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cp: refuse to copy symlink over itself #7729

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Merged
sylvestre merged 1 commit into from
Apr 28, 2025
Merged

cp: refuse to copy symlink over itself #7729

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8 changes: 7 additions & 1 deletion src/uu/cp/src/cp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1808,7 +1808,13 @@ fn is_forbidden_to_copy_to_same_file(
if options.copy_mode == CopyMode::SymLink && dest_is_symlink {
return false;
}
if dest_is_symlink && source_is_symlink && !options.dereference {
// If source and dest are both the same symlink but with different names, then allow the copy.
// This can occur, for example, if source and dest are both hardlinks to the same symlink.
if dest_is_symlink
&& source_is_symlink
&& source.file_name() != dest.file_name()
&& !options.dereference
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@dan-hipschman dan-hipschman Apr 11, 2025

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Note, if source and dest are both the same symlink but with different names, then the existing behavior (cp succeeds) is correct. This can occur, for example, if source and dest are both hardlinks to the same symlink. There's actually an existing unit test for this case.

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@sylvestre sylvestre Apr 12, 2025

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maybe add this as a comment in the code too ? :)

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@dan-hipschman dan-hipschman Apr 13, 2025

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Done

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@BenWiederhake BenWiederhake Apr 13, 2025

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"hardlinks to the same symlink" also sounds like something that we should include in the test suite, especially because this PR does NOT handle it correctly, despite your comment:

# Test setup
$ ln -s nonexistent bad
$ cp -P --link bad bad2
$ ls -1i bad bad2
20145169 bad
20145169 bad2

# GNU
$ cp -P bad bad2
$ ls -1i bad bad2
20145169 bad
20145169 bad2

# This PR (7677be2075a0401f05fdf9e138d821a5673f4404)
$ cargo run -q cp -P bad bad2
$ ls -1i bad bad2
20145169 bad
20178774 bad2

As you can see, the second file is no longer a hardlink of the first, even though it should still be.

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@dan-hipschman dan-hipschman Apr 13, 2025

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Thanks! Interesting test case. I looked into it and it seems related but separate from this PR (it occurs on main too BTW), so I made a separate PR for it: #7753

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@BenWiederhake BenWiederhake Apr 14, 2025

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Good call! I thought it's the same issue, sorry :D

{
return false;
}
true
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25 changes: 25 additions & 0 deletions tests/by-util/test_cp.rs
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Expand Up @@ -5217,6 +5217,31 @@ mod same_file {
assert_eq!(symlink1, at.resolve_link(symlink2));
}

#[test]
fn test_same_symlink_to_itself_no_dereference() {
let scene = TestScenario::new(util_name!());
let at = &scene.fixtures;
at.write(FILE_NAME, CONTENTS);
at.symlink_file(FILE_NAME, SYMLINK_NAME);
scene
.ucmd()
.args(&["-P", SYMLINK_NAME, SYMLINK_NAME])
.fails()
.stderr_contains("are the same file");
}

#[test]
fn test_same_dangling_symlink_to_itself_no_dereference() {
let scene = TestScenario::new(util_name!());
let at = &scene.fixtures;
at.symlink_file("nonexistent_file", SYMLINK_NAME);
scene
.ucmd()
.args(&["-P", SYMLINK_NAME, SYMLINK_NAME])
.fails()
.stderr_contains("are the same file");
}

// the following tests tries to copy file to a hardlink of the same file with
// various options
#[test]
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