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bpf: Make use of probe_user_write in probe write helper

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Convert the bpf_probe_write_user() helper to probe_user_write() such that
writes are not attempted under KERNEL_DS anymore which is buggy as kernel
and user space pointers can have overlapping addresses. Also, given we have
the access_ok() check inside probe_user_write(), the helper doesn't need
to do it twice.

Fixes: 96ae522795 ("bpf: Add bpf_probe_write_user BPF helper to be called in tracers")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/841c461781874c07a0ee404a454c3bc0459eed30.1572649915.git.daniel@iogearbox.net
This commit is contained in:
Daniel Borkmann 2019-11-02 00:17:58 +01:00 committed by Alexei Starovoitov
parent 75a1a607bb
commit eb1b668874
1 changed files with 2 additions and 4 deletions
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6
kernel/trace/bpf_trace.c
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@ -163,7 +163,7 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
.arg3_type = ARG_ANYTHING, .arg3_type = ARG_ANYTHING,
}; };
BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src, BPF_CALL_3(bpf_probe_write_user, void __user *, unsafe_ptr, const void *, src,
u32, size) u32, size)
{ {
/* /*
@ -186,10 +186,8 @@ BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
return -EPERM; return -EPERM;
if (unlikely(!nmi_uaccess_okay())) if (unlikely(!nmi_uaccess_okay()))
return -EPERM; return -EPERM;
if (!access_ok(unsafe_ptr, size))
return -EPERM;
return probe_kernel_write(unsafe_ptr, src, size); return probe_user_write(unsafe_ptr, src, size);
} }
static const struct bpf_func_proto bpf_probe_write_user_proto = { static const struct bpf_func_proto bpf_probe_write_user_proto = {