Re: [PATCH bpf 3/7] bpf: Free dynamically allocated bits in bpf_iter_bits_destroy()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi,

On 10/9/2024 2:26 AM, Andrii Nakryiko wrote:
> On Tue, Oct 8, 2024 at 2:05 AM Hou Tao <houtao@xxxxxxxxxxxxxxx> wrote:
>> From: Hou Tao <houtao1@xxxxxxxxxx>
>>
>> bpf_iter_bits_destroy() uses "kit->nr_bits <= 64" to check whether the
>> bits are dynamically allocated. However, the check is incorrect and may
>> cause a kmemleak as shown below:
>>
>> unreferenced object 0xffff88812628c8c0 (size 32):
>>   comm "swapper/0", pid 1, jiffies 4294727320
>>   hex dump (first 32 bytes):
>>     b0 c1 55 f5 81 88 ff ff f0 f0 f0 f0 f0 f0 f0 f0  ..U.............
>>     f0 f0 f0 f0 f0 f0 f0 f0 00 00 00 00 00 00 00 00  ................
>>   backtrace (crc 781e32cc):
>>     [<00000000c452b4ab>] kmemleak_alloc+0x4b/0x80
>>     [<0000000004e09f80>] __kmalloc_node_noprof+0x480/0x5c0
>>     [<00000000597124d6>] __alloc.isra.0+0x89/0xb0
>>     [<000000004ebfffcd>] alloc_bulk+0x2af/0x720
>>     [<00000000d9c10145>] prefill_mem_cache+0x7f/0xb0
>>     [<00000000ff9738ff>] bpf_mem_alloc_init+0x3e2/0x610
>>     [<000000008b616eac>] bpf_global_ma_init+0x19/0x30
>>     [<00000000fc473efc>] do_one_initcall+0xd3/0x3c0
>>     [<00000000ec81498c>] kernel_init_freeable+0x66a/0x940
>>     [<00000000b119f72f>] kernel_init+0x20/0x160
>>     [<00000000f11ac9a7>] ret_from_fork+0x3c/0x70
>>     [<0000000004671da4>] ret_from_fork_asm+0x1a/0x30
>>
>> That is because nr_bits will be set as zero in bpf_iter_bits_next()
>> after all bits have been iterated.
>>
> so maybe don't touch nr_bits and just use `kit->bit >= kit->nr_bits`
> condition to know when iterator is done?

Good idea. That would be simpler. Will do in v2.
>
>> Fix the problem by introducing an extra allocated status in
>> bpf_iter_bits and using it to indicate whether the bits are
>> dynamically allocated.





[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux