32bit bounds and 64bit bounds are updated separately in
adjust_scalar_min_max_vals() currently, let them learn from each other to
get more tight bounds tracking. Similar operation can be found in
reg_set_min_max().
Before:
func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
0: (b7) r0 = 0 ; R0_w=0
1: (b7) r1 = 0 ; R1_w=0
2: (87) r1 = -r1 ; R1_w=scalar()
3: (87) r1 = -r1 ; R1_w=scalar()
4: (c7) r1 s>>= 63 ; R1_w=scalar(smin=-1,smax=0)
5: (07) r1 += 2 ; R1_w=scalar(umin=1,umax=2,var_off=(0x0; 0xffffffff)) <--- [*]
6: (95) exit
It can be seen that even if the 64bit bounds is clear here, the 32bit
bounds is still in the state of 'UNKNOWN'.
After:
func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
0: (b7) r0 = 0 ; R0_w=0
1: (b7) r1 = 0 ; R1_w=0
2: (87) r1 = -r1 ; R1_w=scalar()
3: (87) r1 = -r1 ; R1_w=scalar()
4: (c7) r1 s>>= 63 ; R1_w=scalar(smin=-1,smax=0)
5: (07) r1 += 2 ; R1_w=scalar(umin=1,umax=2,var_off=(0x0; 0x3)) <--- [*]
6: (95) exit
Fixes: 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking")
Signed-off-by: Youlin Li <liulin063@xxxxxxxxx>
---
kernel/bpf/verifier.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0efbac0fd126..888aa50fbdc0 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8934,10 +8934,13 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
break;
}
- /* ALU32 ops are zero extended into 64bit register */
- if (alu32)
+ if (alu32) {
+ /* ALU32 ops are zero extended into 64bit register */
zext_32_to_64(dst_reg);
- reg_bounds_sync(dst_reg);
+ __reg_combine_32_into_64(dst_reg);
+ } else {
+ __reg_combine_64_into_32(dst_reg);
+ }
return 0;
}
--
2.25.1
