linux-stable.git/kernel/bpf, branch v5.10.9

bpf: Save correct stopping point in file seq iteration

2021-01-19T17:27:28+00:00

[ Upstream commit 69ca310f34168eae0ada434796bfc22fb4a0fa26 ]

On some systems, some variant of the following splat is
repeatedly seen.  The common factor in all traces seems
to be the entry point to task_file_seq_next().  With the
patch, all warnings go away.

    rcu: INFO: rcu_sched self-detected stall on CPU
    rcu: \x0926-....: (20992 ticks this GP) idle=d7e/1/0x4000000000000002 softirq=81556231/81556231 fqs=4876
    \x09(t=21033 jiffies g=159148529 q=223125)
    NMI backtrace for cpu 26
    CPU: 26 PID: 2015853 Comm: bpftool Kdump: loaded Not tainted 5.6.13-0_fbk4_3876_gd8d1f9bf80bb #1
    Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A12 10/08/2018
    Call Trace:
     
     dump_stack+0x50/0x70
     nmi_cpu_backtrace.cold.6+0x13/0x50
     ? lapic_can_unplug_cpu.cold.30+0x40/0x40
     nmi_trigger_cpumask_backtrace+0xba/0xca
     rcu_dump_cpu_stacks+0x99/0xc7
     rcu_sched_clock_irq.cold.90+0x1b4/0x3aa
     ? tick_sched_do_timer+0x60/0x60
     update_process_times+0x24/0x50
     tick_sched_timer+0x37/0x70
     __hrtimer_run_queues+0xfe/0x270
     hrtimer_interrupt+0xf4/0x210
     smp_apic_timer_interrupt+0x5e/0x120
     apic_timer_interrupt+0xf/0x20
     
    RIP: 0010:get_pid_task+0x38/0x80
    Code: 89 f6 48 8d 44 f7 08 48 8b 00 48 85 c0 74 2b 48 83 c6 55 48 c1 e6 04 48 29 f0 74 19 48 8d 78 20 ba 01 00 00 00 f0 0f c1 50 20 <85> d2 74 27 78 11 83 c2 01 78 0c 48 83 c4 08 c3 31 c0 48 83 c4 08
    RSP: 0018:ffffc9000d293dc8 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13
    RAX: ffff888637c05600 RBX: ffffc9000d293e0c RCX: 0000000000000000
    RDX: 0000000000000001 RSI: 0000000000000550 RDI: ffff888637c05620
    RBP: ffffffff8284eb80 R08: ffff88831341d300 R09: ffff88822ffd8248
    R10: ffff88822ffd82d0 R11: 00000000003a93c0 R12: 0000000000000001
    R13: 00000000ffffffff R14: ffff88831341d300 R15: 0000000000000000
     ? find_ge_pid+0x1b/0x20
     task_seq_get_next+0x52/0xc0
     task_file_seq_get_next+0x159/0x220
     task_file_seq_next+0x4f/0xa0
     bpf_seq_read+0x159/0x390
     vfs_read+0x8a/0x140
     ksys_read+0x59/0xd0
     do_syscall_64+0x42/0x110
     entry_SYSCALL_64_after_hwframe+0x44/0xa9
    RIP: 0033:0x7f95ae73e76e
    Code: Bad RIP value.
    RSP: 002b:00007ffc02c1dbf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
    RAX: ffffffffffffffda RBX: 000000000170faa0 RCX: 00007f95ae73e76e
    RDX: 0000000000001000 RSI: 00007ffc02c1dc30 RDI: 0000000000000007
    RBP: 00007ffc02c1ec70 R08: 0000000000000005 R09: 0000000000000006
    R10: fffffffffffff20b R11: 0000000000000246 R12: 00000000019112a0
    R13: 0000000000000000 R14: 0000000000000007 R15: 00000000004283c0

If unable to obtain the file structure for the current task,
proceed to the next task number after the one returned from
task_seq_get_next(), instead of the next task number from the
original iterator.

Also, save the stopping task number from task_seq_get_next()
on failure in case of restarts.

Fixes: eaaacd23910f ("bpf: Add task and task/file iterator targets")
Signed-off-by: Jonathan Lemon 
Signed-off-by: Daniel Borkmann 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20201218185032.2464558-2-jonathan.lemon@gmail.com
Signed-off-by: Sasha Levin

bpf: Simplify task_file_seq_get_next()

2021-01-19T17:27:28+00:00

[ Upstream commit 91b2db27d3ff9ad29e8b3108dfbf1e2f49fe9bd3 ]

Simplify task_file_seq_get_next() by removing two in/out arguments: task
and fstruct. Use info->task and info->files instead.

Signed-off-by: Song Liu 
Signed-off-by: Daniel Borkmann 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20201120002833.2481110-1-songliubraving@fb.com
Signed-off-by: Sasha Levin

bpf: Fix enum names for bpf_this_cpu_ptr() and bpf_per_cpu_ptr() helpers

2020-12-11T22:19:07+00:00

Remove bpf_ prefix, which causes these helpers to be reported in verifier
dump as bpf_bpf_this_cpu_ptr() and bpf_bpf_per_cpu_ptr(), respectively. Lets
fix it as long as it is still possible before UAPI freezes on these helpers.

Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()")
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann 
Signed-off-by: Linus Torvalds

bpf: Fix propagation of 32-bit signed bounds from 64-bit bounds.

2020-12-10T21:02:53+00:00

The 64-bit signed bounds should not affect 32-bit signed bounds unless the
verifier knows that upper 32-bits are either all 1s or all 0s. For example the
register with smin_value==1 doesn't mean that s32_min_value is also equal to 1,
since smax_value could be larger than 32-bit subregister can hold.
The verifier refines the smax/s32_max return value from certain helpers in
do_refine_retval_range(). Teach the verifier to recognize that smin/s32_min
value is also bounded. When both smin and smax bounds fit into 32-bit
subregister the verifier can propagate those bounds.

Fixes: 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking")
Reported-by: Jean-Philippe Brucker 
Acked-by: John Fastabend 
Signed-off-by: Alexei Starovoitov

bpf: Relax return code check for subprograms

2020-11-14T16:17:27+00:00

Currently verifier enforces return code checks for subprograms in the
same manner as it does for program entry points. This prevents returning
arbitrary scalar values from subprograms. Scalar type of returned values
is checked by btf_prepare_func_args() and hence it should be safe to
allow only scalars for now. Relax return code checks for subprograms and
allow any correct scalar values.

Fixes: 51c39bb1d5d10 (bpf: Introduce function-by-function verification)
Signed-off-by: Dmitrii Banshchikov 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20201113171756.90594-1-me@ubique.spb.ru

bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id

2020-11-11T09:50:22+00:00

The unsigned variable datasec_id is assigned a return value from the call
to check_pseudo_btf_id(), which may return negative error code.

This fixes the following coccicheck warning:

  ./kernel/bpf/verifier.c:9616:5-15: WARNING: Unsigned expression compared with zero: datasec_id > 0

Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()")
Reported-by: Tosk Robot 
Signed-off-by: Kaixu Xia 
Signed-off-by: Daniel Borkmann 
Acked-by: Andrii Nakryiko 
Acked-by: John Fastabend 
Cc: Hao Luo 
Link: https://lore.kernel.org/bpf/1605071026-25906-1-git-send-email-kaixuxia@tencent.com

bpf: Update verification logic for LSM programs

2020-11-06T21:15:21+00:00

The current logic checks if the name of the BTF type passed in
attach_btf_id starts with "bpf_lsm_", this is not sufficient as it also
allows attachment to non-LSM hooks like the very function that performs
this check, i.e. bpf_lsm_verify_prog.

In order to ensure that this verification logic allows attachment to
only LSM hooks, the LSM_HOOK definitions in lsm_hook_defs.h are used to
generate a BTF_ID set. Upon verification, the attach_btf_id of the
program being attached is checked for presence in this set.

Fixes: 9e4e01dfd325 ("bpf: lsm: Implement attach, detach and execution")
Signed-off-by: KP Singh 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20201105230651.2621917-1-kpsingh@chromium.org

bpf: Zero-fill re-used per-cpu map element

2020-11-06T03:55:57+00:00

Zero-fill element values for all other cpus than current, just as
when not using prealloc. This is the only way the bpf program can
ensure known initial values for all cpus ('onallcpus' cannot be
set when coming from the bpf program).

The scenario is: bpf program inserts some elements in a per-cpu
map, then deletes some (or userspace does). When later adding
new elements using bpf_map_update_elem(), the bpf program can
only set the value of the new elements for the current cpu.
When prealloc is enabled, previously deleted elements are re-used.
Without the fix, values for other cpus remain whatever they were
when the re-used entry was previously freed.

A selftest is added to validate correct operation in above
scenario as well as in case of LRU per-cpu map element re-use.

Fixes: 6c9059817432 ("bpf: pre-allocate hash map elements")
Signed-off-by: David Verbeiren 
Signed-off-by: Alexei Starovoitov 
Acked-by: Matthieu Baerts 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20201104112332.15191-1-david.verbeiren@tessares.net

bpf: BPF_PRELOAD depends on BPF_SYSCALL

2020-11-06T02:49:29+00:00

Fix build error when BPF_SYSCALL is not set/enabled but BPF_PRELOAD is
by making BPF_PRELOAD depend on BPF_SYSCALL.

ERROR: modpost: "bpf_preload_ops" [kernel/bpf/preload/bpf_preload.ko] undefined!

Reported-by: kernel test robot 
Reported-by: Randy Dunlap 
Signed-off-by: Randy Dunlap 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20201105195109.26232-1-rdunlap@infradead.org

bpf: Don't rely on GCC attribute((optimize)) to disable GCSE

2020-10-30T03:01:46+00:00

Commit 3193c0836 ("bpf: Disable GCC -fgcse optimization for
___bpf_prog_run()") introduced a __no_fgcse macro that expands to a
function scope __attribute__((optimize("-fno-gcse"))), to disable a
GCC specific optimization that was causing trouble on x86 builds, and
was not expected to have any positive effect in the first place.

However, as the GCC manual documents, __attribute__((optimize))
is not for production use, and results in all other optimization
options to be forgotten for the function in question. This can
cause all kinds of trouble, but in one particular reported case,
it causes -fno-asynchronous-unwind-tables to be disregarded,
resulting in .eh_frame info to be emitted for the function.

This reverts commit 3193c0836, and instead, it disables the -fgcse
optimization for the entire source file, but only when building for
X86 using GCC with CONFIG_BPF_JIT_ALWAYS_ON disabled. Note that the
original commit states that CONFIG_RETPOLINE=n triggers the issue,
whereas CONFIG_RETPOLINE=y performs better without the optimization,
so it is kept disabled in both cases.

Fixes: 3193c0836f20 ("bpf: Disable GCC -fgcse optimization for ___bpf_prog_run()")
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Alexei Starovoitov 
Tested-by: Geert Uytterhoeven 
Reviewed-by: Nick Desaulniers 
Link: https://lore.kernel.org/lkml/CAMuHMdUg0WJHEcq6to0-eODpXPOywLot6UD2=GFHpzoj_hCoBQ@mail.gmail.com/
Link: https://lore.kernel.org/bpf/20201028171506.15682-2-ardb@kernel.org