From: Levi Zim rsworktech@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/MEYP282MB2312CFCE5F7712FDE313215AC64D2@MEYP282MB... Signed-off-by: Levi Zim rsworktech@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) {