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From: Xu Kuohai <xukuohai@huaweicloud.com>
To: bpf@vger.kernel.org, linux-security-module@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
	Yonghong Song <yonghong.song@linux.dev>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Florent Revest <revest@chromium.org>,
	Brendan Jackman <jackmanb@chromium.org>,
	Paul Moore <paul@paul-moore.com>,
	James Morris <jmorris@namei.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	Khadija Kamran <kamrankhadijadj@gmail.com>,
	Casey Schaufler <casey@schaufler-ca.com>,
	Ondrej Mosnacek <omosnace@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	John Johansen <john.johansen@canonical.com>,
	Lukas Bulwahn <lukas.bulwahn@gmail.com>,
	Roberto Sassu <roberto.sassu@huawei.com>,
	Shung-Hsi Yu <shung-hsi.yu@suse.com>
Subject: [PATCH bpf-next v2 6/7] selftests/bpf: Avoid load failure for token_lsm.c
Date: Mon, 25 Mar 2024 17:56:52 +0800	[thread overview]
Message-ID: <20240325095653.1720123-7-xukuohai@huaweicloud.com> (raw)
In-Reply-To: <20240325095653.1720123-1-xukuohai@huaweicloud.com>

From: Xu Kuohai <xukuohai@huawei.com>

The compiler optimized the two bpf progs in token_lsm.c to make return
value from the bool variable in the "return -1" path, causing an
unexpected rejection:

0: R1=ctx() R10=fp0
; int BPF_PROG(bpf_token_capable, struct bpf_token *token, int cap) @ bpf_lsm.c:17
0: (b7) r6 = 0                        ; R6_w=0
; if (my_pid == 0 || my_pid != (bpf_get_current_pid_tgid() >> 32)) @ bpf_lsm.c:19
1: (18) r1 = 0xffffc9000102a000       ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5)
3: (61) r7 = *(u32 *)(r1 +0)          ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5) R7_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
4: (15) if r7 == 0x0 goto pc+11       ; R7_w=scalar(smin=umin=umin32=1,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
5: (67) r7 <<= 32                     ; R7_w=scalar(smax=0x7fffffff00000000,umax=0xffffffff00000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xffffffff00000000))
6: (c7) r7 s>>= 32                    ; R7_w=scalar(smin=0xffffffff80000000,smax=0x7fffffff)
7: (85) call bpf_get_current_pid_tgid#14      ; R0=scalar()
8: (77) r0 >>= 32                     ; R0_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
9: (5d) if r0 != r7 goto pc+6         ; R0_w=scalar(smin=smin32=0,smax=umax=umax32=0x7fffffff,var_off=(0x0; 0x7fffffff)) R7=scalar(smin=smin32=0,smax=umax=umax32=0x7fffffff,var_off=(0x0; 0x7fffffff))
; if (reject_capable) @ bpf_lsm.c:21
10: (18) r1 = 0xffffc9000102a004      ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5,off=4)
12: (71) r6 = *(u8 *)(r1 +0)          ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5,off=4) R6_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff))
;  @ bpf_lsm.c:0
13: (87) r6 = -r6                     ; R6_w=scalar()
14: (67) r6 <<= 56                    ; R6_w=scalar(smax=0x7f00000000000000,umax=0xff00000000000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xff00000000000000))
15: (c7) r6 s>>= 56                   ; R6_w=scalar(smin=smin32=-128,smax=smax32=127)
; int BPF_PROG(bpf_token_capable, struct bpf_token *token, int cap) @ bpf_lsm.c:17
16: (bf) r0 = r6                      ; R0_w=scalar(id=1,smin=smin32=-128,smax=smax32=127) R6_w=scalar(id=1,smin=smin32=-128,smax=smax32=127)
17: (95) exit
At program exit the register R0 has smin=-128 smax=127 should have been in [-4095, 0]

To avoid this failure, change the variable type from bool to int.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
---
 tools/testing/selftests/bpf/progs/token_lsm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/token_lsm.c b/tools/testing/selftests/bpf/progs/token_lsm.c
index e4d59b6ba743..a6002d073b1b 100644
--- a/tools/testing/selftests/bpf/progs/token_lsm.c
+++ b/tools/testing/selftests/bpf/progs/token_lsm.c
@@ -8,8 +8,8 @@
 char _license[] SEC("license") = "GPL";
 
 int my_pid;
-bool reject_capable;
-bool reject_cmd;
+int reject_capable;
+int reject_cmd;
 
 SEC("lsm/bpf_token_capable")
 int BPF_PROG(token_capable, struct bpf_token *token, int cap)
-- 
2.30.2


  parent reply	other threads:[~2024-03-25  9:52 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-25  9:56 [PATCH bpf-next v2 0/7] Add check for bpf lsm return value Xu Kuohai
2024-03-25  9:56 ` [PATCH bpf-next v2 1/7] bpf, lsm: Annotate lsm hook return integer with new macro LSM_RET_INT Xu Kuohai
2024-03-25  9:56 ` [PATCH bpf-next v2 2/7] bpf, lsm: Add return value range description for lsm hook Xu Kuohai
2024-04-08 17:09   ` KP Singh
2024-04-08 22:15     ` KP Singh
2024-04-10 12:30       ` Xu Kuohai
2024-03-25  9:56 ` [PATCH bpf-next v2 3/7] bpf, lsm: Add function to read lsm hook return value range Xu Kuohai
2024-03-25  9:56 ` [PATCH bpf-next v2 4/7] bpf, lsm: Check bpf lsm hook return values in verifier Xu Kuohai
2024-03-25  9:56 ` [PATCH bpf-next v2 5/7] bpf: Fix compare error in function retval_range_within Xu Kuohai
2024-03-25  9:56 ` Xu Kuohai [this message]
2024-03-25  9:56 ` [PATCH bpf-next v2 7/7] selftests/bpf: Add return value checks and corrections for failed progs Xu Kuohai
2024-04-08 21:45 ` [PATCH bpf-next v2 0/7] Add check for bpf lsm return value KP Singh
2024-04-10 12:34   ` Xu Kuohai

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