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selftests/bpf: Add test cases for narrowing fill

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The previous commit allowed to preserve boundaries and track IDs of
scalars on narrowing fills. Add test cases for that pattern.

Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240127175237.526726-5-maxtram95@gmail.com
This commit is contained in:
Maxim Mikityanskiy 2024-01-27 19:52:35 +02:00 committed by Andrii Nakryiko
parent c1e6148cb4
commit 067313a85c
1 changed files with 111 additions and 0 deletions
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111
tools/testing/selftests/bpf/progs/verifier_spill_fill.c
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@ -979,4 +979,115 @@ l0_%=: r0 = 0; \
: __clobber_all);
}
SEC("xdp")
__description("32-bit fill after 64-bit spill")
__success __retval(0)
__naked void fill_32bit_after_spill_64bit(void)
{
asm volatile(" \
/* Randomize the upper 32 bits. */ \
call %[bpf_get_prandom_u32]; \
r0 <<= 32; \
/* 64-bit spill r0 to stack. */ \
*(u64*)(r10 - 8) = r0; \
/* 32-bit fill r0 from stack. */ \
"
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
"r0 = *(u32*)(r10 - 8);"
#else
"r0 = *(u32*)(r10 - 4);"
#endif
" \
/* Boundary check on r0 with predetermined result. */\
if r0 == 0 goto l0_%=; \
/* Dead branch: the verifier should prune it. Do an invalid memory\
* access if the verifier follows it. \
*/ \
r0 = *(u64*)(r9 + 0); \
l0_%=: exit; \
" :
: __imm(bpf_get_prandom_u32)
: __clobber_all);
}
SEC("xdp")
__description("32-bit fill after 64-bit spill of 32-bit value should preserve ID")
__success __retval(0)
__naked void fill_32bit_after_spill_64bit_preserve_id(void)
{
asm volatile (" \
/* Randomize the lower 32 bits. */ \
call %[bpf_get_prandom_u32]; \
w0 &= 0xffffffff; \
/* 64-bit spill r0 to stack - should assign an ID. */\
*(u64*)(r10 - 8) = r0; \
/* 32-bit fill r1 from stack - should preserve the ID. */\
"
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
"r1 = *(u32*)(r10 - 8);"
#else
"r1 = *(u32*)(r10 - 4);"
#endif
" \
/* Compare r1 with another register to trigger find_equal_scalars. */\
r2 = 0; \
if r1 != r2 goto l0_%=; \
/* The result of this comparison is predefined. */\
if r0 == r2 goto l0_%=; \
/* Dead branch: the verifier should prune it. Do an invalid memory\
* access if the verifier follows it. \
*/ \
r0 = *(u64*)(r9 + 0); \
exit; \
l0_%=: r0 = 0; \
exit; \
" :
: __imm(bpf_get_prandom_u32)
: __clobber_all);
}
SEC("xdp")
__description("32-bit fill after 64-bit spill should clear ID")
__failure __msg("math between ctx pointer and 4294967295 is not allowed")
__naked void fill_32bit_after_spill_64bit_clear_id(void)
{
asm volatile (" \
r6 = r1; \
/* Roll one bit to force the verifier to track both branches. */\
call %[bpf_get_prandom_u32]; \
r0 &= 0x8; \
/* Put a large number into r1. */ \
r1 = 0xffffffff; \
r1 <<= 32; \
r1 += r0; \
/* 64-bit spill r1 to stack - should assign an ID. */\
*(u64*)(r10 - 8) = r1; \
/* 32-bit fill r2 from stack - should clear the ID. */\
"
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
"r2 = *(u32*)(r10 - 8);"
#else
"r2 = *(u32*)(r10 - 4);"
#endif
" \
/* Compare r2 with another register to trigger find_equal_scalars.\
* Having one random bit is important here, otherwise the verifier cuts\
* the corners. If the ID was mistakenly preserved on fill, this would\
* cause the verifier to think that r1 is also equal to zero in one of\
* the branches, and equal to eight on the other branch.\
*/ \
r3 = 0; \
if r2 != r3 goto l0_%=; \
l0_%=: r1 >>= 32; \
/* The verifier shouldn't propagate r2's range to r1, so it should\
* still remember r1 = 0xffffffff and reject the below.\
*/ \
r6 += r1; \
r0 = *(u32*)(r6 + 0); \
exit; \
" :
: __imm(bpf_get_prandom_u32)
: __clobber_all);
}
char _license[] SEC("license") = "GPL";