From: Rong Tao <[email protected]> Add string concatenation kfuncs, prototype:
int bpf_strcat(char *dst, u32 dst__sz, const char *src); int bpf_strncat(char *dst, u32 dst__sz, const char *src, u32 len); This differs from the glibc library functions strcat and strncat, which, for safety reasons, require the size of the target string's memory space as a parameter. The src parameter cannot directly pass a string constant, such as "XYZ", otherwise it will throw an error "write into map forbidden". Signed-off-by: Rong Tao <[email protected]> --- kernel/bpf/helpers.c | 75 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index c18f1e16edee..85afff60365c 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -4195,6 +4195,79 @@ __bpf_kfunc int bpf_strncasestr(const char *s1__ign, const char *s2__ign, return __bpf_strnstr(s1__ign, s2__ign, len, true); } +static int __bpf_strncat(char *dst, u32 dsz, const char *src, u32 sz) +{ + int dlen = 0, slen, space, copied; + + if (sz == 0 || dsz == 0) + return -EINVAL; + + while (dlen < dsz && dst[dlen] != '\0') + dlen++; + + if (dlen >= dsz) + return -E2BIG; + + space = dsz - dlen; + + slen = bpf_strnlen(src, sz); + if (space <= slen) + return -E2BIG; + + copied = strncpy_from_kernel_nofault(dst + dlen, src, sz); + if (copied < 0) + return copied; + else if (copied == 0 || copied == 1) + return dlen; + + /* The copied character count includes '\0'. */ + return dlen + copied - 1; +} + +/** + * bpf_strcat - Append non-null bytes from a source string, and null-terminate + * the result + * @dst: Destination string. + * @dst__sz: Maximum bytes of @dst__ign, includes the trailing NUL. + * @src: Source string. + * + * Return: + * * >=0 - Length of the concatenated string. + * + * * %-EINVAL - String @dst__ign is invalid. + * * %-EFAULT - Cannot read or write one of the strings. + * * %-E2BIG - String @src__ign is too large or the remaining space in + * @dst__ign is too small. + * * %-ERANGE - One of the strings is outside of kernel address space + */ +__bpf_kfunc int bpf_strcat(char *dst, u32 dst__sz, const char *src) +{ + return __bpf_strncat(dst, dst__sz, src, dst__sz); +} + +/** + * bpf_strncat - Append non-null bytes from a source string, and null-terminate + * the result + * @dst: Destination string. + * @dst__sz: Maximum bytes of @dst__ign, includes the trailing NUL. + * @src: Source string. + * @len: the maximum number of characters to concatenate, the null terminator + * \0 of the target string @dst will also be included. + * + * Return: + * * >=0 - Length of the concatenated string. + * + * * %-EINVAL - String @dst__ign is invalid. + * * %-EFAULT - Cannot read or write one of the strings. + * * %-E2BIG - String @src__ign is too large or the remaining space in + * @dst__ign is too small. + * * %-ERANGE - One of the strings is outside of kernel address space + */ +__bpf_kfunc int bpf_strncat(char *dst, u32 dst__sz, const char *src, u32 len) +{ + return __bpf_strncat(dst, dst__sz, src, len); +} + #ifdef CONFIG_KEYS /** * bpf_lookup_user_key - lookup a key by its serial @@ -4958,6 +5031,8 @@ BTF_ID_FLAGS(func, bpf_strstr); BTF_ID_FLAGS(func, bpf_strcasestr); BTF_ID_FLAGS(func, bpf_strnstr); BTF_ID_FLAGS(func, bpf_strncasestr); +BTF_ID_FLAGS(func, bpf_strcat); +BTF_ID_FLAGS(func, bpf_strncat); #if defined(CONFIG_BPF_LSM) && defined(CONFIG_CGROUPS) BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU) #endif -- 2.55.0
