From: Levi Zim rsworktech@outlook.com
This patch add a helper function bpf_probe_read_user_dynptr:
long bpf_probe_read_user_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 user memory into dynptr.
Signed-off-by: Levi Zim rsworktech@outlook.com --- include/uapi/linux/bpf.h | 16 ++++++++++ kernel/bpf/helpers.c | 3 ++ kernel/trace/bpf_trace.c | 76 +++++++++++++++++++++++++++++++++--------------- 3 files changed, 71 insertions(+), 24 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 2e08a59527ecf56732ea14ac34446b5eb25b5690..d7d7a9ddd5dca07ba89d81ba77101a704af3163b 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5820,6 +5820,21 @@ union bpf_attr { * support this helper, or if *flags* is not 0. * * Or other negative errors on failure reading kernel memory. + * + * long bpf_probe_read_user_dynptr(const struct bpf_dynptr *dst, u32 offset, u32 size, const void *unsafe_ptr, u64 flags) + * Description + * Safely attempt to read *size* bytes from user 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 user space memory. */ #define ___BPF_FUNC_MAPPER(FN, ctx...) \ FN(unspec, 0, ##ctx) \ @@ -6035,6 +6050,7 @@ union bpf_attr { FN(cgrp_storage_get, 210, ##ctx) \ FN(cgrp_storage_delete, 211, ##ctx) \ FN(probe_read_kernel_dynptr, 212, ##ctx) \ + FN(probe_read_user_dynptr, 213, ##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 a736dc9e7be98571103ba404420be0da4dac4fbe..ac563d09082e7c721999d7de035aabc000206a29 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1898,6 +1898,7 @@ const struct bpf_func_proto bpf_get_current_task_proto __weak; const struct bpf_func_proto bpf_get_current_task_btf_proto __weak; 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_user_dynptr_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; @@ -2029,6 +2030,8 @@ bpf_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_current_task_btf_proto; case BPF_FUNC_probe_read_user: return &bpf_probe_read_user_proto; + case BPF_FUNC_probe_read_user_dynptr: + return &bpf_probe_read_user_dynptr_proto; case BPF_FUNC_probe_read_kernel: return security_locked_down(LOCKDOWN_BPF_READ_KERNEL) < 0 ? NULL : &bpf_probe_read_kernel_proto; diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 75c9d1e8d04c3b8930ae81345f5586756ce8b5ec..d9f704c1342773c74b2414be4adfc8271d6d364d 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -181,6 +181,36 @@ bpf_probe_read_user_common(void *dst, u32 size, const void __user *unsafe_ptr) return ret; }
+static int bpf_probe_read_check_dynptr(const struct bpf_dynptr_kern *dst, + u32 offset, u32 size, 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 0; + 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; + } +} + BPF_CALL_3(bpf_probe_read_user, void *, dst, u32, size, const void __user *, unsafe_ptr) { @@ -196,6 +226,26 @@ const struct bpf_func_proto bpf_probe_read_user_proto = { .arg3_type = ARG_ANYTHING, };
+BPF_CALL_5(bpf_probe_read_user_dynptr, const struct bpf_dynptr_kern *, dst, + u32, offset, u32, size, void *, unsafe_ptr, u64, flags) +{ + int ret = bpf_probe_read_check_dynptr(dst, offset, size, flags); + + return ret ?: bpf_probe_read_user_common(dst->data + dst->offset + offset, + size, unsafe_ptr); +} + +const struct bpf_func_proto bpf_probe_read_user_dynptr_proto = { + .func = bpf_probe_read_user_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_user_str_common(void *dst, u32 size, const void __user *unsafe_ptr) @@ -251,32 +301,10 @@ const struct bpf_func_proto bpf_probe_read_kernel_proto = { 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; + int ret = bpf_probe_read_check_dynptr(dst, offset, size, flags);
- 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, + return ret ?: 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 = {