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| author |   Jann Horn <jannh@google.com> | 2017-12-22 19:12:35 +0100 |
|---|---|---|
| committer |   Daniel Borkmann <daniel@iogearbox.net> | 2017-12-27 18:35:07 +0100 |
| commit | 6b80ad299208b44ba33cb6df80bdaa3f63cf03e2 (patch) | |
| tree | 0b2677f632475bd3350400a565b51bf6231e16c1 /tools/testing | |
| parent | bpf: fix stacksafe exploration when comparing states (diff) | |
| download | linux-dev-6b80ad299208b44ba33cb6df80bdaa3f63cf03e2.tar.xz linux-dev-6b80ad299208b44ba33cb6df80bdaa3f63cf03e2.zip | |
bpf: selftest for late caller stack size increase
This checks that it is not possible to bypass the total stack size check in
update_stack_depth() by calling a function that uses a large amount of
stack memory *before* using a large amount of stack memory in the caller.
Currently, the first added testcase causes a rejection as expected, but
the second testcase is (AFAICS incorrectly) accepted:
[...]
#483/p calls: stack overflow using two frames (post-call access) FAIL
Unexpected success to load!
0: (85) call pc+2
caller:
R10=fp0,call_-1
callee:
frame1: R1=ctx(id=0,off=0,imm=0) R10=fp0,call_0
3: (72) *(u8 *)(r10 -300) = 0
4: (b7) r0 = 0
5: (95) exit
returning from callee:
frame1: R0_w=inv0 R1=ctx(id=0,off=0,imm=0) R10=fp0,call_0
to caller at 1:
R0_w=inv0 R10=fp0,call_-1
from 5 to 1: R0=inv0 R10=fp0,call_-1
1: (72) *(u8 *)(r10 -300) = 0
2: (95) exit
processed 6 insns, stack depth 300+300
[...]
Summary: 704 PASSED, 1 FAILED
AFAICS the JIT-generated code for the second testcase shows that this
really causes the stack pointer to be decremented by 300+300:
first function:
00000000 55 push rbp
00000001 4889E5 mov rbp,rsp
00000004 4881EC58010000 sub rsp,0x158
0000000B 4883ED28 sub rbp,byte +0x28
[...]
00000025 E89AB3AFE5 call 0xffffffffe5afb3c4
0000002A C685D4FEFFFF00 mov byte [rbp-0x12c],0x0
[...]
00000041 4883C528 add rbp,byte +0x28
00000045 C9 leave
00000046 C3 ret
second function:
00000000 55 push rbp
00000001 4889E5 mov rbp,rsp
00000004 4881EC58010000 sub rsp,0x158
0000000B 4883ED28 sub rbp,byte +0x28
[...]
00000025 C685D4FEFFFF00 mov byte [rbp-0x12c],0x0
[...]
0000003E 4883C528 add rbp,byte +0x28
00000042 C9 leave
00000043 C3 ret
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'tools/testing')
| -rw-r--r-- | tools/testing/selftests/bpf/test_verifier.c | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 5e79515d10c5..41dcc7dbba42 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -8730,6 +8730,40 @@ static struct bpf_test tests[] = { .result = ACCEPT, }, { + "calls: stack overflow using two frames (pre-call access)", + .insns = { + /* prog 1 */ + BPF_ST_MEM(BPF_B, BPF_REG_10, -300, 0), + BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, 1), + BPF_EXIT_INSN(), + + /* prog 2 */ + BPF_ST_MEM(BPF_B, BPF_REG_10, -300, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .prog_type = BPF_PROG_TYPE_XDP, + .errstr = "combined stack size", + .result = REJECT, + }, + { + "calls: stack overflow using two frames (post-call access)", + .insns = { + /* prog 1 */ + BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, 2), + BPF_ST_MEM(BPF_B, BPF_REG_10, -300, 0), + BPF_EXIT_INSN(), + + /* prog 2 */ + BPF_ST_MEM(BPF_B, BPF_REG_10, -300, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .prog_type = BPF_PROG_TYPE_XDP, + .errstr = "combined stack size", + .result = REJECT, + }, + { "calls: spill into caller stack frame", .insns = { BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), |