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tools, bpftool: Fix struct_ops command invalid pointer free 

In commit 65c9362859 ("bpftool: Add struct_ops support") a new
type of command named struct_ops has been added. This command requires
a kernel with CONFIG_DEBUG_INFO_BTF=y set and for retrieving BTF info
in bpftool, the helper get_btf_vmlinux() is used.

When running this command on kernel without BTF debug info, this will
lead to 'btf_vmlinux' variable being an invalid(error) pointer. And by
this, btf_free() causes a segfault when executing 'bpftool struct_ops'.

This commit adds pointer validation with IS_ERR not to free invalid
pointer, and this will fix the segfault issue.

Fixes: 65c9362859 ("bpftool: Add struct_ops support")
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200410020612.2930667-1-danieltimlee@gmail.com
This commit is contained in:
Daniel T. Lee 2020-04-10 11:06:12 +09:00 committed by Daniel Borkmann
parent 642c165470
commit 96b2eb6e77
1 changed files with 3 additions and 1 deletions
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4
tools/bpf/bpftool/struct_ops.c
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@ -591,6 +591,8 @@ int do_struct_ops(int argc, char **argv)
err = cmd_select(cmds, argc, argv, do_help);
btf__free(btf_vmlinux);
if (!IS_ERR(btf_vmlinux))
btf__free(btf_vmlinux);
return err;
}