Fix absolute path check when loading hostfxr/hostpolicy/coreclr #116597

elinor-fung · 2025-06-12T19:13:21Z

On Windows, we were incorrectly only checking for <letter>: and incorrectly determining that UNC and device paths were not absolute. This updates pal::is_path_rooted to match the managed Path.IsPathRooted and adds a pal::is_path_absolute with the logic of Path.IsPartiallyQualified

See #116521
cc @dotnet/appmodel @AaronRobinsonMSFT @jkotas

We should backport as well.

dotnet-policy-service · 2025-06-12T19:13:55Z

Tagging subscribers to this area: @vitek-karas, @agocke, @VSadov
See info in area-owners.md if you want to be subscribed.

Copilot

Pull Request Overview

This PR corrects the determination of absolute paths on Windows by introducing a new pal::is_path_absolute that aligns with .NET’s logic and updating existing checks to use it. It also enhances the rooted-path test on Windows, adds Unix support for is_path_absolute, and includes tests for device path scenarios.

Implement is_path_absolute and expand is_path_rooted on Windows
Switch all corehost/fxr/hostpolicy resolvers to use is_path_absolute
Add Windows device-path tests in installer activation suites

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/native/corehost/hostpolicy/standalone/coreclr_resolver.cpp	Use `is_path_absolute` instead of `is_path_rooted`
src/native/corehost/hostmisc/pal.windows.cpp	Add `is_path_absolute`, refine `is_path_rooted`
src/native/corehost/hostmisc/pal.unix.cpp	Add `is_path_absolute` delegating to `is_path_rooted`
src/native/corehost/hostmisc/pal.h	Declare new `is_path_absolute` API
src/native/corehost/fxr_resolver.h	Update hostfxr load check to use `is_path_absolute`
src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp	Switch hostpolicy path check to `is_path_absolute`
src/native/corehost/corehost.cpp	Add detailed error log when fxr resolution fails
src/native/corehost/apphost/standalone/hostfxr_resolver.cpp	Use `is_path_absolute` for apphost fxr path validation
src/installer/tests/HostActivation.Tests/SelfContainedAppLaunch.cs	Add Windows device-path launch tests
src/installer/tests/HostActivation.Tests/FrameworkDependentAppLaunch.cs	Add Windows device-path DotNetRoot tests

Comments suppressed due to low confidence (2)

src/native/corehost/hostmisc/pal.h:345

Consider adding a doc comment above is_path_absolute describing its behavior (UNC, device paths, drive-letter paths) to aid future maintainers.

bool is_path_absolute(const string_t& path);

src/installer/tests/HostActivation.Tests/SelfContainedAppLaunch.cs:162

Add a test case for a standard UNC network share path (e.g., \\server\\share\\app.exe) to ensure UNC paths are recognized as absolute.

public void DevicePath()

jkotas · 2025-06-12T20:09:05Z

src/native/corehost/hostmisc/pal.h

@@ -342,6 +342,7 @@ namespace pal

    bool get_default_breadcrumb_store(string_t* recv);
    bool is_path_rooted(const string_t& path);


Are all remaining uses of is_path_rooted correct?

is_path_rooted is kind of broken concept. It rarely does what you expect.

Switch ones where the intent is checking for absolute path to is_path_fully_qualified. Remaining are around appending paths, where I think we do want is_path_rooted (matches Path.Combine logic).

Path.Combine has similar set of issues - it was one of the reasons for introducing Path.Join.

Are there situations in append_path where we can end up with path2 that is rooted but not fully qualified?

If there are situations like that, the behavior will depend on current directory again that's generally a security problem. If there are no situations like that, it does not matter whether we use is_path_fully_qualified or is_path_rooted.

Ideally, I think we would switch to Path.Join like API - but that is nice to have clean up that's not appropriate for servicing.

The only case is if the user explicitly did some configuration to specify a path that is rooted but not fully qualified - for the environment variable for bundle extraction directory or a custom sdk path in global.json, we'd use that rooted, not fully qualified path.

I'll look at making append_path more Path.Join-like in the future.

src/native/corehost/hostmisc/pal.windows.cpp

elinor-fung · 2025-06-16T17:09:24Z

/backport to release/9.0-staging

github-actions · 2025-06-16T17:09:33Z

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/15687286225

elinor-fung · 2025-06-16T17:09:44Z

/backport to release/8.0-staging

github-actions · 2025-06-16T17:09:53Z

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/15687292495

github-actions · 2025-06-16T17:11:16Z

@elinor-fung backporting to "release/9.0-staging" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Fix absolute path check when loading hostfxr/hostpolicy/coreclr
Using index info to reconstruct a base tree...
M	src/native/corehost/apphost/standalone/hostfxr_resolver.cpp
M	src/native/corehost/corehost.cpp
M	src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp
M	src/native/corehost/fxr_resolver.h
M	src/native/corehost/hostmisc/pal.h
M	src/native/corehost/hostmisc/pal.unix.cpp
M	src/native/corehost/hostmisc/pal.windows.cpp
M	src/native/corehost/hostpolicy/standalone/coreclr_resolver.cpp
Falling back to patching base and 3-way merge...
Auto-merging src/native/corehost/hostpolicy/standalone/coreclr_resolver.cpp
CONFLICT (content): Merge conflict in src/native/corehost/hostpolicy/standalone/coreclr_resolver.cpp
Auto-merging src/native/corehost/hostmisc/pal.windows.cpp
Auto-merging src/native/corehost/hostmisc/pal.unix.cpp
Auto-merging src/native/corehost/hostmisc/pal.h
Auto-merging src/native/corehost/fxr_resolver.h
CONFLICT (content): Merge conflict in src/native/corehost/fxr_resolver.h
Auto-merging src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp
CONFLICT (content): Merge conflict in src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp
Auto-merging src/native/corehost/corehost.cpp
Auto-merging src/native/corehost/apphost/standalone/hostfxr_resolver.cpp
CONFLICT (content): Merge conflict in src/native/corehost/apphost/standalone/hostfxr_resolver.cpp
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 Fix absolute path check when loading hostfxr/hostpolicy/coreclr
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

github-actions · 2025-06-16T17:11:40Z

@elinor-fung backporting to "release/8.0-staging" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Fix absolute path check when loading hostfxr/hostpolicy/coreclr
Using index info to reconstruct a base tree...
M	src/native/corehost/apphost/standalone/hostfxr_resolver.cpp
M	src/native/corehost/corehost.cpp
M	src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp
M	src/native/corehost/fxr_resolver.h
M	src/native/corehost/hostmisc/pal.h
M	src/native/corehost/hostmisc/pal.unix.cpp
M	src/native/corehost/hostmisc/pal.windows.cpp
M	src/native/corehost/hostpolicy/standalone/coreclr_resolver.cpp
Falling back to patching base and 3-way merge...
Auto-merging src/native/corehost/hostpolicy/standalone/coreclr_resolver.cpp
CONFLICT (content): Merge conflict in src/native/corehost/hostpolicy/standalone/coreclr_resolver.cpp
Auto-merging src/native/corehost/hostmisc/pal.windows.cpp
Auto-merging src/native/corehost/hostmisc/pal.unix.cpp
Auto-merging src/native/corehost/hostmisc/pal.h
Auto-merging src/native/corehost/fxr_resolver.h
CONFLICT (content): Merge conflict in src/native/corehost/fxr_resolver.h
Auto-merging src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp
CONFLICT (content): Merge conflict in src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp
Auto-merging src/native/corehost/corehost.cpp
Auto-merging src/native/corehost/apphost/standalone/hostfxr_resolver.cpp
CONFLICT (content): Merge conflict in src/native/corehost/apphost/standalone/hostfxr_resolver.cpp
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 Fix absolute path check when loading hostfxr/hostpolicy/coreclr
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

elinor-fung · 2025-06-17T21:05:33Z

/backport to release/9.0-staging

github-actions · 2025-06-17T21:05:42Z

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/15718023739

github-actions · 2025-06-17T21:07:26Z

@elinor-fung backporting to "release/9.0-staging" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Fix absolute path check when loading hostfxr/hostpolicy/coreclr
Applying: Add tests
Applying: PR feedback
error: sha1 information is lacking or useless (src/native/corehost/apphost/standalone/hostfxr_resolver.cpp).
error: could not build fake ancestor
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0003 PR feedback
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

elinor-fung · 2025-06-18T00:13:22Z

/backport to release/8.0-staging

github-actions · 2025-06-18T00:13:33Z

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/15720742824

github-actions · 2025-06-18T00:15:22Z

@elinor-fung backporting to "release/8.0-staging" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Fix absolute path check when loading hostfxr/hostpolicy/coreclr
Applying: Add tests
Using index info to reconstruct a base tree...
A	src/installer/tests/HostActivation.Tests/FrameworkDependentAppLaunch.cs
A	src/installer/tests/HostActivation.Tests/SelfContainedAppLaunch.cs
Falling back to patching base and 3-way merge...
CONFLICT (modify/delete): src/installer/tests/HostActivation.Tests/SelfContainedAppLaunch.cs deleted in HEAD and modified in Add tests. Version Add tests of src/installer/tests/HostActivation.Tests/SelfContainedAppLaunch.cs left in tree.
Auto-merging src/installer/tests/HostActivation.Tests/PortableAppActivation.cs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0002 Add tests
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

elinor-fung added 2 commits June 12, 2025 12:00

Fix absolute path check when loading hostfxr/hostpolicy/coreclr

6b4e030

Add tests

32b5102

elinor-fung requested review from agocke, AaronRobinsonMSFT and Copilot June 12, 2025 19:13

elinor-fung added the area-Host label Jun 12, 2025

dotnet-policy-service bot assigned elinor-fung Jun 12, 2025

Copilot AI reviewed Jun 12, 2025

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jkotas reviewed Jun 12, 2025

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AaronRobinsonMSFT reviewed Jun 12, 2025

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elinor-fung added 2 commits June 12, 2025 14:53

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build-analysis bot mentioned this pull request Jun 13, 2025

iOS.Device.LibraryMode.Test: failed to determine exit code - RETURN_CODE_NOT_SET #116558

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AaronRobinsonMSFT approved these changes Jun 13, 2025

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elinor-fung merged commit 22ccb05 into dotnet:main Jun 16, 2025
148 of 150 checks passed

elinor-fung deleted the host-fixAbsolutePathCheck branch June 16, 2025 18:19

This was referenced Jun 18, 2025

[release/9.0-staging] Fix absolute path check when loading hostfxr/hostpolicy/coreclr #116775

Merged

[release/8.0-staging] Fix absolute path check when loading hostfxr/hostpolicy/coreclr #116776

Merged

elinor-fung mentioned this pull request Jul 7, 2025

Make append_path in host utils a simple concatenation #117392

Merged

		@@ -342,6 +342,7 @@ namespace pal

		bool get_default_breadcrumb_store(string_t* recv);
		bool is_path_rooted(const string_t& path);

Fix absolute path check when loading hostfxr/hostpolicy/coreclr #116597

Fix absolute path check when loading hostfxr/hostpolicy/coreclr #116597

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