Re: [PATCH 5/5] btrfs-progs: check/lowmem: fix path leakage when dev extents are invalid

[Nikolay Borisov <nborisov@suse.com>]

On 15.05.22 г. 13:55 ч., Qu Wenruo wrote:
> [BUG]
> When testing my new RAID56J code, there is a bug causing dev extents
> overlapping.
> 
> Although both modes can detect the problem, lowmem has leaked some
> extent buffers:
> 
>    $ btrfs check --mode=lowmem /dev/test/scratch1
>    Opening filesystem to check...
>    Checking filesystem on /dev/test/scratch1
>    UUID: 65775ce9-bb9d-4f61-a210-beea52eef090
>    [1/7] checking root items
>    [2/7] checking extents
>    ERROR: dev extent devid 1 offset 1095761920 len 1073741824 overlap with previous dev extent end 1096810496
>    ERROR: dev extent devid 2 offset 1351614464 len 1073741824 overlap with previous dev extent end 1352663040
>    ERROR: dev extent devid 3 offset 1351614464 len 1073741824 overlap with previous dev extent end 1352663040
>    ERROR: errors found in extent allocation tree or chunk allocation
>    [3/7] checking free space tree
>    [4/7] checking fs roots
>    [5/7] checking only csums items (without verifying data)
>    [6/7] checking root refs done with fs roots in lowmem mode, skipping
>    [7/7] checking quota groups skipped (not enabled on this FS)
>    found 3221372928 bytes used, error(s) found
>    total csum bytes: 0
>    total tree bytes: 147456
>    total fs tree bytes: 32768
>    total extent tree bytes: 16384
>    btree space waste bytes: 136231
>    file data blocks allocated: 3221225472
>     referenced 3221225472
>    extent buffer leak: start 30752768 len 16384
>    extent buffer leak: start 30752768 len 16384
>    extent buffer leak: start 30752768 len 16384
> 
> [CAUSE]
> In the function check_dev_item(), we iterate through all the dev
> extents, but when we found overlapping extents, we exit without
> releasing the path, causing extent buffer leakage.
> 
> [FIX]
> Just release the path before we exit the function.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>


This can go completely independently from the raid56j code.