Re: [Linux-kernel-mentees] [PATCH v3] bpf: Fix NULL pointer dereference in __btf_resolve_helper_id()
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2020-07-15 21:07:27
Also in:
bpf, lkml, netdev
On 7/14/20 8:09 PM, Peilin Ye wrote:
Prevent __btf_resolve_helper_id() from dereferencing `btf_vmlinux`
as NULL. This patch fixes the following syzbot bug:
https://syzkaller.appspot.com/bug?id=f823224ada908fa5c207902a5a62065e53ca0fcc
Reported-by: syzbot+ee09bda7017345f1fbe6@syzkaller.appspotmail.com
Signed-off-by: Peilin Ye <redacted>
Looks good, applied, thanks! As far as I can tell all the other occurrences are
gated behind btf_parse_vmlinux() where we also init struct_opts, etc.
So for bpf-next this would then end up looking like ...
int btf_resolve_helper_id(struct bpf_verifier_log *log,
const struct bpf_func_proto *fn, int arg)
{
int id;
if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID)
return -EINVAL;
id = fn->btf_id[arg];
if (!id || !btf_vmlinux || id > btf_vmlinux->nr_types)
return -EINVAL;
return id;
}
quoted hunk ↗ jump to hunk
--- Sorry, I got the link wrong. Thank you for pointing that out. Change in v3: - Fix incorrect syzbot dashboard link. Change in v2: - Split NULL and IS_ERR cases. kernel/bpf/btf.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 30721f2c2d10..092116a311f4 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c@@ -4088,6 +4088,11 @@ static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, const char *tname, *sym; u32 btf_id, i; + if (!btf_vmlinux) { + bpf_log(log, "btf_vmlinux doesn't exist\n"); + return -EINVAL; + } + if (IS_ERR(btf_vmlinux)) { bpf_log(log, "btf_vmlinux is malformed\n"); return -EINVAL;
_______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees