[PATCH 4/4] fs: free unused dentries

[Ahmad Fatoum]

Hello Sascha,

On 9/15/20 9:12 AM, Sascha Hauer wrote:
> On Tue, Sep 15, 2020 at 07:25:15AM +0200, Ahmad Fatoum wrote:
>> Hello Sascha,
>>
>> On 9/14/20 3:06 PM, Sascha Hauer wrote:
>>> So far we only ever freed dentries when the filesystem they are on is
>>> unmounted. With this patch we actually trust reference counting and free
>>> the dentries once the reference count hits zero.
>>
>> Unless I revert this patch, I run into a crash doing:
>>
>> dd if=/dev/zero of=barebox.env count=1
>> ./barebox --image=barebox.env
>> barebox at barebox sandbox:/ saveenv
>> saving environment
> 
> "saveenv" answers with: "saveenv: No such file or directory". Did you
> mean to do a "saveenv /dev/fd0"?
> 
>> barebox at barebox sandbox:/ reset
>> =================================================================
>> ==894761==ERROR: AddressSanitizer: heap-use-after-free on address 0x60e000005d70 at pc 0x5617cfde210a bp 0x7ffff89957d0 sp 0x7ffff89957c8
> 
> I can't reproduce this here unfortunately.

Sorry, should've been ./barebox --env=barebox.env

I can reproduce it with upstream/next (91a23b64445b8861acbfd96fcc03082b343b0211)
and sandbox_defconfig (+CONFIG_RESET). saveenv; reset results in a segmentation fault.
CONFIG_KASAN=y
CONFIG_MALLOC_LIBC=y
gives the better debugging output.

Cheers,
Ahmad

> 
> Sascha
> 
> 

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