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Message-ID: <CAEf4Bza03=MLPJN1fY+93W4=orqt=nHzQuUBw=7cz-qAwFQdvA@mail.gmail.com> Date: Thu, 27 Oct 2022 13:34:47 -0700 From: Andrii Nakryiko <andrii.nakryiko@...il.com> To: Wang Yufen <wangyufen@...wei.com> Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com, andrii@...nel.org, martin.lau@...ux.dev, yhs@...com, joe@...d.net.nz Subject: Re: [PATCH net] bpf: Fix memory leaks in __check_func_call On Thu, Oct 27, 2022 at 3:03 AM Wang Yufen <wangyufen@...wei.com> wrote: > > kmemleak reports this issue: > > unreferenced object 0xffff88817139d000 (size 2048): > comm "test_progs", pid 33246, jiffies 4307381979 (age 45851.820s) > hex dump (first 32 bytes): > 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > [<0000000045f075f0>] kmalloc_trace+0x27/0xa0 > [<0000000098b7c90a>] __check_func_call+0x316/0x1230 > [<00000000b4c3c403>] check_helper_call+0x172e/0x4700 > [<00000000aa3875b7>] do_check+0x21d8/0x45e0 > [<000000001147357b>] do_check_common+0x767/0xaf0 > [<00000000b5a595b4>] bpf_check+0x43e3/0x5bc0 > [<0000000011e391b1>] bpf_prog_load+0xf26/0x1940 > [<0000000007f765c0>] __sys_bpf+0xd2c/0x3650 > [<00000000839815d6>] __x64_sys_bpf+0x75/0xc0 > [<00000000946ee250>] do_syscall_64+0x3b/0x90 > [<0000000000506b7f>] entry_SYSCALL_64_after_hwframe+0x63/0xcd > > The root case here is: In function prepare_func_exit(), the callee is > not released in the abnormal scenario after "state->curframe--;". > > In addition, function __check_func_call() has a similar problem. In > the abnormal scenario before "state->curframe++;", the callee is alse > not released. For prepare_func_exit, wouldn't it be correct and cleaner to just move state->curframe--; to the very bottom of the function, right when we free callee and reset frame[] pointer to NULL? For __check_func_call, please use err_out label name to disambiguate it from the "err" variable. > > Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") > Fixes: fd978bf7fd31 ("bpf: Add reference tracking to verifier") > Signed-off-by: Wang Yufen <wangyufen@...wei.com> > --- > kernel/bpf/verifier.c | 25 ++++++++++++++++--------- > 1 file changed, 16 insertions(+), 9 deletions(-) > [...]
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