bpf: Fix an issue in bpf_prog_test_run_xdp when page size greater than 4K

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[ Upstream commit 4fc012daf9 ]

The bpf selftest xdp_adjust_tail/xdp_adjust_frags_tail_grow failed on
arm64 with 64KB page:
   xdp_adjust_tail/xdp_adjust_frags_tail_grow:FAIL

In bpf_prog_test_run_xdp(), the xdp->frame_sz is set to 4K, but later on
when constructing frags, with 64K page size, the frag data_len could
be more than 4K. This will cause problems in bpf_xdp_frags_increase_tail().

To fix the failure, the xdp->frame_sz is set to be PAGE_SIZE so kernel
can test different page size properly. With the kernel change, the user
space and bpf prog needs adjustment. Currently, the MAX_SKB_FRAGS default
value is 17, so for 4K page, the maximum packet size will be less than 68K.
To test 64K page, a bigger maximum packet size than 68K is desired. So two
different functions are implemented for subtest xdp_adjust_frags_tail_grow.
Depending on different page size, different data input/output sizes are used
to adapt with different page size.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250612035032.2207498-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stable-dep-of: e558cca217 ("bpf, test_run: Subtract size of xdp_frame from allowed metadata size")
Signed-off-by: Sasha Levin <sashal@kernel.org>

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This commit is contained in:

Yonghong Song 2025-06-11 20:50:32 -07:00 • committed by Greg Kroah-Hartman

parent 5c647749bc

commit 202c5b915e

3 changed files with 97 additions and 9 deletions

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2

net/bpf/test_run.c

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96

tools/testing/selftests/bpf/prog_tests/xdp_adjust_tail.c

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8

tools/testing/selftests/bpf/progs/test_xdp_adjust_tail_grow.c

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