| Message ID | 20210226190908.115706-1-iii@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [v3,bpf-next] selftests/bpf: Use the last page in test_snprintf_btf on s390 | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 9 maintainers not CCed: netdev@vger.kernel.org shuah@kernel.org kpsingh@kernel.org linux-kselftest@vger.kernel.org songliubraving@fb.com kafai@fb.com john.fastabend@gmail.com alan.maguire@oracle.com andrii@kernel.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 27 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
| netdev/stable | success | Stable not CCed |
On 2/26/21 11:09 AM, Ilya Leoshkevich wrote: > test_snprintf_btf fails on s390, because NULL points to a readable > struct lowcore there. Fix by using the last page instead. > > Error message example: > > printing 0000000000000000 should generate error, got (361) > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > --- > > v1: https://lore.kernel.org/bpf/20210226135923.114211-1-iii@linux.ibm.com/ > v1 -> v2: Yonghong suggested to add the pointer value to the error > message. > I've noticed that I've been passing BADPTR as flags, therefore > the fix worked only by accident. Put it into p.ptr where it > belongs. > > v2: https://lore.kernel.org/bpf/20210226182014.115347-1-iii@linux.ibm.com/ > v2 -> v3: Heiko mentioned that using _REGION1_SIZE is not future-proof. > We had a private discussion and came to the conclusion that > the the last page is good enough. Heiko, could you ack the patch if it is okay? Thanks! > > .../testing/selftests/bpf/progs/netif_receive_skb.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c > index 6b670039ea67..c3669967067e 100644 > --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c > +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c > @@ -16,6 +16,13 @@ bool skip = false; > #define STRSIZE 2048 > #define EXPECTED_STRSIZE 256 > > +#if defined(bpf_target_s390) > +/* NULL points to a readable struct lowcore on s390, so take the last page */ > +#define BADPTR ((void *)0xFFFFFFFFFFFFF000ULL) > +#else > +#define BADPTR 0 > +#endif > + > #ifndef ARRAY_SIZE > #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) > #endif > @@ -113,11 +120,11 @@ int BPF_PROG(trace_netif_receive_skb, struct sk_buff *skb) > } > > /* Check invalid ptr value */ > - p.ptr = 0; > + p.ptr = BADPTR; > __ret = bpf_snprintf_btf(str, STRSIZE, &p, sizeof(p), 0); > if (__ret >= 0) { > - bpf_printk("printing NULL should generate error, got (%d)", > - __ret); > + bpf_printk("printing %p should generate error, got (%d)", > + BADPTR, __ret); From https://www.kernel.org/doc/Documentation/printk-formats.txt: Pointers printed without a specifier extension (i.e unadorned %p) are hashed to give a unique identifier without leaking kernel addresses to user space. On 64 bit machines the first 32 bits are zeroed. If you _really_ want the address see %px below. I think it is okay to use %px here. > ret = -ERANGE; > } > >
On Fri, 2021-02-26 at 19:47 -0800, Yonghong Song wrote: > > > On 2/26/21 11:09 AM, Ilya Leoshkevich wrote: > > test_snprintf_btf fails on s390, because NULL points to a readable > > struct lowcore there. Fix by using the last page instead. > > > > Error message example: > > > > printing 0000000000000000 should generate error, got (361) > > > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > > --- > > > > v1: > > https://lore.kernel.org/bpf/20210226135923.114211-1-iii@linux.ibm.com/ > > v1 -> v2: Yonghong suggested to add the pointer value to the error > > message. > > I've noticed that I've been passing BADPTR as flags, > > therefore > > the fix worked only by accident. Put it into p.ptr where > > it > > belongs. > > > > v2: > > https://lore.kernel.org/bpf/20210226182014.115347-1-iii@linux.ibm.com/ > > v2 -> v3: Heiko mentioned that using _REGION1_SIZE is not future- > > proof. > > We had a private discussion and came to the conclusion > > that > > the the last page is good enough. > > Heiko, could you ack the patch if it is okay? Thanks! > > > > > .../testing/selftests/bpf/progs/netif_receive_skb.c | 13 > > ++++++++++--- > > 1 file changed, 10 insertions(+), 3 deletions(-) > > > > diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > b/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > index 6b670039ea67..c3669967067e 100644 > > --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > @@ -16,6 +16,13 @@ bool skip = false; > > #define STRSIZE 2048 > > #define EXPECTED_STRSIZE 256 > > > > +#if defined(bpf_target_s390) > > +/* NULL points to a readable struct lowcore on s390, so take the > > last page */ > > +#define BADPTR ((void *)0xFFFFFFFFFFFFF000ULL) > > +#else > > +#define BADPTR 0 > > +#endif > > + > > #ifndef ARRAY_SIZE > > #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) > > #endif > > @@ -113,11 +120,11 @@ int BPF_PROG(trace_netif_receive_skb, struct > > sk_buff *skb) > > } > > > > /* Check invalid ptr value */ > > - p.ptr = 0; > > + p.ptr = BADPTR; > > __ret = bpf_snprintf_btf(str, STRSIZE, &p, sizeof(p), 0); > > if (__ret >= 0) { > > - bpf_printk("printing NULL should generate error, > > got (%d)", > > - __ret); > > + bpf_printk("printing %p should generate error, got > > (%d)", > > + BADPTR, __ret); > > From https://www.kernel.org/doc/Documentation/printk-formats.txt: > > Pointers printed without a specifier extension (i.e unadorned %p) are > hashed to give a unique identifier without leaking kernel addresses > to user > space. On 64 bit machines the first 32 bits are zeroed. If you > _really_ > want the address see %px below. > > I think it is okay to use %px here. I don't think bpf_trace_printk supports it, but I'll use %llx instead. [...]
On Fri, Feb 26, 2021 at 07:47:02PM -0800, Yonghong Song wrote: > > test_snprintf_btf fails on s390, because NULL points to a readable > > struct lowcore there. Fix by using the last page instead. > > > > Error message example: > > > > printing 0000000000000000 should generate error, got (361) > > > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > > --- > > v2 -> v3: Heiko mentioned that using _REGION1_SIZE is not future-proof. > > We had a private discussion and came to the conclusion that > > the the last page is good enough. > > Heiko, could you ack the patch if it is okay? Thanks! Yes, sure. Acked-by: Heiko Carstens <hca@linux.ibm.com>
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 6b670039ea67..c3669967067e 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -16,6 +16,13 @@ bool skip = false; #define STRSIZE 2048 #define EXPECTED_STRSIZE 256 +#if defined(bpf_target_s390) +/* NULL points to a readable struct lowcore on s390, so take the last page */ +#define BADPTR ((void *)0xFFFFFFFFFFFFF000ULL) +#else +#define BADPTR 0 +#endif + #ifndef ARRAY_SIZE #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) #endif @@ -113,11 +120,11 @@ int BPF_PROG(trace_netif_receive_skb, struct sk_buff *skb) } /* Check invalid ptr value */ - p.ptr = 0; + p.ptr = BADPTR; __ret = bpf_snprintf_btf(str, STRSIZE, &p, sizeof(p), 0); if (__ret >= 0) { - bpf_printk("printing NULL should generate error, got (%d)", - __ret); + bpf_printk("printing %p should generate error, got (%d)", + BADPTR, __ret); ret = -ERANGE; }
test_snprintf_btf fails on s390, because NULL points to a readable struct lowcore there. Fix by using the last page instead. Error message example: printing 0000000000000000 should generate error, got (361) Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- v1: https://lore.kernel.org/bpf/20210226135923.114211-1-iii@linux.ibm.com/ v1 -> v2: Yonghong suggested to add the pointer value to the error message. I've noticed that I've been passing BADPTR as flags, therefore the fix worked only by accident. Put it into p.ptr where it belongs. v2: https://lore.kernel.org/bpf/20210226182014.115347-1-iii@linux.ibm.com/ v2 -> v3: Heiko mentioned that using _REGION1_SIZE is not future-proof. We had a private discussion and came to the conclusion that the the last page is good enough. .../testing/selftests/bpf/progs/netif_receive_skb.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)