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https://issues.apache.org/jira/browse/WW-5413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18098254#comment-18098254
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Lukasz Lenart commented on WW-5413:
-----------------------------------
[~rproserpio] PR ready, please review it if you have time :)
https://github.com/apache/struts/pull/1805
> Multipart misbehavior with commons-io 2.16.0 and 2.16.1
> -------------------------------------------------------
>
> Key: WW-5413
> URL: https://issues.apache.org/jira/browse/WW-5413
> Project: Struts 2
> Issue Type: Bug
> Components: Core
> Affects Versions: 6.3.0
> Reporter: Riccardo Proserpio
> Assignee: Lukasz Lenart
> Priority: Major
> Fix For: 7.3.0
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> commons-io 2.16.0 has broken the implementation of
> DeferredFileOutputStream changing the behavior of its superclass
> ThresholdingOutputStream: IO-854
>
> The class is used by commons-fileupload DiskFileItem, that is used by Struts
> to handle multipart uploads. The issue causes each multipart part to be read
> as empty.
>
> A fix has been implemented in 2.16.1. However, the fix exposes an issue in
> how the getFile of JakartaMultiPartRequest uses DiskFileItem, that causes it
> to mishandle zero length inputs.
>
> The issue is related to WW-5088 and WW-5146
>
> Moreover, the fix implemented for this issues seems to be dubious and affects
> not only file uploads but every field encoded as multipart/form-data: by
> forcing the diskfileitem threshold to be -1, each and every field was written
> to the filesystem.
>
> The behavior of threadshold -1 was underspecified and inconsistent with the
> commons-io implementation, and has been specified in 2.16.1.
>
> To really fix the issue, I suggest to avoid specifying -1 on the
> DiskFileItemFactory and to properly handle the case when the
> DiskFileItem.isInMemory() returns true in the JakartaMultiPartRequest.getFile
> method: in this case getStoreLocation() is defined to return null and the
> bytes should be read from memory instead.
>
> Avoiding always spilling to disk each and every multipart part should also be
> a performance win, considering that multipart can also be used to transfer
> normal form inputs and not only files.
>
> What do you think?
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