bpf: Fix propagation of signed bounds from 64-bit min/max into 32-bit.

Alexei Starovoitov · anakryiko · commit 388e2c0b9783 · 2021-11-01T18:05:12.000-07:00
Similar to unsigned bounds propagation fix signed bounds. The 'Fixes' tag is a hint. There is no security bug here. The verifier was too conservative. Fixes: 3f50f13 ("bpf: Verifier, do explicit ALU32 bounds tracking") Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20211101222153.78759-2-alexei.starovoitov@gmail.com
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
@@ -1420,7 +1420,7 @@ static void __reg_combine_32_into_64(struct bpf_reg_state *reg)
 
 static bool __reg64_bound_s32(s64 a)
 {
-	return a > S32_MIN && a < S32_MAX;
+	return a >= S32_MIN && a <= S32_MAX;
 }
 
 static bool __reg64_bound_u32(u64 a)

Original file line number	Diff line number	Diff line change
`@@ -1420,7 +1420,7 @@ static void __reg_combine_32_into_64(struct bpf_reg_state *reg)`
`1420`	`1420`
`1421`	`1421`	`static bool __reg64_bound_s32(s64 a)`
`1422`	`1422`	`{`
`1423`		`- return a > S32_MIN && a < S32_MAX;`
	`1423`	`+ return a >= S32_MIN && a <= S32_MAX;`
`1424`	`1424`	`}`
`1425`	`1425`
`1426`	`1426`	`static bool __reg64_bound_u32(u64 a)`