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Add tests where two packet pointers share an id and tightening one
pointer's umax from its var_off would put it less than their constant
distance from the other's umax: with an index & 0x38 capped at 50, the
base pointer keeps umax 50, so the pointer 8 bytes further on must keep
umax 58, even though its known bits allow at most 56.
These refused a valid program or accepted an out-of-bounds access before
the fix:
- check the advanced copy, load through the base: valid, was refused;
- check the base, load the byte at base + 1 through a copy advanced by
8: was accepted;
- check base + 4, load 4 bytes at base + 2 through base + 8: reads two
bytes past the checked range, was accepted;
- the same as the second with data_meta pointers checked against data:
was accepted.
These pass with and without the fix and cover nearby paths:
- subtract an unknown scalar from a checked pointer and load below it
(the range is kept across a new id);
- reach a load through two paths whose checks cover 8 and 7 bytes after
the loaded pointer; the second path must not be pruned by the first;
- spill a copy of a pointer, check the pointer, fill the copy and load
one byte past the checked range: the load is refused, and the copy
has the range of the check.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
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