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bpf: fix bpf_prog_array_copy_to_user warning from perf event prog query

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syzkaller tried to perform a prog query in perf_event_query_prog_array()
where struct perf_event_query_bpf had an ids_len of 1,073,741,353 and
thus causing a warning due to failed kcalloc() allocation out of the
bpf_prog_array_copy_to_user() helper. Given we cannot attach more than
64 programs to a perf event, there's no point in allowing huge ids_len.
Therefore, allow a buffer that would fix the maximum number of ids and
also add a __GFP_NOWARN to the temporary ids buffer.

Fixes: f371b304f1 ("bpf/tracing: allow user space to query prog array on the same tp")
Fixes: 0911287ce3 ("bpf: fix bpf_prog_array_copy_to_user() issues")
Reported-by: syzbot+cab5816b0edbabf598b3@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2018-02-14 15:31:00 +01:00 committed by Alexei Starovoitov
parent 7fc17e909e
commit 9c481b908b
2 changed files with 3 additions and 1 deletions
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2
kernel/bpf/core.c
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@ -1590,7 +1590,7 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
* so always copy 'cnt' prog_ids to the user. * so always copy 'cnt' prog_ids to the user.
* In a rare race the user will see zero prog_ids * In a rare race the user will see zero prog_ids
*/ */
ids = kcalloc(cnt, sizeof(u32), GFP_USER); ids = kcalloc(cnt, sizeof(u32), GFP_USER | __GFP_NOWARN);
if (!ids) if (!ids)
return -ENOMEM; return -ENOMEM;
rcu_read_lock(); rcu_read_lock();

2
kernel/trace/bpf_trace.c
View File

@ -872,6 +872,8 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
return -EINVAL; return -EINVAL;
if (copy_from_user(&query, uquery, sizeof(query))) if (copy_from_user(&query, uquery, sizeof(query)))
return -EFAULT; return -EFAULT;
if (query.ids_len > BPF_TRACE_MAX_PROGS)
return -E2BIG;
mutex_lock(&bpf_event_mutex); mutex_lock(&bpf_event_mutex);
ret = bpf_prog_array_copy_info(event->tp_event->prog_array, ret = bpf_prog_array_copy_info(event->tp_event->prog_array,