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The syzbot reported a memleak as follows:
BUG: memory leak
unreferenced object 0xffff888101b41d00 (size 120):
comm "kworker/u4:0", pid 8, jiffies 4294944270 (age 12.780s)
backtrace:
[<ffffffff8125dc56>] alloc_pid+0x66/0x560
[<ffffffff81226405>] copy_process+0x1465/0x25e0
[<ffffffff81227943>] kernel_clone+0xf3/0x670
[<ffffffff812281a1>] kernel_thread+0x61/0x80
[<ffffffff81253464>] call_usermodehelper_exec_work
[<ffffffff81253464>] call_usermodehelper_exec_work+0xc4/0x120
[<ffffffff812591c9>] process_one_work+0x2c9/0x600
[<ffffffff81259ab9>] worker_thread+0x59/0x5d0
[<ffffffff812611c8>] kthread+0x178/0x1b0
[<ffffffff8100227f>] ret_from_fork+0x1f/0x30
unreferenced object 0xffff888110ef5c00 (size 232):
comm "kworker/u4:0", pid 8414, jiffies 4294944270 (age 12.780s)
backtrace:
[<ffffffff8154a0cf>] kmem_cache_zalloc
[<ffffffff8154a0cf>] __alloc_file+0x1f/0xf0
[<ffffffff8154a809>] alloc_empty_file+0x69/0x120
[<ffffffff8154a8f3>] alloc_file+0x33/0x1b0
[<ffffffff8154ab22>] alloc_file_pseudo+0xb2/0x140
[<ffffffff81559218>] create_pipe_files+0x138/0x2e0
[<ffffffff8126c793>] umd_setup+0x33/0x220
[<ffffffff81253574>] call_usermodehelper_exec_async+0xb4/0x1b0
[<ffffffff8100227f>] ret_from_fork+0x1f/0x30
After the UMD process exits, the pipe_to_umh/pipe_from_umh and
tgid need to be released.
Fixes: d71fa5c9763c ("bpf: Add kernel module with user mode driver that populates bpffs.")
Reported-by: syzbot+44908bb56d2bfe56b28e@syzkaller.appspotmail.com
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210317030915.2865-1-qiang.zhang@windriver.com
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Add kernel module with user mode driver that populates bpffs with
BPF iterators.
$ mount bpffs /my/bpffs/ -t bpf
$ ls -la /my/bpffs/
total 4
drwxrwxrwt 2 root root 0 Jul 2 00:27 .
drwxr-xr-x 19 root root 4096 Jul 2 00:09 ..
-rw------- 1 root root 0 Jul 2 00:27 maps.debug
-rw------- 1 root root 0 Jul 2 00:27 progs.debug
The user mode driver will load BPF Type Formats, create BPF maps, populate BPF
maps, load two BPF programs, attach them to BPF iterators, and finally send two
bpf_link IDs back to the kernel.
The kernel will pin two bpf_links into newly mounted bpffs instance under
names "progs.debug" and "maps.debug". These two files become human readable.
$ cat /my/bpffs/progs.debug
id name attached
11 dump_bpf_map bpf_iter_bpf_map
12 dump_bpf_prog bpf_iter_bpf_prog
27 test_pkt_access
32 test_main test_pkt_access test_pkt_access
33 test_subprog1 test_pkt_access_subprog1 test_pkt_access
34 test_subprog2 test_pkt_access_subprog2 test_pkt_access
35 test_subprog3 test_pkt_access_subprog3 test_pkt_access
36 new_get_skb_len get_skb_len test_pkt_access
37 new_get_skb_ifindex get_skb_ifindex test_pkt_access
38 new_get_constant get_constant test_pkt_access
The BPF program dump_bpf_prog() in iterators.bpf.c is printing this data about
all BPF programs currently loaded in the system. This information is unstable
and will change from kernel to kernel as ".debug" suffix conveys.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200819042759.51280-4-alexei.starovoitov@gmail.com
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