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bpf: derive smin32/smax32 from umin32/umax32 bounds

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All the logic that applies to u64 vs s64, equally applies for u32 vs s32
relationships (just taken in a smaller 32-bit numeric space). So do the
same deduction of smin32/smax32 from umin32/umax32, if we can.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231102033759.2541186-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-11-01 20:37:46 -07:00 committed by Alexei Starovoitov
parent 93f7378734
commit d540517990
1 changed files with 7 additions and 0 deletions
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7
kernel/bpf/verifier.c
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@ -2324,6 +2324,13 @@ static void __update_reg_bounds(struct bpf_reg_state *reg)
/* Uses signed min/max values to inform unsigned, and vice-versa */
static void __reg32_deduce_bounds(struct bpf_reg_state *reg)
{
/* if u32 range forms a valid s32 range (due to matching sign bit),
* try to learn from that
*/
if ((s32)reg->u32_min_value <= (s32)reg->u32_max_value) {
reg->s32_min_value = max_t(s32, reg->s32_min_value, reg->u32_min_value);
reg->s32_max_value = min_t(s32, reg->s32_max_value, reg->u32_max_value);
}
/* Learn sign from signed bounds.
* If we cannot cross the sign boundary, then signed and unsigned bounds
* are the same, so combine. This works even in the negative case, e.g.