github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-26 16:12:59 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

bpf: Test nospec after dead stack write in helper

Browse Source 
Without the fix from the previous commit, the selftest fails:

$ ./tools/testing/selftests/bpf/vmtest.sh -- \
        ./test_progs -t verifier_unpriv
[...]
run_subtest:PASS:obj_open_mem 0 nsec
libbpf: BTF loading error: -EPERM
libbpf: Error loading .BTF into kernel: -EPERM. BTF is optional, ignoring.
libbpf: prog 'unpriv_nospec_after_helper_stack_write': BPF program load failed: -EFAULT
libbpf: prog 'unpriv_nospec_after_helper_stack_write': failed to load: -EFAULT
libbpf: failed to load object 'verifier_unpriv'
run_subtest:FAIL:unexpected_load_failure unexpected error: -14 (errno 14)
VERIFIER LOG:
=============
0: R1=ctx() R10=fp0
0: (b7) r0 = 0                        ; R0=P0
1: (55) if r0 != 0x1 goto pc+6 2: R0=Pscalar() R1=ctx() R10=fp0
2: (b7) r2 = 0                        ; R2=P0
3: (bf) r3 = r10                      ; R3=fp0 R10=fp0
4: (07) r3 += -16                     ; R3=fp-16
5: (b7) r4 = 4                        ; R4=P4
6: (b7) r5 = 0                        ; R5=P0
7: (85) call bpf_skb_load_bytes_relative#68
verifier bug: speculation barrier after jump instruction may not have the desired effect (BPF_CLASS(insn->code) == BPF_JMP || BPF_CLASS(insn->code) == BPF_JMP32)
processed 9 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
=============
[...]

The test is based on the PoC from the report.

Signed-off-by: Luis Gerhorst <luis.gerhorst@fau.de>
Reported-by: Yinhao Hu <dddddd@hust.edu.cn>
Reported-by: Kaiyan Mei <M202472210@hust.edu.cn>
Reported-by: Dongliang Mu <dzm91@hust.edu.cn>
Link: https://lore.kernel.org/bpf/7678017d-b760-4053-a2d8-a6879b0dbeeb@hust.edu.cn/
Link: https://lore.kernel.org/r/20260127115912.3026761-3-luis.gerhorst@fau.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Luis Gerhorst 2026-01-27 12:59:12 +01:00 committed by Alexei Starovoitov
parent cd3b6a3d49
commit 60d2c438c1
1 changed files with 22 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
tools/testing/selftests/bpf/progs/verifier_unpriv.c
View File

@ -950,4 +950,26 @@ l3_%=: r0 = 0; \
" ::: __clobber_all);
}
SEC("socket")
__description("unpriv: nospec after dead stack write in helper")
__success __success_unpriv
__retval(0)
/* Dead code sanitizer rewrites the call to `goto -1`. */
__naked void unpriv_dead_helper_stack_write_nospec_result(void)
{
asm volatile (" \
r0 = 0; \
if r0 != 1 goto l0_%=; \
r2 = 0; \
r3 = r10; \
r3 += -16; \
r4 = 4; \
r5 = 0; \
call %[bpf_skb_load_bytes_relative]; \
l0_%=: exit; \
" :
: __imm(bpf_skb_load_bytes_relative)
: __clobber_all);
}
char _license[] SEC("license") = "GPL";