From: Dongliang Mu <[email protected]>
When syzkaller injects fault into memory allocation at
bpf_prog_array_alloc, the kernel encounters a memory failure and
returns non-zero, thus leading to one WARN_ON at
bpf_cgroup_link_release. The stack trace is as follows:
__kmalloc+0x7e/0x3d0
bpf_prog_array_alloc+0x4f/0x60
compute_effective_progs+0x132/0x580
? __sanitizer_cov_trace_pc+0x1a/0x40
update_effective_progs+0x5e/0x260
__cgroup_bpf_detach+0x293/0x760
bpf_cgroup_link_release+0xad/0x400
bpf_link_free+0xca/0x190
bpf_link_put+0x161/0x1b0
bpf_link_release+0x33/0x40
__fput+0x286/0x9f0
Fix this by removing the WARN_ON for __cgroup_bpf_detach.
Reported-by: syzkaller <[email protected]>
Signed-off-by: Dongliang Mu <[email protected]>
---
kernel/bpf/cgroup.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 514b4681a90a..fdbdcee6c9fa 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -896,8 +896,8 @@ static void bpf_cgroup_link_release(struct bpf_link *link)
return;
}
- WARN_ON(__cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
- cg_link->type));
+ __cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
+ cg_link->type);
cg = cg_link->cgroup;
cg_link->cgroup = NULL;
--
2.25.1
On 2/27/22 2:40 PM, Dongliang Mu wrote:
> From: Dongliang Mu <[email protected]>
>
> When syzkaller injects fault into memory allocation at
> bpf_prog_array_alloc, the kernel encounters a memory failure and
> returns non-zero, thus leading to one WARN_ON at
> bpf_cgroup_link_release. The stack trace is as follows:
>
> __kmalloc+0x7e/0x3d0
> bpf_prog_array_alloc+0x4f/0x60
> compute_effective_progs+0x132/0x580
> ? __sanitizer_cov_trace_pc+0x1a/0x40
> update_effective_progs+0x5e/0x260
> __cgroup_bpf_detach+0x293/0x760
> bpf_cgroup_link_release+0xad/0x400
> bpf_link_free+0xca/0x190
> bpf_link_put+0x161/0x1b0
> bpf_link_release+0x33/0x40
> __fput+0x286/0x9f0
>
> Fix this by removing the WARN_ON for __cgroup_bpf_detach.
>
> Reported-by: syzkaller <[email protected]>
> Signed-off-by: Dongliang Mu <[email protected]>
> ---
> kernel/bpf/cgroup.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index 514b4681a90a..fdbdcee6c9fa 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -896,8 +896,8 @@ static void bpf_cgroup_link_release(struct bpf_link *link)
> return;
> }
>
> - WARN_ON(__cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
> - cg_link->type));
> + __cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
> + cg_link->type);
"Fixing" by removing WARN_ON is just papering over the issue which in this case as
mentioned is allocation failure on detach/teardown when allocating and recomputing
effective prog arrays..
> cg = cg_link->cgroup;
> cg_link->cgroup = NULL;
>
On Wed, Mar 2, 2022 at 12:28 AM Daniel Borkmann <[email protected]> wrote:
>
> On 2/27/22 2:40 PM, Dongliang Mu wrote:
> > From: Dongliang Mu <[email protected]>
> >
> > When syzkaller injects fault into memory allocation at
> > bpf_prog_array_alloc, the kernel encounters a memory failure and
> > returns non-zero, thus leading to one WARN_ON at
> > bpf_cgroup_link_release. The stack trace is as follows:
> >
> > __kmalloc+0x7e/0x3d0
> > bpf_prog_array_alloc+0x4f/0x60
> > compute_effective_progs+0x132/0x580
> > ? __sanitizer_cov_trace_pc+0x1a/0x40
> > update_effective_progs+0x5e/0x260
> > __cgroup_bpf_detach+0x293/0x760
> > bpf_cgroup_link_release+0xad/0x400
> > bpf_link_free+0xca/0x190
> > bpf_link_put+0x161/0x1b0
> > bpf_link_release+0x33/0x40
> > __fput+0x286/0x9f0
> >
> > Fix this by removing the WARN_ON for __cgroup_bpf_detach.
> >
> > Reported-by: syzkaller <[email protected]>
> > Signed-off-by: Dongliang Mu <[email protected]>
> > ---
> > kernel/bpf/cgroup.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> > index 514b4681a90a..fdbdcee6c9fa 100644
> > --- a/kernel/bpf/cgroup.c
> > +++ b/kernel/bpf/cgroup.c
> > @@ -896,8 +896,8 @@ static void bpf_cgroup_link_release(struct bpf_link *link)
> > return;
> > }
> >
> > - WARN_ON(__cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
> > - cg_link->type));
> > + __cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
> > + cg_link->type);
>
> "Fixing" by removing WARN_ON is just papering over the issue which in this case as
> mentioned is allocation failure on detach/teardown when allocating and recomputing
> effective prog arrays..
Hi Daniel,
you're right. This is not a good fix, any idea to fix the underlying
bug perfectly?
>
> > cg = cg_link->cgroup;
> > cg_link->cgroup = NULL;
> >
>