From: Kuan-Wei Chiu visitorckw@gmail.com

stable inclusion from stable-v6.6.55 commit c2d9f9a7837ab29ccae0c42252f17d436bf0a501 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB0MX4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ Upstream commit f04e2ad394e2755d0bb2d858ecb5598718bf00d5 ]

When netfilter has no entry to display, qsort is called with qsort(NULL, 0, ...). This results in undefined behavior, as UBSan reports:

net.c:827:2: runtime error: null pointer passed as argument 1, which is declared to never be null

Although the C standard does not explicitly state whether calling qsort with a NULL pointer when the size is 0 constitutes undefined behavior, Section 7.1.4 of the C standard (Use of library functions) mentions:

"Each of the following statements applies unless explicitly stated otherwise in the detailed descriptions that follow: If an argument to a function has an invalid value (such as a value outside the domain of the function, or a pointer outside the address space of the program, or a null pointer, or a pointer to non-modifiable storage when the corresponding parameter is not const-qualified) or a type (after promotion) not expected by a function with variable number of arguments, the behavior is undefined."

To avoid this, add an early return when nf_link_info is NULL to prevent calling qsort with a NULL pointer.

Signed-off-by: Kuan-Wei Chiu visitorckw@gmail.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Reviewed-by: Quentin Monnet qmo@kernel.org Link: https://lore.kernel.org/bpf/20240910150207.3179306-1-visitorckw@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Wen Zhiwei wenzhiwei@kylinos.cn --- tools/bpf/bpftool/net.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c index fd54ff436493..28e9417a5c2e 100644 --- a/tools/bpf/bpftool/net.c +++ b/tools/bpf/bpftool/net.c @@ -819,6 +819,9 @@ static void show_link_netfilter(void) nf_link_count++; }

+ if (!nf_link_info) + return; + qsort(nf_link_info, nf_link_count, sizeof(*nf_link_info), netfilter_link_compar);

for (id = 0; id < nf_link_count; id++) {