diff options
author | Daniel Borkmann <daniel@iogearbox.net> | 2017-01-15 03:34:25 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-01-16 22:41:42 +0300 |
commit | 2d071c643f1cd15a24172de4b5b7ae2adb93abbb (patch) | |
tree | 31fa22a277b92984067d77bb6d2f1edaae1d2adf /kernel | |
parent | 019ec0032e821a7262995af0c81b242dc7e55c9f (diff) | |
download | linux-2d071c643f1cd15a24172de4b5b7ae2adb93abbb.tar.xz |
bpf, trace: make ctx access checks more robust
Make sure that ctx cannot potentially be accessed oob by asserting
explicitly that ctx access size into pt_regs for BPF_PROG_TYPE_KPROBE
programs must be within limits. In case some 32bit archs have pt_regs
not being a multiple of 8, then BPF_DW access could cause such access.
BPF_PROG_TYPE_KPROBE progs don't have a ctx conversion function since
there's no extra mapping needed. kprobe_prog_is_valid_access() didn't
enforce sizeof(long) as the only allowed access size, since LLVM can
generate non BPF_W/BPF_DW access to regs from time to time.
For BPF_PROG_TYPE_TRACEPOINT we don't have a ctx conversion either, so
add a BUILD_BUG_ON() check to make sure that BPF_DW access will not be
a similar issue in future (ctx works on event buffer as opposed to
pt_regs there).
Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/trace/bpf_trace.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 1860e7f1e5a8..c22a961d1a42 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -459,6 +459,13 @@ static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type return false; if (off % size != 0) return false; + /* + * Assertion for 32 bit to make sure last 8 byte access + * (BPF_DW) to the last 4 byte member is disallowed. + */ + if (off + size > sizeof(struct pt_regs)) + return false; + return true; } @@ -540,6 +547,8 @@ static bool tp_prog_is_valid_access(int off, int size, enum bpf_access_type type return false; if (off % size != 0) return false; + + BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(__u64)); return true; } |