[PATCH 5.14 548/849] bpf: Fix propagation of signed bounds from 64-bit min/max into 32-bit.

Greg Kroah-Hartman
2021-11-15T23:07:51Z

From: Alexei Starovoitov <ast@kernel.org>

[ Upstream commit 388e2c0b978339dee9b0a81a2e546f8979e021e2 ]

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: 3f50f132d840 ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/verifier.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b9fb079559a6d..4dd9cedfc453d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1397,7 +1397,7 @@ 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)
--
2.33.0