diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 766695491bc5..181b6dc9ef7a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -15301,21 +15301,17 @@ static void __scalar64_min_max_lsh(struct bpf_reg_state *dst_reg, u64 umin_val, u64 umax_val) { /* Special case <<32 because it is a common compiler pattern to sign - * extend subreg by doing <<32 s>>32. In this case if 32bit bounds are - * positive we know this shift will also be positive so we can track - * bounds correctly. Otherwise we lose all sign bit information except - * what we can pick up from var_off. Perhaps we can generalize this - * later to shifts of any length. + * extend subreg by doing <<32 s>>32. smin/smax assignments are correct + * because s32 bounds don't flip sign when shifting to the left by + * 32bits. */ - if (umin_val == 32 && umax_val == 32 && dst_reg->s32_max_value >= 0) + if (umin_val == 32 && umax_val == 32) { dst_reg->smax_value = (s64)dst_reg->s32_max_value << 32; - else - dst_reg->smax_value = S64_MAX; - - if (umin_val == 32 && umax_val == 32 && dst_reg->s32_min_value >= 0) dst_reg->smin_value = (s64)dst_reg->s32_min_value << 32; - else + } else { + dst_reg->smax_value = S64_MAX; dst_reg->smin_value = S64_MIN; + } /* If we might shift our top bit out, then we know nothing */ if (dst_reg->umax_value > 1ULL << (63 - umax_val)) { diff --git a/tools/testing/selftests/bpf/progs/verifier_subreg.c b/tools/testing/selftests/bpf/progs/verifier_subreg.c index 8613ea160dcd..55e56697dbc4 100644 --- a/tools/testing/selftests/bpf/progs/verifier_subreg.c +++ b/tools/testing/selftests/bpf/progs/verifier_subreg.c @@ -531,6 +531,76 @@ __naked void arsh32_imm_zero_extend_check(void) : __clobber_all); } +SEC("socket") +__description("arsh32 imm sign positive extend check") +__success __retval(0) +__naked void arsh32_imm_sign_extend_positive_check(void) +__log_level(2) +__msg("2: (57) r6 &= 4095 ; R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4095,var_off=(0x0; 0xfff))") +__msg("3: (67) r6 <<= 32 ; R6=scalar(smin=smin32=0,smax=umax=0xfff00000000,smax32=umax32=0,var_off=(0x0; 0xfff00000000))") +__msg("4: (c7) r6 s>>= 32 ; R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4095,var_off=(0x0; 0xfff))") + +{ + asm volatile (" \ + call %[bpf_get_prandom_u32]; \ + r6 = r0; \ + r6 &= 4095; \ + r6 <<= 32; \ + r6 s>>= 32; \ + r0 = 0; \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +SEC("socket") +__description("arsh32 imm sign negative extend check") +__success __retval(0) +__naked void arsh32_imm_sign_extend_negative_check(void) +__log_level(2) +__msg("3: (17) r6 -= 4095 ; R6=scalar(smin=smin32=-4095,smax=smax32=0)") +__msg("4: (67) r6 <<= 32 ; R6=scalar(smin=0xfffff00100000000,smax=smax32=umax32=0,umax=0xffffffff00000000,smin32=0,var_off=(0x0; 0xffffffff00000000))") +__msg("5: (c7) r6 s>>= 32 ; R6=scalar(smin=smin32=-4095,smax=smax32=0)") + +{ + asm volatile (" \ + call %[bpf_get_prandom_u32]; \ + r6 = r0; \ + r6 &= 4095; \ + r6 -= 4095; \ + r6 <<= 32; \ + r6 s>>= 32; \ + r0 = 0; \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +SEC("socket") +__description("arsh32 imm sign extend check") +__success __retval(0) +__naked void arsh32_imm_sign_extend_check(void) +__log_level(2) +__msg("3: (17) r6 -= 2047 ; R6=scalar(smin=smin32=-2047,smax=smax32=2048)") +__msg("4: (67) r6 <<= 32 ; R6=scalar(smin=0xfffff80100000000,smax=0x80000000000,umax=0xffffffff00000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xffffffff00000000))") +__msg("5: (c7) r6 s>>= 32 ; R6=scalar(smin=smin32=-2047,smax=smax32=2048)") +{ + asm volatile (" \ + call %[bpf_get_prandom_u32]; \ + r6 = r0; \ + r6 &= 4095; \ + r6 -= 2047; \ + r6 <<= 32; \ + r6 s>>= 32; \ + r0 = 0; \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + SEC("socket") __description("end16 (to_le) reg zero extend check") __success __success_unpriv __retval(0)