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bpf: Disallow bpf programs call prog_run command.

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The verifier cannot perform sufficient validation of bpf_attr->test.ctx_in
pointer, therefore bpf programs should not be allowed to call BPF_PROG_RUN
command from within the program.
To fix this issue split bpf_sys_bpf() bpf helper into normal kern_sys_bpf()
kernel function that can only be used by the kernel light skeleton directly.

Reported-by: YiFei Zhu <zhuyifei@google.com>
Fixes: b1d18a7574 ("bpf: Extend sys_bpf commands for bpf_syscall programs.")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2022-08-08 20:58:09 -07:00
parent aada476655
commit 86f44fcec2
2 changed files with 16 additions and 8 deletions
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20
kernel/bpf/syscall.c
View file

@ -5071,9 +5071,6 @@ static bool syscall_prog_is_valid_access(int off, int size,
BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
{
struct bpf_prog * __maybe_unused prog;
struct bpf_tramp_run_ctx __maybe_unused run_ctx;
switch (cmd) {
case BPF_MAP_CREATE:
case BPF_MAP_UPDATE_ELEM:
@ -5083,6 +5080,18 @@ BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
case BPF_LINK_CREATE:
case BPF_RAW_TRACEPOINT_OPEN:
break;
default:
return -EINVAL;
}
return __sys_bpf(cmd, KERNEL_BPFPTR(attr), attr_size);
}
int kern_sys_bpf(int cmd, union bpf_attr *attr, unsigned int size)
{
struct bpf_prog * __maybe_unused prog;
struct bpf_tramp_run_ctx __maybe_unused run_ctx;
switch (cmd) {
#ifdef CONFIG_BPF_JIT /* __bpf_prog_enter_sleepable used by trampoline and JIT */
case BPF_PROG_TEST_RUN:
if (attr->test.data_in || attr->test.data_out ||
@ -5113,11 +5122,10 @@ BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
return 0;
#endif
default:
return -EINVAL;
return ____bpf_sys_bpf(cmd, attr, size);
}
return __sys_bpf(cmd, KERNEL_BPFPTR(attr), attr_size);
}
EXPORT_SYMBOL(bpf_sys_bpf);
EXPORT_SYMBOL(kern_sys_bpf);
static const struct bpf_func_proto bpf_sys_bpf_proto = {
.func = bpf_sys_bpf,

4
tools/lib/bpf/skel_internal.h
View file

@ -66,13 +66,13 @@ struct bpf_load_and_run_opts {
const char *errstr;
};
long bpf_sys_bpf(__u32 cmd, void *attr, __u32 attr_size);
long kern_sys_bpf(__u32 cmd, void *attr, __u32 attr_size);
static inline int skel_sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr,
unsigned int size)
{
#ifdef __KERNEL__
return bpf_sys_bpf(cmd, attr, size);
return kern_sys_bpf(cmd, attr, size);
#else
return syscall(__NR_bpf, cmd, attr, size);
#endif