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bpf: Make 32->64 bounds propagation slightly more robust

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Make the bounds propagation in __reg_assign_32_into_64() slightly more
robust and readable by aligning it similarly as we did back in the
__reg_combine_64_into_32() counterpart. Meaning, only propagate or
pessimize them as a smin/smax pair.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2021-12-15 22:28:48 +00:00
parent 3cf2b61eb0
commit e572ff80f0
1 changed files with 15 additions and 9 deletions
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24
kernel/bpf/verifier.c
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@ -1366,22 +1366,28 @@ static void __reg_bound_offset(struct bpf_reg_state *reg)
reg->var_off = tnum_or(tnum_clear_subreg(var64_off), var32_off); reg->var_off = tnum_or(tnum_clear_subreg(var64_off), var32_off);
} }
static bool __reg32_bound_s64(s32 a)
{
return a >= 0 && a <= S32_MAX;
}
static void __reg_assign_32_into_64(struct bpf_reg_state *reg) static void __reg_assign_32_into_64(struct bpf_reg_state *reg)
{ {
reg->umin_value = reg->u32_min_value; reg->umin_value = reg->u32_min_value;
reg->umax_value = reg->u32_max_value; reg->umax_value = reg->u32_max_value;
/* Attempt to pull 32-bit signed bounds into 64-bit bounds
* but must be positive otherwise set to worse case bounds /* Attempt to pull 32-bit signed bounds into 64-bit bounds but must
* and refine later from tnum. * be positive otherwise set to worse case bounds and refine later
* from tnum.
*/ */
if (reg->s32_min_value >= 0 && reg->s32_max_value >= 0) if (__reg32_bound_s64(reg->s32_min_value) &&
reg->smax_value = reg->s32_max_value; __reg32_bound_s64(reg->s32_max_value)) {
else
reg->smax_value = U32_MAX;
if (reg->s32_min_value >= 0)
reg->smin_value = reg->s32_min_value; reg->smin_value = reg->s32_min_value;
else reg->smax_value = reg->s32_max_value;
} else {
reg->smin_value = 0; reg->smin_value = 0;
reg->smax_value = U32_MAX;
}
} }
static void __reg_combine_32_into_64(struct bpf_reg_state *reg) static void __reg_combine_32_into_64(struct bpf_reg_state *reg)