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authorGianluca Borello <g.borello@gmail.com>2017-11-22 18:32:54 +0000
committerDaniel Borkmann <daniel@iogearbox.net>2017-11-22 21:40:54 +0100
commiteb33f2cca49ec49a1b893b5af546e7c042ca6365 (patch)
tree0a3aad9face780bd56482c236c5f968bf4ea6dcd /kernel
parentdb1ac4964fa172803a0fea83033cd35d380a8a77 (diff)
bpf: remove explicit handling of 0 for arg2 in bpf_probe_read
Commit 9c019e2bc4b2 ("bpf: change helper bpf_probe_read arg2 type to ARG_CONST_SIZE_OR_ZERO") changed arg2 type to ARG_CONST_SIZE_OR_ZERO to simplify writing bpf programs by taking advantage of the new semantics introduced for ARG_CONST_SIZE_OR_ZERO which allows <!NULL, 0> arguments. In order to prevent the helper from actually passing a NULL pointer to probe_kernel_read, which can happen when <NULL, 0> is passed to the helper, the commit also introduced an explicit check against size == 0. After the recent introduction of the ARG_PTR_TO_MEM_OR_NULL type, bpf_probe_read can not receive a pair of <NULL, 0> arguments anymore, thus the check is not needed anymore and can be removed, since probe_kernel_read can correctly handle a <!NULL, 0> call. This also fixes the semantics of the helper before it gets officially released and bpf programs start relying on this check. Fixes: 9c019e2bc4b2 ("bpf: change helper bpf_probe_read arg2 type to ARG_CONST_SIZE_OR_ZERO") Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/bpf_trace.c6
1 files changed, 1 insertions, 5 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a5580c670866..728909f7951c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -78,16 +78,12 @@ EXPORT_SYMBOL_GPL(trace_call_bpf);
BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
{
- int ret = 0;
-
- if (unlikely(size == 0))
- goto out;
+ int ret;
ret = probe_kernel_read(dst, unsafe_ptr, size);
if (unlikely(ret < 0))
memset(dst, 0, size);
- out:
return ret;
}

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