path: root/kernel
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authorGianluca Borello <g.borello@gmail.com>2017-11-22 18:32:53 +0000
committerDaniel Borkmann <daniel@iogearbox.net>2017-11-22 21:40:54 +0100
commitdb1ac4964fa172803a0fea83033cd35d380a8a77 (patch)
tree6b44959b16ee233dbe875e77b84783a927514fde /kernel
parentf1a8b8e3d98b0b3d1d88d119f52cc85d05ab3189 (diff)
bpf: introduce ARG_PTR_TO_MEM_OR_NULL
With the current ARG_PTR_TO_MEM/ARG_PTR_TO_UNINIT_MEM semantics, an helper argument can be NULL when the next argument type is ARG_CONST_SIZE_OR_ZERO and the verifier can prove the value of this next argument is 0. However, most helpers are just interested in handling <!NULL, 0>, so forcing them to deal with <NULL, 0> makes the implementation of those helpers more complicated for no apparent benefits, requiring them to explicitly handle those corner cases with checks that bpf programs could start relying upon, preventing the possibility of removing them later. Solve this by making ARG_PTR_TO_MEM/ARG_PTR_TO_UNINIT_MEM never accept NULL even when ARG_CONST_SIZE_OR_ZERO is set, and introduce a new argument type ARG_PTR_TO_MEM_OR_NULL to explicitly deal with the NULL case. Currently, the only helper that needs this is bpf_csum_diff_proto(), so change arg1 and arg3 to this new type as well. Also add a new battery of tests that explicitly test the !ARG_PTR_TO_MEM_OR_NULL combination: all the current ones testing the various <NULL, 0> variations are focused on bpf_csum_diff, so cover also other helpers. Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index dd54d20ace2f..308b0638ec5d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1384,13 +1384,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_MEM ||
+ arg_type == ARG_PTR_TO_MEM_OR_NULL ||
arg_type == ARG_PTR_TO_UNINIT_MEM) {
expected_type = PTR_TO_STACK;
/* One exception here. In case function allows for NULL to be
* passed in as argument, it's a SCALAR_VALUE type. Final test
* happens during stack boundary checking.
- if (register_is_null(*reg))
+ if (register_is_null(*reg) &&
+ arg_type == ARG_PTR_TO_MEM_OR_NULL)
/* final test in check_stack_boundary() */;
else if (!type_is_pkt_pointer(type) &&
type != PTR_TO_MAP_VALUE &&

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