From: Andrii Nakryiko <andrii@kernel.org> mainline inclusion from mainline-5.12-rc1 commit e22d7f05e445165e58feddb4e40cc9c0f94453bc category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ------------------------------------------------- Add comments clarifying that USER variants of CO-RE reading macro are still only going to work with kernel types, defined in kernel or kernel module BTF. This should help preventing invalid use of those macro to read user-defined types (which doesn't work with CO-RE). Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20210108194408.3468860-1-andrii@kernel.org (cherry picked from commit e22d7f05e445165e58feddb4e40cc9c0f94453bc) Signed-off-by: Wang Yufen <wangyufen@huawei.com> --- tools/lib/bpf/bpf_core_read.h | 45 ++++++++++++++++++++++++++++++----- 1 file changed, 39 insertions(+), 6 deletions(-) diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h index c032f435ce35..e4aa9996a550 100644 --- a/tools/lib/bpf/bpf_core_read.h +++ b/tools/lib/bpf/bpf_core_read.h @@ -205,6 +205,7 @@ enum bpf_enum_value_kind { #define bpf_core_read(dst, sz, src) \ bpf_probe_read_kernel(dst, sz, (const void *)__builtin_preserve_access_index(src)) +/* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */ #define bpf_core_read_user(dst, sz, src) \ bpf_probe_read_user(dst, sz, (const void *)__builtin_preserve_access_index(src)) /* @@ -215,6 +216,7 @@ enum bpf_enum_value_kind { #define bpf_core_read_str(dst, sz, src) \ bpf_probe_read_kernel_str(dst, sz, (const void *)__builtin_preserve_access_index(src)) +/* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */ #define bpf_core_read_user_str(dst, sz, src) \ bpf_probe_read_user_str(dst, sz, (const void *)__builtin_preserve_access_index(src)) @@ -310,7 +312,11 @@ enum bpf_enum_value_kind { dst, (src), a, ##__VA_ARGS__) \ }) -/* Variant of BPF_CORE_READ_INTO() for reading from user-space memory */ +/* + * Variant of BPF_CORE_READ_INTO() for reading from user-space memory. + * + * NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. + */ #define BPF_CORE_READ_USER_INTO(dst, src, a, ...) ({ \ ___core_read(bpf_core_read_user, bpf_core_read_user, \ dst, (src), a, ##__VA_ARGS__) \ @@ -322,7 +328,11 @@ enum bpf_enum_value_kind { dst, (src), a, ##__VA_ARGS__) \ }) -/* Non-CO-RE variant of BPF_CORE_READ_USER_INTO() */ +/* Non-CO-RE variant of BPF_CORE_READ_USER_INTO(). + * + * As no CO-RE relocations are emitted, source types can be arbitrary and are + * not restricted to kernel types only. + */ #define BPF_PROBE_READ_USER_INTO(dst, src, a, ...) ({ \ ___core_read(bpf_probe_read_user, bpf_probe_read_user, \ dst, (src), a, ##__VA_ARGS__) \ @@ -338,7 +348,11 @@ enum bpf_enum_value_kind { dst, (src), a, ##__VA_ARGS__) \ }) -/* Variant of BPF_CORE_READ_STR_INTO() for reading from user-space memory */ +/* + * Variant of BPF_CORE_READ_STR_INTO() for reading from user-space memory. + * + * NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. + */ #define BPF_CORE_READ_USER_STR_INTO(dst, src, a, ...) ({ \ ___core_read(bpf_core_read_user_str, bpf_core_read_user, \ dst, (src), a, ##__VA_ARGS__) \ @@ -350,7 +364,12 @@ enum bpf_enum_value_kind { dst, (src), a, ##__VA_ARGS__) \ }) -/* Non-CO-RE variant of BPF_CORE_READ_USER_STR_INTO() */ +/* + * Non-CO-RE variant of BPF_CORE_READ_USER_STR_INTO(). + * + * As no CO-RE relocations are emitted, source types can be arbitrary and are + * not restricted to kernel types only. + */ #define BPF_PROBE_READ_USER_STR_INTO(dst, src, a, ...) ({ \ ___core_read(bpf_probe_read_user_str, bpf_probe_read_user, \ dst, (src), a, ##__VA_ARGS__) \ @@ -386,7 +405,16 @@ enum bpf_enum_value_kind { __r; \ }) -/* Variant of BPF_CORE_READ() for reading from user-space memory */ +/* + * Variant of BPF_CORE_READ() for reading from user-space memory. + * + * NOTE: all the source types involved are still *kernel types* and need to + * exist in kernel (or kernel module) BTF, otherwise CO-RE relocation will + * fail. Custom user types are not relocatable with CO-RE. + * The typical situation in which BPF_CORE_READ_USER() might be used is to + * read kernel UAPI types from the user-space memory passed in as a syscall + * input argument. + */ #define BPF_CORE_READ_USER(src, a, ...) ({ \ ___type((src), a, ##__VA_ARGS__) __r; \ BPF_CORE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \ @@ -400,7 +428,12 @@ enum bpf_enum_value_kind { __r; \ }) -/* Non-CO-RE variant of BPF_CORE_READ_USER() */ +/* + * Non-CO-RE variant of BPF_CORE_READ_USER(). + * + * As no CO-RE relocations are emitted, source types can be arbitrary and are + * not restricted to kernel types only. + */ #define BPF_PROBE_READ_USER(src, a, ...) ({ \ ___type((src), a, ##__VA_ARGS__) __r; \ BPF_PROBE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \ -- 2.20.1