linux-toradex.git/kernel/bpf, branch v5.9-rc7

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

2020-09-16T02:26:21+00:00

Alexei Starovoitov says:

====================
pull-request: bpf 2020-09-15

The following pull-request contains BPF updates for your *net* tree.

We've added 12 non-merge commits during the last 19 day(s) which contain
a total of 10 files changed, 47 insertions(+), 38 deletions(-).

The main changes are:

1) docs/bpf fixes, from Andrii.

2) ld_abs fix, from Daniel.

3) socket casting helpers fix, from Martin.

4) hash iterator fixes, from Yonghong.
====================

Signed-off-by: David S. Miller

bpf: Fix a rcu warning for bpffs map pretty-print

2020-09-16T01:17:39+00:00

Running selftest
  ./btf_btf -p
the kernel had the following warning:
  [   51.528185] WARNING: CPU: 3 PID: 1756 at kernel/bpf/hashtab.c:717 htab_map_get_next_key+0x2eb/0x300
  [   51.529217] Modules linked in:
  [   51.529583] CPU: 3 PID: 1756 Comm: test_btf Not tainted 5.9.0-rc1+ #878
  [   51.530346] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.el7.centos 04/01/2014
  [   51.531410] RIP: 0010:htab_map_get_next_key+0x2eb/0x300
  ...
  [   51.542826] Call Trace:
  [   51.543119]  map_seq_next+0x53/0x80
  [   51.543528]  seq_read+0x263/0x400
  [   51.543932]  vfs_read+0xad/0x1c0
  [   51.544311]  ksys_read+0x5f/0xe0
  [   51.544689]  do_syscall_64+0x33/0x40
  [   51.545116]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

The related source code in kernel/bpf/hashtab.c:
  709 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
  710 {
  711         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  712         struct hlist_nulls_head *head;
  713         struct htab_elem *l, *next_l;
  714         u32 hash, key_size;
  715         int i = 0;
  716
  717         WARN_ON_ONCE(!rcu_read_lock_held());

In kernel/bpf/inode.c, bpffs map pretty print calls map->ops->map_get_next_key()
without holding a rcu_read_lock(), hence causing the above warning.
To fix the issue, just surrounding map->ops->map_get_next_key() with rcu read lock.

Fixes: a26ca7c982cb ("bpf: btf: Add pretty print support to the basic arraymap")
Reported-by: Alexei Starovoitov 
Signed-off-by: Yonghong Song 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Cc: Martin KaFai Lau 
Link: https://lore.kernel.org/bpf/20200916004401.146277-1-yhs@fb.com

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2020-09-04T01:50:48+00:00

Pull networking fixes from David Miller:

 1) Use netif_rx_ni() when necessary in batman-adv stack, from Jussi
    Kivilinna.

 2) Fix loss of RTT samples in rxrpc, from David Howells.

 3) Memory leak in hns_nic_dev_probe(), from Dignhao Liu.

 4) ravb module cannot be unloaded, fix from Yuusuke Ashizuka.

 5) We disable BH for too lokng in sctp_get_port_local(), add a
    cond_resched() here as well, from Xin Long.

 6) Fix memory leak in st95hf_in_send_cmd, from Dinghao Liu.

 7) Out of bound access in bpf_raw_tp_link_fill_link_info(), from
    Yonghong Song.

 8) Missing of_node_put() in mt7530 DSA driver, from Sumera
    Priyadarsini.

 9) Fix crash in bnxt_fw_reset_task(), from Michael Chan.

10) Fix geneve tunnel checksumming bug in hns3, from Yi Li.

11) Memory leak in rxkad_verify_response, from Dinghao Liu.

12) In tipc, don't use smp_processor_id() in preemptible context. From
    Tuong Lien.

13) Fix signedness issue in mlx4 memory allocation, from Shung-Hsi Yu.

14) Missing clk_disable_prepare() in gemini driver, from Dan Carpenter.

15) Fix ABI mismatch between driver and firmware in nfp, from Louis
    Peens.

* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (110 commits)
  net/smc: fix sock refcounting in case of termination
  net/smc: reset sndbuf_desc if freed
  net/smc: set rx_off for SMCR explicitly
  net/smc: fix toleration of fake add_link messages
  tg3: Fix soft lockup when tg3_reset_task() fails.
  doc: net: dsa: Fix typo in config code sample
  net: dp83867: Fix WoL SecureOn password
  nfp: flower: fix ABI mismatch between driver and firmware
  tipc: fix shutdown() of connectionless socket
  ipv6: Fix sysctl max for fib_multipath_hash_policy
  drivers/net/wan/hdlc: Change the default of hard_header_len to 0
  net: gemini: Fix another missing clk_disable_unprepare() in probe
  net: bcmgenet: fix mask check in bcmgenet_validate_flow()
  amd-xgbe: Add support for new port mode
  net: usb: dm9601: Add USB ID of Keenetic Plus DSL
  vhost: fix typo in error message
  net: ethernet: mlx4: Fix memory allocation in mlx4_buddy_init()
  pktgen: fix error message with wrong function name
  net: ethernet: ti: am65-cpsw: fix rmii 100Mbit link mode
  cxgb4: fix thermal zone device registration
  ...

bpf: Do not use bucket_lock for hashmap iterator

2020-09-04T00:36:41+00:00

Currently, for hashmap, the bpf iterator will grab a bucket lock, a
spinlock, before traversing the elements in the bucket. This can ensure
all bpf visted elements are valid. But this mechanism may cause
deadlock if update/deletion happens to the same bucket of the
visited map in the program. For example, if we added bpf_map_update_elem()
call to the same visited element in selftests bpf_iter_bpf_hash_map.c,
we will have the following deadlock:

  ============================================
  WARNING: possible recursive locking detected
  5.9.0-rc1+ #841 Not tainted
  --------------------------------------------
  test_progs/1750 is trying to acquire lock:
  ffff9a5bb73c5e70 (&htab->buckets[i].raw_lock){....}-{2:2}, at: htab_map_update_elem+0x1cf/0x410

  but task is already holding lock:
  ffff9a5bb73c5e20 (&htab->buckets[i].raw_lock){....}-{2:2}, at: bpf_hash_map_seq_find_next+0x94/0x120

  other info that might help us debug this:
   Possible unsafe locking scenario:

         CPU0
         ----
    lock(&htab->buckets[i].raw_lock);
    lock(&htab->buckets[i].raw_lock);

   *** DEADLOCK ***
   ...
  Call Trace:
   dump_stack+0x78/0xa0
   __lock_acquire.cold.74+0x209/0x2e3
   lock_acquire+0xba/0x380
   ? htab_map_update_elem+0x1cf/0x410
   ? __lock_acquire+0x639/0x20c0
   _raw_spin_lock_irqsave+0x3b/0x80
   ? htab_map_update_elem+0x1cf/0x410
   htab_map_update_elem+0x1cf/0x410
   ? lock_acquire+0xba/0x380
   bpf_prog_ad6dab10433b135d_dump_bpf_hash_map+0x88/0xa9c
   ? find_held_lock+0x34/0xa0
   bpf_iter_run_prog+0x81/0x16e
   __bpf_hash_map_seq_show+0x145/0x180
   bpf_seq_read+0xff/0x3d0
   vfs_read+0xad/0x1c0
   ksys_read+0x5f/0xe0
   do_syscall_64+0x33/0x40
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  ...

The bucket_lock first grabbed in seq_ops->next() called by bpf_seq_read(),
and then grabbed again in htab_map_update_elem() in the bpf program, causing
deadlocks.

Actually, we do not need bucket_lock here, we can just use rcu_read_lock()
similar to netlink iterator where the rcu_read_{lock,unlock} likes below:
 seq_ops->start():
     rcu_read_lock();
 seq_ops->next():
     rcu_read_unlock();
     /* next element */
     rcu_read_lock();
 seq_ops->stop();
     rcu_read_unlock();

Compared to old bucket_lock mechanism, if concurrent updata/delete happens,
we may visit stale elements, miss some elements, or repeat some elements.
I think this is a reasonable compromise. For users wanting to avoid
stale, missing/repeated accesses, bpf_map batch access syscall interface
can be used.

Signed-off-by: Yonghong Song 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20200902235340.2001375-1-yhs@fb.com

bpf: Fix a buffer out-of-bound access when filling raw_tp link_info

2020-08-25T04:03:07+00:00

Commit f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
added link query for raw_tp. One of fields in link_info is to
fill a user buffer with tp_name. The Scurrent checking only
declares "ulen && !ubuf" as invalid. So "!ulen && ubuf" will be
valid. Later on, we do "copy_to_user(ubuf, tp_name, ulen - 1)" which
may overwrite user memory incorrectly.

This patch fixed the problem by disallowing "!ulen && ubuf" case as well.

Fixes: f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
Signed-off-by: Yonghong Song 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20200821191054.714731-1-yhs@fb.com

treewide: Use fallthrough pseudo-keyword

2020-08-23T22:36:59+00:00

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva

bpf: Avoid visit same object multiple times

2020-08-19T00:36:23+00:00

Currently when traversing all tasks, the next tid
is always increased by one. This may result in
visiting the same task multiple times in a
pid namespace.

This patch fixed the issue by seting the next
tid as pid_nr_ns(pid, ns) + 1, similar to
funciton next_tgid().

Signed-off-by: Yonghong Song 
Signed-off-by: Alexei Starovoitov 
Cc: Rik van Riel 
Link: https://lore.kernel.org/bpf/20200818222310.2181500-1-yhs@fb.com

bpf: Fix a rcu_sched stall issue with bpf task/task_file iterator

2020-08-19T00:36:23+00:00

In our production system, we observed rcu stalls when
'bpftool prog` is running.
  rcu: INFO: rcu_sched self-detected stall on CPU
  rcu: \x097-....: (20999 ticks this GP) idle=302/1/0x4000000000000000 softirq=1508852/1508852 fqs=4913
  \x09(t=21031 jiffies g=2534773 q=179750)
  NMI backtrace for cpu 7
  CPU: 7 PID: 184195 Comm: bpftool Kdump: loaded Tainted: G        W         5.8.0-00004-g68bfc7f8c1b4 #6
  Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A17 05/03/2019
  Call Trace:
  
  dump_stack+0x57/0x70
  nmi_cpu_backtrace.cold+0x14/0x53
  ? lapic_can_unplug_cpu.cold+0x39/0x39
  nmi_trigger_cpumask_backtrace+0xb7/0xc7
  rcu_dump_cpu_stacks+0xa2/0xd0
  rcu_sched_clock_irq.cold+0x1ff/0x3d9
  ? tick_nohz_handler+0x100/0x100
  update_process_times+0x5b/0x90
  tick_sched_timer+0x5e/0xf0
  __hrtimer_run_queues+0x12a/0x2a0
  hrtimer_interrupt+0x10e/0x280
  __sysvec_apic_timer_interrupt+0x51/0xe0
  asm_call_on_stack+0xf/0x20
  
  sysvec_apic_timer_interrupt+0x6f/0x80
  asm_sysvec_apic_timer_interrupt+0x12/0x20
  RIP: 0010:task_file_seq_get_next+0x71/0x220
  Code: 00 00 8b 53 1c 49 8b 7d 00 89 d6 48 8b 47 20 44 8b 18 41 39 d3 76 75 48 8b 4f 20 8b 01 39 d0 76 61 41 89 d1 49 39 c1 48 19 c0 <48> 8b 49 08 21 d0 48 8d 04 c1 4c 8b 08 4d 85 c9 74 46 49 8b 41 38
  RSP: 0018:ffffc90006223e10 EFLAGS: 00000297
  RAX: ffffffffffffffff RBX: ffff888f0d172388 RCX: ffff888c8c07c1c0
  RDX: 00000000000f017b RSI: 00000000000f017b RDI: ffff888c254702c0
  RBP: ffffc90006223e68 R08: ffff888be2a1c140 R09: 00000000000f017b
  R10: 0000000000000002 R11: 0000000000100000 R12: ffff888f23c24118
  R13: ffffc90006223e60 R14: ffffffff828509a0 R15: 00000000ffffffff
  task_file_seq_next+0x52/0xa0
  bpf_seq_read+0xb9/0x320
  vfs_read+0x9d/0x180
  ksys_read+0x5f/0xe0
  do_syscall_64+0x38/0x60
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f8815f4f76e
  Code: c0 e9 f6 fe ff ff 55 48 8d 3d 76 70 0a 00 48 89 e5 e8 36 06 02 00 66 0f 1f 44 00 00 64 8b 04 25 18 00 00 00 85 c0 75 14 0f 05 <48> 3d 00 f0 ff ff 77 52 c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5
  RSP: 002b:00007fff8f9df578 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
  RAX: ffffffffffffffda RBX: 000000000170b9c0 RCX: 00007f8815f4f76e
  RDX: 0000000000001000 RSI: 00007fff8f9df5b0 RDI: 0000000000000007
  RBP: 00007fff8f9e05f0 R08: 0000000000000049 R09: 0000000000000010
  R10: 00007f881601fa40 R11: 0000000000000246 R12: 00007fff8f9e05a8
  R13: 00007fff8f9e05a8 R14: 0000000001917f90 R15: 000000000000e22e

Note that `bpftool prog` actually calls a task_file bpf iterator
program to establish an association between prog/map/link/btf anon
files and processes.

In the case where the above rcu stall occured, we had a process
having 1587 tasks and each task having roughly 81305 files.
This implied 129 million bpf prog invocations. Unfortunwtely none of
these files are prog/map/link/btf files so bpf iterator/prog needs
to traverse all these files and not able to return to user space
since there are no seq_file buffer overflow.

This patch fixed the issue in bpf_seq_read() to limit the number
of visited objects. If the maximum number of visited objects is
reached, no more objects will be visited in the current syscall.
If there is nothing written in the seq_file buffer, -EAGAIN will
return to the user so user can try again.

The maximum number of visited objects is set at 1 million.
In our Intel Xeon D-2191 2.3GHZ 18-core server, bpf_seq_read()
visiting 1 million files takes around 0.18 seconds.

We did not use cond_resched() since for some iterators, e.g.,
netlink iterator, where rcu read_lock critical section spans between
consecutive seq_ops->next(), which makes impossible to do cond_resched()
in the key while loop of function bpf_seq_read().

Signed-off-by: Yonghong Song 
Signed-off-by: Alexei Starovoitov 
Cc: Paul E. McKenney 
Link: https://lore.kernel.org/bpf/20200818222309.2181348-1-yhs@fb.com

bpf: Use get_file_rcu() instead of get_file() for task_file iterator

2020-08-17T21:42:58+00:00

With latest `bpftool prog` command, we observed the following kernel
panic.
    BUG: kernel NULL pointer dereference, address: 0000000000000000
    #PF: supervisor instruction fetch in kernel mode
    #PF: error_code(0x0010) - not-present page
    PGD dfe894067 P4D dfe894067 PUD deb663067 PMD 0
    Oops: 0010 [#1] SMP
    CPU: 9 PID: 6023 ...
    RIP: 0010:0x0
    Code: Bad RIP value.
    RSP: 0000:ffffc900002b8f18 EFLAGS: 00010286
    RAX: ffff8883a405f400 RBX: ffff888e46a6bf00 RCX: 000000008020000c
    RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8883a405f400
    RBP: ffff888e46a6bf50 R08: 0000000000000000 R09: ffffffff81129600
    R10: ffff8883a405f300 R11: 0000160000000000 R12: 0000000000002710
    R13: 000000e9494b690c R14: 0000000000000202 R15: 0000000000000009
    FS:  00007fd9187fe700(0000) GS:ffff888e46a40000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffffffffffffffd6 CR3: 0000000de5d33002 CR4: 0000000000360ee0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     
     rcu_core+0x1a4/0x440
     __do_softirq+0xd3/0x2c8
     irq_exit+0x9d/0xa0
     smp_apic_timer_interrupt+0x68/0x120
     apic_timer_interrupt+0xf/0x20
     
    RIP: 0033:0x47ce80
    Code: Bad RIP value.
    RSP: 002b:00007fd9187fba40 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
    RAX: 0000000000000002 RBX: 00007fd931789160 RCX: 000000000000010c
    RDX: 00007fd9308cdfb4 RSI: 00007fd9308cdfb4 RDI: 00007ffedd1ea0a8
    RBP: 00007fd9187fbab0 R08: 000000000000000e R09: 000000000000002a
    R10: 0000000000480210 R11: 00007fd9187fc570 R12: 00007fd9316cc400
    R13: 0000000000000118 R14: 00007fd9308cdfb4 R15: 00007fd9317a9380

After further analysis, the bug is triggered by
Commit eaaacd23910f ("bpf: Add task and task/file iterator targets")
which introduced task_file bpf iterator, which traverses all open file
descriptors for all tasks in the current namespace.
The latest `bpftool prog` calls a task_file bpf program to traverse
all files in the system in order to associate processes with progs/maps, etc.
When traversing files for a given task, rcu read_lock is taken to
access all files in a file_struct. But it used get_file() to grab
a file, which is not right. It is possible file->f_count is 0 and
get_file() will unconditionally increase it.
Later put_file() may cause all kind of issues with the above
as one of sympotoms.

The failure can be reproduced with the following steps in a few seconds:
    $ cat t.c
    #include 
    #include 
    #include 
    #include 
    #include 

    #define N 10000
    int fd[N];
    int main() {
      int i;

      for (i = 0; i < N; i++) {
        fd[i] = open("./note.txt", 'r');
        if (fd[i] < 0) {
           fprintf(stderr, "failed\n");
           return -1;
        }
      }
      for (i = 0; i < N; i++)
        close(fd[i]);

      return 0;
    }
    $ gcc -O2 t.c
    $ cat run.sh
    #/bin/bash
    for i in {1..100}
    do
      while true; do ./a.out; done &
    done
    $ ./run.sh
    $ while true; do bpftool prog >& /dev/null; done

This patch used get_file_rcu() which only grabs a file if the
file->f_count is not zero. This is to ensure the file pointer
is always valid. The above reproducer did not fail for more
than 30 minutes.

Fixes: eaaacd23910f ("bpf: Add task and task/file iterator targets")
Suggested-by: Josef Bacik 
Signed-off-by: Yonghong Song 
Signed-off-by: Alexei Starovoitov 
Reviewed-by: Josef Bacik 
Link: https://lore.kernel.org/bpf/20200817174214.252601-1-yhs@fb.com

bpf: Iterate through all PT_NOTE sections when looking for build id

2020-08-13T01:14:49+00:00

Currently when we look for build id within bpf_get_stackid helper
call, we check the first NOTE section and we fail if build id is
not there.

However on some system (Fedora) there can be multiple NOTE sections
in binaries and build id data is not always the first one, like:

  $ readelf -a /usr/bin/ls
  ...
  [ 2] .note.gnu.propert NOTE             0000000000000338  00000338
       0000000000000020  0000000000000000   A       0     0     8358
  [ 3] .note.gnu.build-i NOTE             0000000000000358  00000358
       0000000000000024  0000000000000000   A       0     0     437c
  [ 4] .note.ABI-tag     NOTE             000000000000037c  0000037c
  ...

So the stack_map_get_build_id function will fail on build id retrieval
and fallback to BPF_STACK_BUILD_ID_IP.

This patch is changing the stack_map_get_build_id code to iterate
through all the NOTE sections and try to get build id data from
each of them.

When tracing on sched_switch tracepoint that does bpf_get_stackid
helper call kernel build, I can see about 60% increase of successful
build id retrieval. The rest seems fails on -EFAULT.

Signed-off-by: Jiri Olsa 
Signed-off-by: Alexei Starovoitov 
Acked-by: Song Liu 
Link: https://lore.kernel.org/bpf/20200812123102.20032-1-jolsa@kernel.org