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bpf: Fix copy_map_value, zero_map_value

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The current offset needs to also skip over the already copied region in
addition to the size of the next field. This case manifests where there
are gaps between adjacent special fields.

It was observed that for a map value with size 48, having fields at:
off:  0, 16, 32
size: 4, 16, 16

The current code does:

memcpy(dst + 0, src + 0, 0)
memcpy(dst + 4, src + 4, 12)
memcpy(dst + 20, src + 20, 12)
memcpy(dst + 36, src + 36, 12)

With the fix, it is done correctly as:

memcpy(dst + 0, src + 0, 0)
memcpy(dst + 4, src + 4, 12)
memcpy(dst + 32, src + 32, 0)
memcpy(dst + 48, src + 48, 0)

Fixes: 4d7d7f69f4 ("bpf: Adapt copy_map_value for multiple offset case")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221114191547.1694267-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2022-11-15 00:45:24 +05:30 • committed by Alexei Starovoitov
commit e5feed0f64
1 changed files with 2 additions and 2 deletions
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