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bpf, docs: Reformat BPF maps page to be more readable #1238

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Pull request for series with
subject: bpf, docs: Reformat BPF maps page to be more readable
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=684832

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Master branch: d31ada3
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=684832
version: 1

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Master branch: de9c8d8
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=684832
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Master branch: 721ef9e
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Master branch: 2e00cd1
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Master branch: e94e0a2
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Master branch: 62c69e8
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Master branch: 62c69e8
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Master branch: 62c69e8
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Master branch: 62c69e8
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Master branch: 04a8f9d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=684832
version: 1

Kernel Patches Daemon and others added 2 commits October 19, 2022 17:11
adding ci files
3c98b51
@donaldh
bpf, docs: Reformat BPF maps page to be more readable
b7240c8 
Add a more complete introduction, with links to man pages.
Move toctree of map types above usage notes.
Format usage notes to improve readability.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=684832 irrelevant now. Closing PR.

@kernel-patches-bot kernel-patches-bot deleted the series/684832=>bpf-next branch October 21, 2022 02:14
kernel-patches-daemon-bpf-rc bot pushed a commit that referenced this pull request Jul 1, 2025
@YuKuai-huawei @akpm00
lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()
df831e9 
While testing null_blk with configfs, echo 0 > poll_queues will trigger
following panic:

BUG: kernel NULL pointer dereference, address: 0000000000000010
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 27 UID: 0 PID: 920 Comm: bash Not tainted 6.15.0-02023-gadbdb95c8696-dirty #1238 PREEMPT(undef)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014
RIP: 0010:__bitmap_or+0x48/0x70
Call Trace:
 <TASK>
 __group_cpus_evenly+0x822/0x8c0
 group_cpus_evenly+0x2d9/0x490
 blk_mq_map_queues+0x1e/0x110
 null_map_queues+0xc9/0x170 [null_blk]
 blk_mq_update_queue_map+0xdb/0x160
 blk_mq_update_nr_hw_queues+0x22b/0x560
 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk]
 nullb_device_poll_queues_store+0xa4/0x130 [null_blk]
 configfs_write_iter+0x109/0x1d0
 vfs_write+0x26e/0x6f0
 ksys_write+0x79/0x180
 __x64_sys_write+0x1d/0x30
 x64_sys_call+0x45c4/0x45f0
 do_syscall_64+0xa5/0x240
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Root cause is that numgrps is set to 0, and ZERO_SIZE_PTR is returned from
kcalloc(), and later ZERO_SIZE_PTR will be deferenced.

Fix the problem by checking numgrps first in group_cpus_evenly(), and
return NULL directly if numgrps is zero.

[yukuai3@huawei.com: also fix the non-SMP version]
  Link: https://lkml.kernel.org/r/20250620010958.1265984-1-yukuai1@huaweicloud.com
Link: https://lkml.kernel.org/r/20250619132655.3318883-1-yukuai1@huaweicloud.com
Fixes: 6a6dcae ("blk-mq: Build default queue map via group_cpus_evenly()")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Cc: ErKun Yang <yangerkun@huawei.com>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: "zhangyi (F)" <yi.zhang@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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