From: Levi Zim <rsworkt...@outlook.com>
This patch add a helper function bpf_probe_read_kernel_dynptr:
long bpf_probe_read_kernel_dynptr(const struct bpf_dynptr *dst,
u32 offset, u32 size, const void *unsafe_ptr, u64 flags);
It is useful for reading variable-length data from kernel memory into
dynptr.
Link:
https://lore.kernel.org/bpf/meyp282mb2312cfce5f7712fde313215ac6...@meyp282mb2312.ausp282.prod.outlook.com/
Signed-off-by: Levi Zim <rsworkt...@outlook.com>
---
include/linux/bpf.h | 2 ++
include/uapi/linux/bpf.h | 16 ++++++++++++++++
kernel/bpf/helpers.c | 8 ++++++--
kernel/trace/bpf_trace.c | 42 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 66 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index
f3f50e29d63929acaf12c81f8356173f1f5e154b..9d5ae8b4b7d82c4523bf0ab041d4b76bf134a106
100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1323,6 +1323,8 @@ u32 __bpf_dynptr_size(const struct bpf_dynptr_kern *ptr);
const void *__bpf_dynptr_data(const struct bpf_dynptr_kern *ptr, u32 len);
void *__bpf_dynptr_data_rw(const struct bpf_dynptr_kern *ptr, u32 len);
bool __bpf_dynptr_is_rdonly(const struct bpf_dynptr_kern *ptr);
+int bpf_dynptr_check_off_len(const struct bpf_dynptr_kern *ptr, u32 offset,
u32 len);
+enum bpf_dynptr_type bpf_dynptr_get_type(const struct bpf_dynptr_kern *ptr);
#ifdef CONFIG_BPF_JIT
int bpf_trampoline_link_prog(struct bpf_tramp_link *link,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index
2acf9b33637174bd16b1d12ccc6410c5f55a7ea9..2e08a59527ecf56732ea14ac34446b5eb25b5690
100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5805,6 +5805,21 @@ union bpf_attr {
* 0 on success.
*
* **-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * long bpf_probe_read_kernel_dynptr(const struct bpf_dynptr *dst, u32 offset,
u32 size, const void *unsafe_ptr, u64 flags)
+ * Description
+ * Safely attempt to read *size* bytes from kernel space address
+ * *unsafe_ptr* and store the data in *dst* starting from *offset*.
+ * *flags* is currently unused.
+ * Return
+ * 0 on success.
+ *
+ * **-E2BIG** if *offset* + *len* exceeds the length of *src*'s
data
+ *
+ * **-EINVAL** if *src* is an invalid dynptr or doesn't support
this
+ * support this helper, or if *flags* is not 0.
+ *
+ * Or other negative errors on failure reading kernel memory.
*/
#define ___BPF_FUNC_MAPPER(FN, ctx...) \
FN(unspec, 0, ##ctx) \
@@ -6019,6 +6034,7 @@ union bpf_attr {
FN(user_ringbuf_drain, 209, ##ctx) \
FN(cgrp_storage_get, 210, ##ctx) \
FN(cgrp_storage_delete, 211, ##ctx) \
+ FN(probe_read_kernel_dynptr, 212, ##ctx) \
/* */
/* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index
f27ce162427ab4040d2e2d2eb84a883fe57de59e..a736dc9e7be98571103ba404420be0da4dac4fbe
100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1678,7 +1678,7 @@ static void bpf_dynptr_set_type(struct bpf_dynptr_kern
*ptr, enum bpf_dynptr_typ
ptr->size |= type << DYNPTR_TYPE_SHIFT;
}
-static enum bpf_dynptr_type bpf_dynptr_get_type(const struct bpf_dynptr_kern
*ptr)
+enum bpf_dynptr_type bpf_dynptr_get_type(const struct bpf_dynptr_kern *ptr)
{
return (ptr->size & ~(DYNPTR_RDONLY_BIT)) >> DYNPTR_TYPE_SHIFT;
}
@@ -1714,7 +1714,7 @@ void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr)
memset(ptr, 0, sizeof(*ptr));
}
-static int bpf_dynptr_check_off_len(const struct bpf_dynptr_kern *ptr, u32
offset, u32 len)
+int bpf_dynptr_check_off_len(const struct bpf_dynptr_kern *ptr, u32 offset,
u32 len)
{
u32 size = __bpf_dynptr_size(ptr);
@@ -1900,6 +1900,7 @@ const struct bpf_func_proto bpf_probe_read_user_proto
__weak;
const struct bpf_func_proto bpf_probe_read_user_str_proto __weak;
const struct bpf_func_proto bpf_probe_read_kernel_proto __weak;
const struct bpf_func_proto bpf_probe_read_kernel_str_proto __weak;
+const struct bpf_func_proto bpf_probe_read_kernel_dynptr_proto __weak;
const struct bpf_func_proto bpf_task_pt_regs_proto __weak;
const struct bpf_func_proto *
@@ -2031,6 +2032,9 @@ bpf_base_func_proto(enum bpf_func_id func_id, const
struct bpf_prog *prog)
case BPF_FUNC_probe_read_kernel:
return security_locked_down(LOCKDOWN_BPF_READ_KERNEL) < 0 ?
NULL : &bpf_probe_read_kernel_proto;
+ case BPF_FUNC_probe_read_kernel_dynptr:
+ return security_locked_down(LOCKDOWN_BPF_READ_KERNEL) < 0 ?
+ NULL : &bpf_probe_read_kernel_dynptr_proto;
case BPF_FUNC_probe_read_user_str:
return &bpf_probe_read_user_str_proto;
case BPF_FUNC_probe_read_kernel_str:
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index
adc947587eb8132ebbd54778d2db937b3b8861de..75c9d1e8d04c3b8930ae81345f5586756ce8b5ec
100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -248,6 +248,48 @@ const struct bpf_func_proto bpf_probe_read_kernel_proto = {
.arg3_type = ARG_ANYTHING,
};
+BPF_CALL_5(bpf_probe_read_kernel_dynptr, const struct bpf_dynptr_kern *, dst,
+ u32, offset, u32, size, void *, unsafe_ptr, u64, flags)
+{
+ enum bpf_dynptr_type type;
+ int err;
+
+ if (!dst->data || __bpf_dynptr_is_rdonly(dst))
+ return -EINVAL;
+
+ err = bpf_dynptr_check_off_len(dst, offset, size);
+ if (err)
+ return err;
+
+ type = bpf_dynptr_get_type(dst);
+
+ switch (type) {
+ case BPF_DYNPTR_TYPE_LOCAL:
+ case BPF_DYNPTR_TYPE_RINGBUF:
+ if (flags)
+ return -EINVAL;
+ return bpf_probe_read_kernel_common(dst->data + dst->offset +
offset,
+ size, unsafe_ptr);
+ case BPF_DYNPTR_TYPE_SKB:
+ case BPF_DYNPTR_TYPE_XDP:
+ return -EINVAL;
+ default:
+ WARN_ONCE(true, "%s: unknown dynptr type %d\n", __func__, type);
+ return -EFAULT;
+ }
+}
+
+const struct bpf_func_proto bpf_probe_read_kernel_dynptr_proto = {
+ .func = bpf_probe_read_kernel_dynptr,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_DYNPTR | MEM_RDONLY,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_ANYTHING,
+ .arg5_type = ARG_ANYTHING,
+};
+
static __always_inline int
bpf_probe_read_kernel_str_common(void *dst, u32 size, const void *unsafe_ptr)
{
--
2.48.1
