Fix up buffer management getting network roots #21068

jborean93 · 2024-01-14T00:27:06Z

PR Summary

Fixes the logic used when getting the PSDrive DisplayRoot for network PSDrive paths to exclude null terminators.

There are no tests added because the original issue was that we ran with DEBUG mode that didn't go across the problematic code. In this case we are now testing the problematic scenario which is the more common of the two.

PR Context

Fixes: #21064

PR Checklist

iSazonov

@jborean93 Thanks for investigating the issue!

Since you removed #if Debug it would be great to add test for fallback code branch (name length > MAXPATH).

iSazonov · 2024-01-14T08:47:56Z

src/System.Management.Automation/engine/Interop/Windows/WNetGetConnection.cs

                    {
-                        // exclude null terminator
-                        uncPath = uncBuffer.Slice(0, (int)bufferSize - 1).ToString();
+                        uncBuffer = rentedArray = ArrayPool<char>.Shared.Rent((int)bufferSize);


There's a problem here if there are multiple iterations (> 2). We must return the previous array.
In my opinion, this loop is unnecessary. But if you still want to keep it, the pattern should be similar to:

char[]? toReturn = rentedArray; uncBuffer = rentedArray = ArrayPool<char>.Shared.Rent((int)bufferSize); if (toReturn is not null) { ArrayPool<char>.Shared.Return(toReturn); }

I've updated the code to return the rented array in all cases, I've kept the loop for now but if others object I can change it again.

I've kept the loop because now it only calls the function once and shared the same logic for handling errors and how to read the output on success.

src/System.Management.Automation/engine/Interop/Windows/WNetGetConnection.cs

Fixes the logic used when getting the PSDrive DisplayRoot for network PSDrive paths to exclude null terminators.

pull-request-quantifier-deprecated · 2024-01-14T23:01:17Z

This PR has 32 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

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Label      : Extra Small
Size       : +15 -17
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Total files changed: 1

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.cs : +15 -17

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jborean93 · 2024-01-14T23:06:06Z

Since you removed #if Debug it would be great to add test for fallback code branch (name length > MAXPATH).

I would love to but seems like the underlying Win32 API WNetAddConnection3 is unable to handle paths that exceed MAX_PATH. If someone knows how to do this I'm happy to add a test but for now the current test will check the most common scenario unlike before.

iSazonov · 2024-01-15T05:32:41Z

Since you removed #if Debug it would be great to add test for fallback code branch (name length > MAXPATH).

I would love to but seems like the underlying Win32 API WNetAddConnection3 is unable to handle paths that exceed MAX_PATH. If someone knows how to do this I'm happy to add a test but for now the current test will check the most common scenario unlike before.

If Windows 10+ support long pathы the function could do the same. I do not know, but it is possible. Or it could even be added in the future.
As for test, we can use test hooks. See

PowerShell/src/System.Management.Automation/engine/Utils.cs

Line 1551 in e453c00

public static class InternalTestHooks

jborean93 · 2024-01-15T05:53:42Z

If Windows 10+ support long pathы the function could do the same. I do not know, but it is possible. Or it could even be added in the future.

I tested by calling the WNet API directly with both a normal and NT path prefix \\?\UNC\.... Ultimately I think the effort in setting all this up just adds further complexity for a scenario that might not even be possible.

iSazonov · 2024-01-15T09:15:02Z

If Windows 10+ support long pathы the function could do the same. I do not know, but it is possible. Or it could even be added in the future.

I tested by calling the WNet API directly with both a normal and NT path prefix \\?\UNC\.... Ultimately I think the effort in setting all this up just adds further complexity for a scenario that might not even be possible.

We should either remove the loop if this event is improbable or add a test.

jborean93 · 2024-01-15T09:44:55Z

Someone is free to continue on with this PR if they wish to do so. I’ve got no desire to continue to work on something that most likely will continue to sit for weeks before it is even looked at by the pwsh team.

adityapatwardhan · 2024-03-12T20:13:33Z

Removed backport label as this is not merged

pull-request-quantifier-deprecated bot added the Extra Small label Jan 14, 2024

jborean93 mentioned this pull request Jan 14, 2024

Get-PSDrive returns incorrect DisplayRoot property for mounted drive letters in 7.4.1 #21064

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iSazonov reviewed Jan 14, 2024

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Fix up buffer management getting network roots

aca9d8c

Fixes the logic used when getting the PSDrive DisplayRoot for network PSDrive paths to exclude null terminators.

SteveL-MSFT added BackPort-7.4.x-Consider CommunityDay-Small A small PR that the PS team has identified to prioritize to review labels Jan 14, 2024

Use builtin pointer to string method and ensure rented array is returned

dcbcb77

jborean93 closed this Jan 15, 2024

adityapatwardhan removed the BackPort-7.4.x-Consider label Mar 12, 2024

jborean93 mentioned this pull request Nov 17, 2024

Fix up buffer management getting network roots #24600

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jborean93 commented Jan 14, 2024

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