| Message ID | 20240608-hid_bpf_struct_ops-v3-15-6ac6ade58329@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | HID: convert HID-BPF into using bpf_struct_ops | expand |
On Sat, Jun 8, 2024 at 2:01 AM Benjamin Tissoires <bentiss@kernel.org> wrote: > > The idea is to provide a list of stucts and their editable fields. > > Currently no functional changes are introduced here, we will add some > more writeable fields in the next patch. > > Signed-off-by: Benjamin Tissoires <bentiss@kernel.org> > > --- > > changes in v3: > - rewrote WRITE_RANGE macro to not deal with offset from the caller side > > new in v2 > --- > drivers/hid/bpf/hid_bpf_struct_ops.c | 91 +++++++++++++++++++++++++++--------- > 1 file changed, 69 insertions(+), 22 deletions(-) > > diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c > index 056d05d96962..b14eccb121e0 100644 > --- a/drivers/hid/bpf/hid_bpf_struct_ops.c > +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c > @@ -16,6 +16,7 @@ > #include <linux/hid_bpf.h> > #include <linux/init.h> > #include <linux/module.h> > +#include <linux/stddef.h> > #include <linux/workqueue.h> > #include "hid_bpf_dispatch.h" > > @@ -52,40 +53,86 @@ static int hid_bpf_ops_check_member(const struct btf_type *t, > return 0; > } > > +struct hid_bpf_offset_write_range { > + const char *struct_name; > + u32 struct_length; > + u32 start; > + u32 end; > +}; > + > static int hid_bpf_ops_btf_struct_access(struct bpf_verifier_log *log, > const struct bpf_reg_state *reg, > int off, int size) > { > - const struct btf_type *state; > - const struct btf_type *t; > - s32 type_id; > +#define WRITE_RANGE(_name, _field, _is_string) \ > + { \ > + .struct_name = #_name, \ > + .struct_length = sizeof(struct _name), \ > + .start = offsetof(struct _name, _field), \ > + .end = offsetofend(struct _name, _field) - !!(_is_string), so it works because char name[128]; had last byte as zero before prog writes into it (in addition to potentially having earlier 0 bytes), so the string is guaranteed to be null-terminated regardless of what prog writes into it. Right? Overall: Acked-by: Alexei Starovoitov <ast@kernel.org>
On Jun 10 2024, Alexei Starovoitov wrote: > On Sat, Jun 8, 2024 at 2:01 AM Benjamin Tissoires <bentiss@kernel.org> wrote: > > > > The idea is to provide a list of stucts and their editable fields. > > > > Currently no functional changes are introduced here, we will add some > > more writeable fields in the next patch. > > > > Signed-off-by: Benjamin Tissoires <bentiss@kernel.org> > > > > --- > > > > changes in v3: > > - rewrote WRITE_RANGE macro to not deal with offset from the caller side > > > > new in v2 > > --- > > drivers/hid/bpf/hid_bpf_struct_ops.c | 91 +++++++++++++++++++++++++++--------- > > 1 file changed, 69 insertions(+), 22 deletions(-) > > > > diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c > > index 056d05d96962..b14eccb121e0 100644 > > --- a/drivers/hid/bpf/hid_bpf_struct_ops.c > > +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c > > @@ -16,6 +16,7 @@ > > #include <linux/hid_bpf.h> > > #include <linux/init.h> > > #include <linux/module.h> > > +#include <linux/stddef.h> > > #include <linux/workqueue.h> > > #include "hid_bpf_dispatch.h" > > > > @@ -52,40 +53,86 @@ static int hid_bpf_ops_check_member(const struct btf_type *t, > > return 0; > > } > > > > +struct hid_bpf_offset_write_range { > > + const char *struct_name; > > + u32 struct_length; > > + u32 start; > > + u32 end; > > +}; > > + > > static int hid_bpf_ops_btf_struct_access(struct bpf_verifier_log *log, > > const struct bpf_reg_state *reg, > > int off, int size) > > { > > - const struct btf_type *state; > > - const struct btf_type *t; > > - s32 type_id; > > +#define WRITE_RANGE(_name, _field, _is_string) \ > > + { \ > > + .struct_name = #_name, \ > > + .struct_length = sizeof(struct _name), \ > > + .start = offsetof(struct _name, _field), \ > > + .end = offsetofend(struct _name, _field) - !!(_is_string), > > so it works because char name[128]; had last byte as zero > before prog writes into it (in addition to potentially having > earlier 0 bytes), so the string is guaranteed > to be null-terminated regardless of what prog writes into it. > Right? Yeah, struct hid_device is created through hid_allocate_device(), which does a kzalloc. Then all operations are supposedly safe in the current transport layers, so the last byte should always be \0. > > Overall: > Acked-by: Alexei Starovoitov <ast@kernel.org> Thanks a lot. I might send a v4 or not depending if I get other reviews, but I'll make sure to take your nitpick in 3/16 into account (cast kdata/udate in the beginning of the function to make the lines shorter and less verbose). Cheers, Benjamin
diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c index 056d05d96962..b14eccb121e0 100644 --- a/drivers/hid/bpf/hid_bpf_struct_ops.c +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c @@ -16,6 +16,7 @@ #include <linux/hid_bpf.h> #include <linux/init.h> #include <linux/module.h> +#include <linux/stddef.h> #include <linux/workqueue.h> #include "hid_bpf_dispatch.h" @@ -52,40 +53,86 @@ static int hid_bpf_ops_check_member(const struct btf_type *t, return 0; } +struct hid_bpf_offset_write_range { + const char *struct_name; + u32 struct_length; + u32 start; + u32 end; +}; + static int hid_bpf_ops_btf_struct_access(struct bpf_verifier_log *log, const struct bpf_reg_state *reg, int off, int size) { - const struct btf_type *state; - const struct btf_type *t; - s32 type_id; +#define WRITE_RANGE(_name, _field, _is_string) \ + { \ + .struct_name = #_name, \ + .struct_length = sizeof(struct _name), \ + .start = offsetof(struct _name, _field), \ + .end = offsetofend(struct _name, _field) - !!(_is_string), \ + } - type_id = btf_find_by_name_kind(reg->btf, "hid_bpf_ctx", - BTF_KIND_STRUCT); - if (type_id < 0) - return -EINVAL; + const struct hid_bpf_offset_write_range write_ranges[] = { + WRITE_RANGE(hid_bpf_ctx, retval, false), + }; +#undef WRITE_RANGE + const struct btf_type *state = NULL; + const struct btf_type *t; + const char *cur = NULL; + int i; t = btf_type_by_id(reg->btf, reg->btf_id); - state = btf_type_by_id(reg->btf, type_id); - if (t != state) { - bpf_log(log, "only access to hid_bpf_ctx is supported\n"); - return -EACCES; - } - /* out-of-bound access in hid_bpf_ctx */ - if (off + size > sizeof(struct hid_bpf_ctx)) { - bpf_log(log, "write access at off %d with size %d\n", off, size); - return -EACCES; + for (i = 0; i < ARRAY_SIZE(write_ranges); i++) { + const struct hid_bpf_offset_write_range *write_range = &write_ranges[i]; + s32 type_id; + + /* we already found a writeable struct, but there is a + * new one, let's break the loop. + */ + if (t == state && write_range->struct_name != cur) + break; + + /* new struct to look for */ + if (write_range->struct_name != cur) { + type_id = btf_find_by_name_kind(reg->btf, write_range->struct_name, + BTF_KIND_STRUCT); + if (type_id < 0) + return -EINVAL; + + state = btf_type_by_id(reg->btf, type_id); + } + + /* this is not the struct we are looking for */ + if (t != state) { + cur = write_range->struct_name; + continue; + } + + /* first time we see this struct, check for out of bounds */ + if (cur != write_range->struct_name && + off + size > write_range->struct_length) { + bpf_log(log, "write access for struct %s at off %d with size %d\n", + write_range->struct_name, off, size); + return -EACCES; + } + + /* now check if we are in our boundaries */ + if (off >= write_range->start && off + size <= write_range->end) + return NOT_INIT; + + cur = write_range->struct_name; } - if (off < offsetof(struct hid_bpf_ctx, retval)) { + + if (t != state) + bpf_log(log, "write access to this struct is not supported\n"); + else bpf_log(log, - "write access at off %d with size %d on read-only part of hid_bpf_ctx\n", - off, size); - return -EACCES; - } + "write access at off %d with size %d on read-only part of %s\n", + off, size, cur); - return NOT_INIT; + return -EACCES; } static const struct bpf_verifier_ops hid_bpf_verifier_ops = {
The idea is to provide a list of stucts and their editable fields. Currently no functional changes are introduced here, we will add some more writeable fields in the next patch. Signed-off-by: Benjamin Tissoires <bentiss@kernel.org> --- changes in v3: - rewrote WRITE_RANGE macro to not deal with offset from the caller side new in v2 --- drivers/hid/bpf/hid_bpf_struct_ops.c | 91 +++++++++++++++++++++++++++--------- 1 file changed, 69 insertions(+), 22 deletions(-)