Bug #3197: Found an UAF bug in /src/chunk.c - Lighttpd - lighty labs

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Bug #3197

closed

Found an UAF bug in /src/chunk.c

Added by shangzhi_xu about 1 year ago. Updated about 1 year ago.

Status:

Fixed

Priority:

Normal

Category:

core

Target version:

1.4.70

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Description

File: /src/chunk.c
Function: chunkqueue_chunk_file_viewadj

Description:

munmap(cfv->mptr, (size_t)cfv->mlen);

is called in this function [Line 1715]
Then in line 1719

c->file.view = chunk_file_view_failed(cfv);

is called, in this function, it called chunk_file_view_release(cfv)
but in function chunk_file_view_release ，

munmap(cfv->mptr, (size_t)cfv->mlen);

is called again as cfv->mptr != MAP_FAILED;

Suggestion:
I found that /*cfv->mptr= MAP_FAILED;*//*(assigned below)*/ was commented out at [Line 1716], which lead to this bug, maybe we should delete the comment mark on this statement.

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Updated by gstrauss about 1 year ago

Category set to core
Status changed from New to Patch Pending
Target version changed from 1.4.xx to 1.4.70

Configuring lighttpd to use mmap is not the default in the build and must be enabled in the build with ./configure --enable-mmap

If you found this with a static analyzer, please provide details.

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Updated by shangzhi_xu about 1 year ago

gstrauss wrote in #note-1:

Configuring lighttpd to use mmap is not the default in the build and must be enabled in the build with ./configure --enable-mmap

If you found this with a static analyzer, please provide details.

Thanks for your reply! Yes, I found it with static analysis with Goshawk https://github.com/Yunlongs/Goshawk. The details are just like I mentioned above. I think the trace in chunk.c [Line 1715]->[ line 1719]->[Line 156] might lead to a bug. So if you need any further information or details, please tell me~ I'll provide them as soon as possible.

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Updated by gstrauss about 1 year ago

The chunk is generally opened prior to this function being called, and this feature is intended to be enabled in the lighttpd build on systems where the filesystem is trusted. Still, to fix this potential issue, I'll move the call to chunk_open_file_chunk() to the top of the func. Thank you for reporting the issue.

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