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bpf: Fix a buffer out-of-bound access when filling raw_tp link_info 

Commit f2e10bff16 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
added link query for raw_tp. One of fields in link_info is to
fill a user buffer with tp_name. The Scurrent checking only
declares "ulen && !ubuf" as invalid. So "!ulen && ubuf" will be
valid. Later on, we do "copy_to_user(ubuf, tp_name, ulen - 1)" which
may overwrite user memory incorrectly.

This patch fixed the problem by disallowing "!ulen && ubuf" case as well.

Fixes: f2e10bff16 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200821191054.714731-1-yhs@fb.com
zero-sugar-mainline-defconfig
Yonghong Song 2020-08-21 12:10:54 -07:00 committed by Alexei Starovoitov
parent 99408c422d
commit b474959d5a
1 changed files with 1 additions and 1 deletions
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kernel/bpf/syscall.c
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@ -2634,7 +2634,7 @@ static int bpf_raw_tp_link_fill_link_info(const struct bpf_link *link,
u32 ulen = info->raw_tracepoint.tp_name_len;
size_t tp_len = strlen(tp_name);
if (ulen && !ubuf)
if (!ulen ^ !ubuf)
return -EINVAL;
info->raw_tracepoint.tp_name_len = tp_len + 1;