This is a note to let you know that I've just added the patch titled
bpftool: Fix undefined behavior in qsort(NULL, 0, ...)
to the 6.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpftool-fix-undefined-behavior-in-qsort-null-0.patch
and it can be found in the queue-6.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 25be26f6efc7841955167b8ee51bc4779ff29f44
Author: Kuan-Wei Chiu <visitorckw@xxxxxxxxx>
Date: Tue Sep 10 23:02:07 2024 +0800
bpftool: Fix undefined behavior in qsort(NULL, 0, ...)
[ 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@xxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Reviewed-by: Quentin Monnet <qmo@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20240910150207.3179306-1-visitorckw@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
index ad2ea6cf2db11..0f2106218e1f0 100644
--- a/tools/bpf/bpftool/net.c
+++ b/tools/bpf/bpftool/net.c
@@ -824,6 +824,9 @@ 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++) {
