Messages in this thread | | | Subject | Re: [RESEND][PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline | From | Daniel Borkmann <> | Date | Mon, 11 Oct 2021 15:44:09 +0200 |
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[ +Roman ]
On 10/8/21 2:46 AM, quanyang.wang@windriver.com wrote: > From: Quanyang Wang <quanyang.wang@windriver.com> > > When enabling CONFIG_CGROUP_BPF, kmemleak can be observed by running > the command as below: > > $mount -t cgroup -o none,name=foo cgroup cgroup/ > $umount cgroup/ > > unreferenced object 0xc3585c40 (size 64): > comm "mount", pid 425, jiffies 4294959825 (age 31.990s) > hex dump (first 32 bytes): > 01 00 00 80 84 8c 28 c0 00 00 00 00 00 00 00 00 ......(......... > 00 00 00 00 00 00 00 00 6c 43 a0 c3 00 00 00 00 ........lC...... > backtrace: > [<e95a2f9e>] cgroup_bpf_inherit+0x44/0x24c > [<1f03679c>] cgroup_setup_root+0x174/0x37c > [<ed4b0ac5>] cgroup1_get_tree+0x2c0/0x4a0 > [<f85b12fd>] vfs_get_tree+0x24/0x108 > [<f55aec5c>] path_mount+0x384/0x988 > [<e2d5e9cd>] do_mount+0x64/0x9c > [<208c9cfe>] sys_mount+0xfc/0x1f4 > [<06dd06e0>] ret_fast_syscall+0x0/0x48 > [<a8308cb3>] 0xbeb4daa8 > > This is because that root_cgrp->bpf.refcnt.data is allocated by the > function percpu_ref_init in cgroup_bpf_inherit which is called by > cgroup_setup_root when mounting, but not freed along with root_cgrp > when umounting. Adding cgroup_bpf_offline which calls percpu_ref_kill > to cgroup_kill_sb can free root_cgrp->bpf.refcnt.data in umount path. > > Fixes: 2b0d3d3e4fcfb ("percpu_ref: reduce memory footprint of percpu_ref in fast path") > Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com> > --- > One of the recipients' email is wrong, so I resend this patch. > Sorry for any confusion caused. > --- > kernel/cgroup/cgroup.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index 570b0c97392a9..183736ad72f2b 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -2187,8 +2187,10 @@ static void cgroup_kill_sb(struct super_block *sb) > * And don't kill the default root. > */ > if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root && > - !percpu_ref_is_dying(&root->cgrp.self.refcnt)) > + !percpu_ref_is_dying(&root->cgrp.self.refcnt)) { > + cgroup_bpf_offline(&root->cgrp); > percpu_ref_kill(&root->cgrp.self.refcnt); > + } > cgroup_put(&root->cgrp);
Doesn't cgroup_bpf_offline() internally bump the root cgroup's refcount via cgroup_get()? How does this relate to the single cgroup_put() in the above line? Would have been nice to see the commit msg elaborate more on this.
> kernfs_kill_sb(sb); > } >
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