo 1 > ${TR}/per_cpu/cpu0/snapshot
  done &
  ```

To fix it, IIUC, we can use smp_call_function_single() to do the swap on
the target cpu where the buffer is located, so that above race would be
avoided.

Link: https://lore.kernel.org/linux-trace-kernel/20230831132739.4070878-1-zhengyejian1@huawei.com

Cc: 
Fixes: f1affcaaa861 ("tracing: Add snapshot in the per_cpu trace directories")
Signed-off-by: Zheng Yejian 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Sasha Levin

tracing: Remove extra space at the end of hwlat_detector/mode

2023-09-13T07:48:34+00:00

[ Upstream commit 2cf0dee989a8b2501929eaab29473b6b1fa11057 ]

Space is printed after each mode value including the last one:
$ echo \"$(sudo cat /sys/kernel/tracing/hwlat_detector/mode)\"
"none [round-robin] per-cpu "

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Link: https://lore.kernel.org/linux-trace-kernel/20230825103432.7750-1-m.kobuk@ispras.ru

Cc: Masami Hiramatsu 
Fixes: 8fa826b7344d ("trace/hwlat: Implement the mode config option")
Signed-off-by: Mikhail Kobuk 
Reviewed-by: Alexey Khoroshilov 
Acked-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Sasha Levin

tick/rcu: Fix false positive "softirq work is pending" messages

2023-09-13T07:48:34+00:00

[ Upstream commit 96c1fa04f089a7e977a44e4e8fdc92e81be20bef ]

In commit 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle") the
new function report_idle_softirq() was created by breaking code out of the
existing can_stop_idle_tick() for kernels v5.18 and newer.

In doing so, the code essentially went from a one conditional:

	if (a && b && c)
		warn();

to a three conditional:

	if (!a)
		return;
	if (!b)
		return;
	if (!c)
		return;
	warn();

But that conversion got the condition for the RT specific
local_bh_blocked() wrong. The original condition was:

   	!local_bh_blocked()

but the conversion failed to negate it so it ended up as:

        if (!local_bh_blocked())
		return false;

This issue lay dormant until another fixup for the same commit was added
in commit a7e282c77785 ("tick/rcu: Fix bogus ratelimit condition").
This commit realized the ratelimit was essentially set to zero instead
of ten, and hence *no* softirq pending messages would ever be issued.

Once this commit was backported via linux-stable, both the v6.1 and v6.4
preempt-rt kernels started printing out 10 instances of this at boot:

  NOHZ tick-stop error: local softirq work is pending, handler #80!!!

Remove the negation and return when local_bh_blocked() evaluates to true to
bring the correct behaviour back.

Fixes: 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle")
Signed-off-by: Paul Gortmaker 
Signed-off-by: Thomas Gleixner 
Tested-by: Ahmad Fatoum 
Reviewed-by: Wen Yang 
Acked-by: Frederic Weisbecker 
Link: https://lore.kernel.org/r/20230818200757.1808398-1-paul.gortmaker@windriver.com
Signed-off-by: Sasha Levin

cgroup/cpuset: Inherit parent's load balance state in v2

2023-09-13T07:48:25+00:00

[ Upstream commit c8c926200c55454101f072a4b16c9ff5b8c9e56f ]

Since commit f28e22441f35 ("cgroup/cpuset: Add a new isolated
cpus.partition type"), the CS_SCHED_LOAD_BALANCE bit of a v2 cpuset
can be on or off. The child cpusets of a partition root must have the
same setting as its parent or it may screw up the rebuilding of sched
domains. Fix this problem by making sure the a child v2 cpuset will
follows its parent cpuset load balance state unless the child cpuset
is a new partition root itself.

Fixes: f28e22441f35 ("cgroup/cpuset: Add a new isolated cpus.partition type")
Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

audit: fix possible soft lockup in __audit_inode_child()

2023-09-13T07:48:17+00:00

[ Upstream commit b59bc6e37237e37eadf50cd5de369e913f524463 ]

Tracefs or debugfs maybe cause hundreds to thousands of PATH records,
too many PATH records maybe cause soft lockup.

For example:
  1. CONFIG_KASAN=y && CONFIG_PREEMPTION=n
  2. auditctl -a exit,always -S open -k key
  3. sysctl -w kernel.watchdog_thresh=5
  4. mkdir /sys/kernel/debug/tracing/instances/test

There may be a soft lockup as follows:
  watchdog: BUG: soft lockup - CPU#45 stuck for 7s! [mkdir:15498]
  Kernel panic - not syncing: softlockup: hung tasks
  Call trace:
   dump_backtrace+0x0/0x30c
   show_stack+0x20/0x30
   dump_stack+0x11c/0x174
   panic+0x27c/0x494
   watchdog_timer_fn+0x2bc/0x390
   __run_hrtimer+0x148/0x4fc
   __hrtimer_run_queues+0x154/0x210
   hrtimer_interrupt+0x2c4/0x760
   arch_timer_handler_phys+0x48/0x60
   handle_percpu_devid_irq+0xe0/0x340
   __handle_domain_irq+0xbc/0x130
   gic_handle_irq+0x78/0x460
   el1_irq+0xb8/0x140
   __audit_inode_child+0x240/0x7bc
   tracefs_create_file+0x1b8/0x2a0
   trace_create_file+0x18/0x50
   event_create_dir+0x204/0x30c
   __trace_add_new_event+0xac/0x100
   event_trace_add_tracer+0xa0/0x130
   trace_array_create_dir+0x60/0x140
   trace_array_create+0x1e0/0x370
   instance_mkdir+0x90/0xd0
   tracefs_syscall_mkdir+0x68/0xa0
   vfs_mkdir+0x21c/0x34c
   do_mkdirat+0x1b4/0x1d4
   __arm64_sys_mkdirat+0x4c/0x60
   el0_svc_common.constprop.0+0xa8/0x240
   do_el0_svc+0x8c/0xc0
   el0_svc+0x20/0x30
   el0_sync_handler+0xb0/0xb4
   el0_sync+0x160/0x180

Therefore, we add cond_resched() to __audit_inode_child() to fix it.

Fixes: 5195d8e217a7 ("audit: dynamically allocate audit_names when not enough space is in the names array")
Signed-off-by: Gaosheng Cui 
Signed-off-by: Paul Moore 
Signed-off-by: Sasha Levin

bpf: Fix check_func_arg_reg_off bug for graph root/node

2023-09-13T07:48:06+00:00

[ Upstream commit 6785b2edf48c6b1c3ea61fe3b0d2e02b8fbf90c0 ]

The commit being fixed introduced a hunk into check_func_arg_reg_off
that bypasses reg->off == 0 enforcement when offset points to a graph
node or root. This might possibly be done for treating bpf_rbtree_remove
and others as KF_RELEASE and then later check correct reg->off in helper
argument checks.

But this is not the case, those helpers are already not KF_RELEASE and
permit non-zero reg->off and verify it later to match the subobject in
BTF type.

However, this logic leads to bpf_obj_drop permitting free of register
arguments with non-zero offset when they point to a graph root or node
within them, which is not ok.

For instance:

struct foo {
	int i;
	int j;
	struct bpf_rb_node node;
};

struct foo *f = bpf_obj_new(typeof(*f));
if (!f) ...
bpf_obj_drop(f); // OK
bpf_obj_drop(&f->i); // still ok from verifier PoV
bpf_obj_drop(&f->node); // Not OK, but permitted right now

Fix this by dropping the whole part of code altogether.

Fixes: 6a3cd3318ff6 ("bpf: Migrate release_on_unlock logic to non-owning ref semantics")
Signed-off-by: Kumar Kartikeya Dwivedi 
Link: https://lore.kernel.org/r/20230822175140.1317749-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin