Merge branch 'fixes for bpf map iterator'

Hou Tao says:

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From: Hou Tao <houtao1@huawei.com>

Hi,

The patchset constitues three fixes for bpf map iterator:

(1) patch 1~4: fix user-after-free during reading map iterator fd
It is possible when both the corresponding link fd and map fd are
closed bfore reading the iterator fd. I had squashed these four patches
into one, but it was not friendly for stable backport, so I break these
fixes into four single patches in the end. Patch 7 is its testing patch.

(2) patch 5: fix invalidity check for values in sk local storage map
Patch 8 adds two tests for it.

(3) patch 6: reject sleepable program for non-resched map iterator
Patch 9 add a test for it.

Please check the individual patches for more details. And comments are
always welcome.

Regards,
Tao

Changes since v2:
* patch 1~6: update commit messages (from Yonghong & Martin)
* patch 7: add more detailed comments (from Yonghong)
* patch 8: use NULL directly instead of (void *)0

v1: https://lore.kernel.org/bpf/20220806074019.2756957-1-houtao@huaweicloud.com
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Signed-off-by: Alexei Starovoitov <ast@kernel.org>