diff options
| -rw-r--r-- | include/linux/filter.h | 2 | ||||
| -rw-r--r-- | include/uapi/linux/bpf.h | 22 | ||||
| -rw-r--r-- | kernel/bpf/cgroup.c | 65 |
3 files changed, 88 insertions, 1 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index a17732057880..f254ff92819f 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1182,6 +1182,8 @@ struct bpf_sock_ops_kern { struct bpf_sysctl_kern { struct ctl_table_header *head; struct ctl_table *table; + void *cur_val; + size_t cur_len; int write; }; diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 9c8a2f3ccb9b..063543afa359 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2522,6 +2522,25 @@ union bpf_attr { * * **-E2BIG** if the buffer wasn't big enough (*buf* will contain * truncated name in this case). + * + * int bpf_sysctl_get_current_value(struct bpf_sysctl *ctx, char *buf, size_t buf_len) + * Description + * Get current value of sysctl as it is presented in /proc/sys + * (incl. newline, etc), and copy it as a string into provided + * by program buffer *buf* of size *buf_len*. + * + * The whole value is copied, no matter what file position user + * space issued e.g. sys_read at. + * + * The buffer is always NUL terminated, unless it's zero-sized. + * Return + * Number of character copied (not including the trailing NUL). + * + * **-E2BIG** if the buffer wasn't big enough (*buf* will contain + * truncated name in this case). + * + * **-EINVAL** if current value was unavailable, e.g. because + * sysctl is uninitialized and read returns -EIO for it. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -2625,7 +2644,8 @@ union bpf_attr { FN(get_listener_sock), \ FN(skc_lookup_tcp), \ FN(tcp_check_syncookie), \ - FN(sysctl_get_name), + FN(sysctl_get_name), \ + FN(sysctl_get_current_value), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index a68387043244..c6b2cf29a54b 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -794,15 +794,37 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head, .head = head, .table = table, .write = write, + .cur_val = NULL, + .cur_len = PAGE_SIZE, }; struct cgroup *cgrp; int ret; + ctx.cur_val = kmalloc_track_caller(ctx.cur_len, GFP_KERNEL); + if (ctx.cur_val) { + mm_segment_t old_fs; + loff_t pos = 0; + + old_fs = get_fs(); + set_fs(KERNEL_DS); + if (table->proc_handler(table, 0, (void __user *)ctx.cur_val, + &ctx.cur_len, &pos)) { + /* Let BPF program decide how to proceed. */ + ctx.cur_len = 0; + } + set_fs(old_fs); + } else { + /* Let BPF program decide how to proceed. */ + ctx.cur_len = 0; + } + rcu_read_lock(); cgrp = task_dfl_cgroup(current); ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx, BPF_PROG_RUN); rcu_read_unlock(); + kfree(ctx.cur_val); + return ret == 1 ? 0 : -EPERM; } EXPORT_SYMBOL(__cgroup_bpf_run_filter_sysctl); @@ -869,12 +891,55 @@ static const struct bpf_func_proto bpf_sysctl_get_name_proto = { .arg4_type = ARG_ANYTHING, }; +static int copy_sysctl_value(char *dst, size_t dst_len, char *src, + size_t src_len) +{ + if (!dst) + return -EINVAL; + + if (!dst_len) + return -E2BIG; + + if (!src || !src_len) { + memset(dst, 0, dst_len); + return -EINVAL; + } + + memcpy(dst, src, min(dst_len, src_len)); + + if (dst_len > src_len) { + memset(dst + src_len, '\0', dst_len - src_len); + return src_len; + } + + dst[dst_len - 1] = '\0'; + + return -E2BIG; +} + +BPF_CALL_3(bpf_sysctl_get_current_value, struct bpf_sysctl_kern *, ctx, + char *, buf, size_t, buf_len) +{ + return copy_sysctl_value(buf, buf_len, ctx->cur_val, ctx->cur_len); +} + +static const struct bpf_func_proto bpf_sysctl_get_current_value_proto = { + .func = bpf_sysctl_get_current_value, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_PTR_TO_UNINIT_MEM, + .arg3_type = ARG_CONST_SIZE, +}; + static const struct bpf_func_proto * sysctl_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { switch (func_id) { case BPF_FUNC_sysctl_get_name: return &bpf_sysctl_get_name_proto; + case BPF_FUNC_sysctl_get_current_value: + return &bpf_sysctl_get_current_value_proto; default: return cgroup_base_func_proto(func_id, prog); } |