fix: util/path: CheckSystemDriveAndRemoveDriveLetter to preserve /

[profnandaa]

The call to CheckSystemDriveAndRemoveDriveLetter() does not preserve the trailing / or \\. This happens because filepath.Clean() strips away any trailing slashes. For example /sample/ will be \\sample on Windows. This function was mainly written for Windows scenarios, which have System Drive Letters like C:/, etc.

This was causing cases like COPY testfile /testdir/ to be intepreted as COPY testfile /testdir, and if testdir is not explictly created before the call, it ends up being treated as a destination file other than a directory.

Fix this by checking that if we have a trailing / or \\, we preserve it after the call to filepath.Clean().

Fixes #5249

PS.

Also fixed for cross-building Windows from Linux, that would fail silently:

Repro dockerfile without RUN:

FROM mcr.microsoft.com/windows/nanoserver:ltsc2022
COPY test1.txt /sample/
#RUN type \sample\test1.txt

Build log:

$ docker buildx build --platform windows/amd64 `
    --builder buildkitd-dev --no-cache --tag=windows-test . `
    --progress plain `
    --output type=local,dest=./output

#6 [2/2] COPY test1.txt /sample/
#6 DONE 0.1s

#7 exporting to client directory
#7 copying files 31B
#7 copying files 230.88MB 0.8s done
#7 DONE 0.8s

Checking results, sample is a file instead of a directory:

# before
$ ls -l output/sample
-rw-r--r-- 1 root root 6 Sep 24 08:57 output/sample

# after
$ ls -l output/sample
total 4
-rw-r--r-- 1 root root 6 Sep 24 08:57 test1.txt

NOTE: also covered cases like, where platform-specific filepath.Clean() won't strip out the \\ on Linux:

COPY test1.txt \\sample\\

[profnandaa]

Looking into the CI failures...

[profnandaa]

Found the regression caused by this, thankfully coz of the checked in integration tests!

Dockerfile:

FROM mcr.microsoft.com/windows/nanoserver:ltsc2022
COPY test1.txt /sample/
RUN type \sample\test1.txt

COPY test1.txt /
COPY test1.txt /test2.txt

RUN type test1.txt
RUN type test2.txt

Build log:

Dockerfile:5
--------------------
   3 |     RUN type \sample\test1.txt
   4 |     
   5 | >>> COPY test1.txt /
   6 |     COPY test1.txt /test2.txt
   7 |     
--------------------
error: failed to solve: removing drive letter: UNC paths are not supported
Process 5812 has exited with status 1

Fixing.

[profnandaa]

CI failure seems unrelated?

=== FAIL: client TestClientGatewayIntegration/TestClientGatewayContainerHostNetworkingValidation/worker=containerd/netmode=host (0.97s)
    build_test.go:2133: 
        	Error Trace:	/src/client/build_test.go:2133
        	            				/src/client/build_test.go:2031
        	            				/src/util/testutil/integration/run.go:97
        	            				/src/util/testutil/integration/run.go:211
        	Error:      	Received unexpected error:
        	            	expecting started message, got *moby_buildkit_v1_frontend.ExecMessage_Exit

[profnandaa]

PTAL again, addressed the comments. @tonistiigi @gabriel-samfira

[gabriel-samfira]

LGTM. Waiting for a second review before merging.

[profnandaa]

Thanks!

…

On Wed, Oct 9, 2024, 12:28 Gabriel ***@***.***> wrote: LGTM. Waiting for a second review before merging. — Reply to this email directly, view it on GitHub <#5317 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAB7ZEMYKEKKZE5GDTAXVQLZ2TZKPAVCNFSM6AAAAABN6FHHEWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDIMBRHAYDSOBYGI> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[profnandaa]

@crazy-max @tonistiigi -- can take a look at this one?