On Tue, Aug 23, 2022 at 11:25:15PM +0300, Ovidiu Panait wrote:
Hi Jean-Philippe,
On 8/23/22 21:34, Jean-Philippe Brucker wrote:
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On Tue, Aug 23, 2022 at 10:31:40AM +0300, RAJESH DASARI wrote:
Sorry for the confusion, results are indeed confusing to me . If I try with git bisect I get
git bisect bad 9d6f67365d9cdb389fbdac2bb5b00e59e345930e is the first bad commit
For me bisecting points to:
(A) 7c1134c7da99 ("bpf: Verifer, adjust_scalar_min_max_vals to always call update_reg_bounds()")
This changes the BPF verifier output and (as expected) breaks the test_align selftest. That's why in the same series [1] another patch fixed test_align. In v5.4.y, that patch is:
(B) 6a9b3f0f3bad ("selftests/bpf: Fix test_align verifier log patterns")
Unfortunately commit (B) addresses multiple verifier changes, not solely (A). My guess is those changes were in series [1] and haven't been backported to v5.4. So multiple solutions:
- Partially revert (B), only keeping the changes needed by (A)
- Revert (A) and (B)
- Add the missing commits that (B) also addresses
I don't know which, I suppose it depends on the intent behind backporting (A). Ovidiu?
The intent behind backporting 7c1134c7da99 ("bpf: Verifer, adjust_scalar_min_max_vals to always call update_reg_bounds()") was to fix CVE-2021-4159.
If we revert test 11 changes brought in by 6a9b3f0f3bad ("selftests/bpf: Fix test_align verifier log patterns") backport, all test_align testcases pass on my side:
diff --git a/tools/testing/selftests/bpf/test_align.c b/tools/testing/selftests/bpf/test_align.c index c9c9bdce9d6d..4726e3eca9b2 100644 --- a/tools/testing/selftests/bpf/test_align.c +++ b/tools/testing/selftests/bpf/test_align.c @@ -580,18 +580,18 @@ static struct bpf_align_test tests[] = { /* Adding 14 makes R6 be (4n+2) */ {11, "R6_w=inv(id=0,umin_value=14,umax_value=74,var_off=(0x2; 0x7c))"}, /* Subtracting from packet pointer overflows ubounds */ - {13, "R5_w=pkt(id=1,off=0,r=8,umin_value=18446744073709551542,umax_value=18446744073709551602,var_off=(0xffffffffffffff82; 0x7c)"}, + {13, "R5_w=pkt(id=1,off=0,r=8,umin_value=18446744073709551542,umax_value=18446744073709551602,var_off=(0xffffffffffffff82; 0x7c))"}, /* New unknown value in R7 is (4n), >= 76 */ {15, "R7_w=inv(id=0,umin_value=76,umax_value=1096,var_off=(0x0; 0x7fc))"}, /* Adding it to packet pointer gives nice bounds again */ - {16, "R5_w=pkt(id=2,off=0,r=0,umin_value=2,umax_value=1082,var_off=(0x2; 0xfffffffc)"}, + {16, "R5_w=pkt(id=2,off=0,r=0,umin_value=2,umax_value=1082,var_off=(0x2; 0x7fc))"}, /* At the time the word size load is performed from R5, * its total fixed offset is NET_IP_ALIGN + reg->off (0) * which is 2. Then the variable offset is (4n+2), so * the total offset is 4-byte aligned and meets the * load's requirements. */ - {20, "R5=pkt(id=2,off=0,r=4,umin_value=2,umax_value=1082,var_off=(0x2; 0xfffffffc)"}, + {20, "R5=pkt(id=2,off=0,r=4,umin_value=2,umax_value=1082,var_off=(0x2; 0x7fc))"}, }, }, };
root@intel-x86-64:~/bpf# ./test_align Test 0: mov ... PASS Test 1: shift ... PASS Test 2: addsub ... PASS Test 3: mul ... PASS Test 4: unknown shift ... PASS Test 5: unknown mul ... PASS Test 6: packet const offset ... PASS Test 7: packet variable offset ... PASS Test 8: packet variable offset 2 ... PASS Test 9: dubious pointer arithmetic ... PASS Test 10: variable subtraction ... PASS Test 11: pointer variable subtraction ... PASS Results: 12 pass 0 fail
In any case 6098562ed9df ("selftests/bpf: Fix "dubious pointer arithmetic" test") can be reverted, I can send that once we figure out the rest.
In my testing, with [1] and [2] applied, but without [3], the following test_align selftest would still fail:
Test 9: dubious pointer arithmetic ... Failed to find match 9: R5=inv(id=0,umin_value=2,umax_value=9223372034707292158,var_off=(0x2; 0x7fffffff7ffffffc)
Right thanks for the details, so I think the cleanest is to revert [3] and partially revert [2], tests 11 and part of 9. I'll send that out
Thanks, Jean
[1] 7c1134c7da99 ("bpf: Verifer, adjust_scalar_min_max_vals to always call update_reg_bounds()") [2] 6a9b3f0f3bad ("selftests/bpf: Fix test_align verifier log patterns") [3] 6098562ed9df ("selftests/bpf: Fix "dubious pointer arithmetic" test")
Ovidiu