55 lines
1.9 KiB
Diff
55 lines
1.9 KiB
Diff
From: "Lee, Chun-Yi" <jlee@suse.com>
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Date: Wed, 5 Apr 2017 17:40:31 +0100
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Subject: [58/62] bpf: Restrict kernel image access functions when the kernel
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is locked down
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=12c6b01166d3a94a49cf78a8bfe37fb280dd7cb6
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There are some bpf functions can be used to read kernel memory:
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bpf_probe_read, bpf_probe_write_user and bpf_trace_printk. These allow
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private keys in kernel memory (e.g. the hibernation image signing key) to
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be read by an eBPF program. Prohibit those functions when the kernel is
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locked down.
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Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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---
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kernel/trace/bpf_trace.c | 11 +++++++++++
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1 file changed, 11 insertions(+)
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diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
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index cee9802cf3e0..7fde851f207b 100644
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--- a/kernel/trace/bpf_trace.c
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+++ b/kernel/trace/bpf_trace.c
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@@ -65,6 +65,11 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
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{
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int ret;
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+ if (kernel_is_locked_down()) {
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+ memset(dst, 0, size);
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+ return -EPERM;
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+ }
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+
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ret = probe_kernel_read(dst, unsafe_ptr, size);
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if (unlikely(ret < 0))
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memset(dst, 0, size);
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@@ -84,6 +89,9 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
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BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
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u32, size)
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{
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+ if (kernel_is_locked_down())
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+ return -EPERM;
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+
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/*
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* Ensure we're in user context which is safe for the helper to
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* run. This helper has no business in a kthread.
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@@ -143,6 +151,9 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
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if (fmt[--fmt_size] != 0)
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return -EINVAL;
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+ if (kernel_is_locked_down())
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+ return __trace_printk(1, fmt, 0, 0, 0);
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+
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/* check format string for allowed specifiers */
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for (i = 0; i < fmt_size; i++) {
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if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
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