32 bit range overflow#11298
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Same as in __reg64_deduce_bounds(), refine s32/u32 ranges in __reg32_deduce_bounds() in the following situations: 0 U32_MAX | [xxxxxxxxxxxxxx u32 range xxxxxxxxxxxxxx] | |----------------------------|----------------------------| |xxxxx s32 range xxxxxxxxx] [xxxxxxx| 0 S32_MAX S32_MIN -1 0 U32_MAX | [xxxxxxxxxxxxxx u32 range xxxxxxxxxxxxxx] | |----------------------------|----------------------------| |xxxxxxxxx] [xxxxxxxxxxxx s32 range | 0 S32_MAX S32_MIN -1 This helps for e.g. consider the following program: call %[bpf_get_prandom_u32]; w0 &= 0xffffffff; if w0 < 0x3 goto 1f; // on fall-through u32 range [3..U32_MAX] if w0 s> 0x1 goto 1f; // on fall-through s32 range [S32_MIN..1] if w0 s< 0x0 goto 1f; // range can be narrowed to [S32_MIN..-1] r10 = 0; 1: ...; The reg_bounds.c selftest is updated to incorporate identical logic, refinement based on non-overflowing range halves: ((x ∩ [0, smax]) ∩ (y ∩ [0, smax])) ∪ ((x ∩ [smin,-1]) ∩ (y ∩ [smin,-1])) Reported-by: Andrea Righi <arighi@nvidia.com> Reported-by: Emil Tsalapatis <emil@etsalapatis.com> Closes: https://lore.kernel.org/bpf/aakqucg4vcujVwif@gpd4/T/ Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
… boundary Two test cases for signed/unsigned 32-bit bounds refinement when s32 range crosses the sign boundary: - s32 range [S32_MIN..1] overlapping with u32 range [3..U32_MAX], s32 range tail before sign boundary overlaps with u32 range. - s32 range [-3..5] overlapping with u32 range [0..S32_MIN+3], s32 range head after the sign boundary overlaps with u32 range. This covers both branches added in the __reg32_deduce_bounds(). Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
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