Patch "selftests/bpf: Workaround strict bpf_lsm return value check." has been added to the 6.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    selftests/bpf: Workaround strict bpf_lsm return value check.

to the 6.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     selftests-bpf-workaround-strict-bpf_lsm-return-value.patch
and it can be found in the queue-6.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1dc1a438af7ac0336987e6d51cb8cd21497547b2
Author: Alexei Starovoitov <ast@xxxxxxxxxx>
Date:   Mon Jul 22 19:08:15 2024 -0700

    selftests/bpf: Workaround strict bpf_lsm return value check.
    
    [ Upstream commit aa8ebb270c66cea1f56a25d0f938036e91ad085a ]
    
    test_progs-no_alu32 -t libbpf_get_fd_by_id_opts
    is being rejected by the verifier with the following error
    due to compiler optimization:
    
    6: (67) r0 <<= 62                     ; R0_w=scalar(smax=0x4000000000000000,umax=0xc000000000000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xc000000000000000))
    7: (c7) r0 s>>= 63                    ; R0_w=scalar(smin=smin32=-1,smax=smax32=0)
    ;  @ test_libbpf_get_fd_by_id_opts.c:0
    8: (57) r0 &= -13                     ; R0_w=scalar(smax=0x7ffffffffffffff3,umax=0xfffffffffffffff3,smax32=0x7ffffff3,umax32=0xfffffff3,var_off=(0x0; 0xfffffffffffffff3))
    ; int BPF_PROG(check_access, struct bpf_map *map, fmode_t fmode) @ test_libbpf_get_fd_by_id_opts.c:27
    9: (95) exit
    At program exit the register R0 has smax=9223372036854775795 should have been in [-4095, 0]
    
    Workaround by adding barrier().
    Eventually the verifier will be able to recognize it.
    
    Fixes: 5d99e198be27 ("bpf, lsm: Add check for BPF LSM return value")
    Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
    Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c b/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c
index f5ac5f3e89196..568816307f712 100644
--- a/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c
+++ b/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c
@@ -31,6 +31,7 @@ int BPF_PROG(check_access, struct bpf_map *map, fmode_t fmode)
 
 	if (fmode & FMODE_WRITE)
 		return -EACCES;
+	barrier();
 
 	return 0;
 }