Bug 60267 - Inconsistent symlink traversal results
Summary: Inconsistent symlink traversal results
Alias: None
Product: Runtime
Classification: Mono
Component: io-layer ()
Version: master
Hardware: PC Linux
: Normal normal
Target Milestone: Future Cycle (TBD)
Assignee: Alexis Christoforides
Depends on:
Reported: 2017-10-19 09:30 UTC by Piotr Zierhoffer
Modified: 2018-01-05 13:27 UTC (History)
6 users (show)

Tags: bugpool-archive
Is this bug a regression?: ---
Last known good build:

The test program (523 bytes, text/x-csharp)
2017-10-19 09:30 UTC, Piotr Zierhoffer

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Description Piotr Zierhoffer 2017-10-19 09:30:24 UTC
Created attachment 25370 [details]
The test program

The bug appears when you try to verify the existence of a file in a directory, that is a symlink. The symlink may not point to a directory higher in the directory structure, it has to be on another branch. Moreover, you have to use ".." in a path, just after pointing to the directory in question

Steps to reproduce:

1) in the exe directory create the following directory structure:

-> test/
---> test_file
-> test3 -> test/test2 (test3 is a symlink to test/test2 dir. This structure is crucial)

2) run the attached code.

It checks the existence of "test3/../test3/" directory.

Directory.Exists fails, but Directory.GetFileSystemEntries works (prints the "test_file").

The same code DOES work on another directory structure:

-> test/
--> test_file
-> test2 -> test (test2 is a symlink to test dir)

Expected results:

Directory.Exists should understand symlinks, and handling of different directory structures should be consistent.
Comment 1 Ludovic Henry 2017-11-10 16:08:45 UTC
I can reproduce with Mono (2017-10/ce494e3d152)

To reproduce, run following commands:
> mkdir test
> mkdir test/test2
> touch test/test2/test_file
> ln -s test/test2 test3
> csc repro.cs && mono repro.exe

Expected output:
> False
> True
> test3/../test3/test_file

Actual output:
> False
> False
> test3/../test3/test_file
Comment 2 Alexis Christoforides 2017-11-14 23:47:05 UTC
It seems that the lstat() syscall itself does not like that path. The solution may have to be part of mono_portability_find_file_internal()

Directory.Exists does work as expected under .NET Core 2.0.
Comment 3 Alexis Christoforides 2017-11-17 00:37:21 UTC
Candidate fix at https://github.com/mono/mono/pull/6039
Comment 4 Alexis Christoforides 2017-11-21 03:33:22 UTC
Fix merged to master