This is a note to let you know that I've just added the patch titled
bpf: Fix mount source show for bpffs
to the 5.15-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:
bpf-fix-mount-source-show-for-bpffs.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1e9d74660d4df625b0889e77018f9e94727ceacd Mon Sep 17 00:00:00 2001
From: Yafang Shao <laoar.shao@xxxxxxxxx>
Date: Sat, 8 Jan 2022 13:46:23 +0000
Subject: bpf: Fix mount source show for bpffs
From: Yafang Shao <laoar.shao@xxxxxxxxx>
commit 1e9d74660d4df625b0889e77018f9e94727ceacd upstream.
We noticed our tc ebpf tools can't start after we upgrade our in-house kernel
version from 4.19 to 5.10. That is because of the behaviour change in bpffs
caused by commit d2935de7e4fd ("vfs: Convert bpf to use the new mount API").
In our tc ebpf tools, we do strict environment check. If the environment is
not matched, we won't allow to start the ebpf progs. One of the check is whether
bpffs is properly mounted. The mount information of bpffs in kernel-4.19 and
kernel-5.10 are as follows:
- kernel 4.19
$ mount -t bpf bpffs /sys/fs/bpf
$ mount -t bpf
bpffs on /sys/fs/bpf type bpf (rw,relatime)
- kernel 5.10
$ mount -t bpf bpffs /sys/fs/bpf
$ mount -t bpf
none on /sys/fs/bpf type bpf (rw,relatime)
The device name in kernel-5.10 is displayed as none instead of bpffs, then our
environment check fails. Currently we modify the tools to adopt to the kernel
behaviour change, but I think we'd better change the kernel code to keep the
behavior consistent.
After this change, the mount information will be displayed the same with the
behavior in kernel-4.19, for example:
$ mount -t bpf bpffs /sys/fs/bpf
$ mount -t bpf
bpffs on /sys/fs/bpf type bpf (rw,relatime)
Fixes: d2935de7e4fd ("vfs: Convert bpf to use the new mount API")
Suggested-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20220108134623.32467-1-laoar.shao@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/bpf/inode.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -648,12 +648,22 @@ static int bpf_parse_param(struct fs_con
int opt;
opt = fs_parse(fc, bpf_fs_parameters, param, &result);
- if (opt < 0)
+ if (opt < 0) {
/* We might like to report bad mount options here, but
* traditionally we've ignored all mount options, so we'd
* better continue to ignore non-existing options for bpf.
*/
- return opt == -ENOPARAM ? 0 : opt;
+ if (opt == -ENOPARAM) {
+ opt = vfs_parse_fs_param_source(fc, param);
+ if (opt != -ENOPARAM)
+ return opt;
+
+ return 0;
+ }
+
+ if (opt < 0)
+ return opt;
+ }
switch (opt) {
case OPT_MODE:
Patches currently in stable-queue which might be from laoar.shao@xxxxxxxxx are
queue-5.15/bpf-fix-mount-source-show-for-bpffs.patch
