Re: [f2fs-dev] [PATCH] fs: f2fs: remove WARN_ON in f2fs_is_valid_blkaddr

[Chao Yu <chao@kernel.org>]

On 2022/4/9 14:42, Dongliang Mu wrote:
> On Sat, Apr 9, 2022 at 11:46 AM Chao Yu <chao@kernel.org> wrote:
>>
>> On 2022/4/9 9:34, Dongliang Mu wrote:
>>> On Sat, Apr 9, 2022 at 8:27 AM Chao Yu <chao@kernel.org> wrote:
>>>>
>>>> On 2022/4/8 13:22, Dongliang Mu wrote:
>>>>> From: Dongliang Mu <mudongliangabcd@gmail.com>
>>>>>
>>>>> In f2fs_is_valid_blkaddr, if type is DATA_GENERIC_ENHANCE or
>>>>> DATA_GENERIC_ENHANCE_READ, it invokes WARN_ON(1) not matter
>>>>> blkaddr is in the range or not.
>>>>
>>>> If we run into the path where we invoke WARN_ON(1) in f2fs_is_valid_blkaddr(),
>>>> It means f2fs image may be broken, or there is a bug in f2fs.
>>>>
>>>> So, do you suffer any related issue in your environment?
>>>
>>> related issue? Can you explain a little?
>>>
>>> If you mean if this warning occurs, any other issues or crash
>>
>> I mean have you seen any warning info printed in the path of
>> f2fs_is_valid_blkaddr() before applying this patch, and if so, w/ what
>> reproducer? or you just figure out this patch from perspective of code
>> review?
> 
> Yes, I have seen both warning information from Syzbot [1] and my local
> syzkaller instance.
> 
> In f2fs_is_valid_blkaddr, if the following condition is satisfied,
> i.e., blkaddr is not in the right range [2], it will directly invoke
> one WARN_ON.
> 
> if (unlikely(blkaddr >= MAX_BLKADDR(sbi) ||
>                   blkaddr < MAIN_BLKADDR(sbi))) {
> 
> This is the case on Syzbot.
> 
> Otherwise, it will jump into __is_bitmap_valid. And if the following
> condition is satisfied [3], it will trigger another WARN_ON.
> 
> exist = f2fs_test_bit(offset, se->cur_valid_map);
> if (!exist && type == DATA_GENERIC_ENHANCE) {
> 
> This appears in my local syzbot instance, but unfortunately it does
> not get any reproducer.

Oh, it occurs in syzbot test, I guess it is possible that f2fs prints such
warning info after blkaddr of node/data block was fuzzed to invalid one.

I prefer to keep WARN_ON() to catch more info of bugs found by non-fuzzed
type test.

Thoughts?

Thanks,

> 
> [1] https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsyzkaller.appspot.com%2Fbug%3Fextid%3D763ae12a2ede1d99d4dc&amp;data=04%7C01%7Cchao.yu%40oppo.com%7Cff92e63621b24fc75a4908da19f45860%7Cf1905eb1c35341c5951662b4a54b5ee6%7C0%7C0%7C637850834521060840%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=UVSSS9IknYLJHzqqJAN5HmPgJ8GNczvi6%2FuQf2n3vlY%3D&amp;reserved=0
> [2] https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Flatest%2Fsource%2Ffs%2Ff2fs%2Fcheckpoint.c%23L187&amp;data=04%7C01%7Cchao.yu%40oppo.com%7Cff92e63621b24fc75a4908da19f45860%7Cf1905eb1c35341c5951662b4a54b5ee6%7C0%7C0%7C637850834521060840%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=Sf%2Bx8WCAXf5c4%2Bins46saTsTN5uNTrnIceAP3oCWnQw%3D&amp;reserved=0
> [3] https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Flatest%2Fsource%2Ffs%2Ff2fs%2Fcheckpoint.c%23L135&amp;data=04%7C01%7Cchao.yu%40oppo.com%7Cff92e63621b24fc75a4908da19f45860%7Cf1905eb1c35341c5951662b4a54b5ee6%7C0%7C0%7C637850834521060840%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=Ly%2FBL5oFAWZmXwbN6TaYCExroDE8%2Fsli1alaJwR4wvU%3D&amp;reserved=0
> 
> 
>>
>> Thanks,
>>
>>> behaviors are generated? I tested on the syzbot. After removing the
>>> WARN_ON, there is no abnormal issue or crash behaviors followed with
>>> the corresponding reproducer.
>>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>> Fix this by removing WARN_ON.
>>>>>
>>>>> Note that, syzbot patch testing does not incur any further issues
>>>>>
>>>>> Reported-by: syzbot+763ae12a2ede1d99d4dc@syzkaller.appspotmail.com
>>>>> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
>>>>> ---
>>>>>     fs/f2fs/checkpoint.c | 2 --
>>>>>     1 file changed, 2 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>>> index f5366feea82d..521498b2dd8c 100644
>>>>> --- a/fs/f2fs/checkpoint.c
>>>>> +++ b/fs/f2fs/checkpoint.c
>>>>> @@ -158,7 +158,6 @@ static bool __is_bitmap_valid(struct f2fs_sb_info *sbi, block_t blkaddr,
>>>>>                 f2fs_err(sbi, "Inconsistent error blkaddr:%u, sit bitmap:%d",
>>>>>                          blkaddr, exist);
>>>>>                 set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>> -             WARN_ON(1);
>>>>>         }
>>>>>         return exist;
>>>>>     }
>>>>> @@ -196,7 +195,6 @@ bool f2fs_is_valid_blkaddr(struct f2fs_sb_info *sbi,
>>>>>                         f2fs_warn(sbi, "access invalid blkaddr:%u",
>>>>>                                   blkaddr);
>>>>>                         set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>> -                     WARN_ON(1);
>>>>>                         return false;
>>>>>                 } else {
>>>>>                         return __is_bitmap_valid(sbi, blkaddr, type);
> 
> 
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