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unexpand: prevent overflow on over-large tab stop values #14409

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unexpand: prevent overflow on over-large tab stop values #14409

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35 changes: 22 additions & 13 deletions src/uu/unexpand/src/unexpand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -375,12 +375,19 @@ fn write_tabs(
// We never turn a single space before a non-blank into
// a tab, unless it's at the start of the line.
let ai = print_state.leading || amode;
if (ai && print_state.pctype != CharType::Tab && print_state.col > print_state.scol + 1)
if (ai

@sylvestre sylvestre Sep 6, 2026

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this if is now too complex
could you please refactor it a bit ?

&& print_state.pctype != CharType::Tab
&& print_state.col > print_state.scol.saturating_add(1))
|| (print_state.col > print_state.scol
&& (print_state.leading || ai && print_state.pctype == CharType::Tab))
{
while let Some(nts) = next_tabstop(tab_config, print_state.scol) {
let target = print_state.scol + nts;
while print_state.scol < print_state.col {
let Some(nts) = next_tabstop(tab_config, print_state.scol) else {
break;
};
let Some(target) = print_state.scol.checked_add(nts) else {
break;
};
if print_state.col < target {
break;
}
Expand All @@ -389,7 +396,7 @@ fn write_tabs(
if print_state
.pending_wide
.iter()
.any(|&(start, width, _)| start < target && target < start + width)
.any(|&(start, width, _)| start < target && target < start.saturating_add(width))
{
break;
}
Expand All @@ -413,11 +420,11 @@ fn write_tabs(
{
let (_, width, bytes) = &print_state.pending_wide[wide_idx];
output.write_all(bytes)?;
print_state.scol += width;
print_state.scol = print_state.scol.saturating_add(*width);
wide_idx += 1;
} else {
output.write_all(b" ")?;
print_state.scol += 1;
print_state.scol = print_state.scol.saturating_add(1);
}
}
print_state.pending_wide.clear();
Expand Down Expand Up @@ -519,7 +526,7 @@ fn unexpand_buf(
{
write_tabs(output, tab_config, print_state, options.aflag)?;
print_state.scol = print_state.col;
print_state.col += buf.len();
print_state.col = print_state.col.saturating_add(buf.len());
output.write_all(buf)?;
return Ok(());
}
Expand All @@ -545,9 +552,9 @@ fn unexpand_buf(
let mut saw_tab = false;
while end < buf.len() {
match buf[end] {
b' ' => col += 1,
b' ' => col = col.saturating_add(1),
b'\t' => {
col += next_tabstop(tab_config, col).unwrap_or(1);
col = col.saturating_add(next_tabstop(tab_config, col).unwrap_or(1));
saw_tab = true;
}
_ => break,
Expand Down Expand Up @@ -602,10 +609,12 @@ fn unexpand_buf(
}

// compute next col, but only write space or tab chars if not buffering
print_state.col += if ctype == CharType::Space {
cwidth
print_state.col = if ctype == CharType::Space {
print_state.col.saturating_add(cwidth)
} else {
next_tabstop(tab_config, print_state.col).unwrap_or(1)
print_state
.col
.saturating_add(next_tabstop(tab_config, print_state.col).unwrap_or(1))
};

if !tabs_buffered {
Expand All @@ -619,7 +628,7 @@ fn unexpand_buf(
print_state.leading = false; // no longer at the start of a line
print_state.col = if ctype == CharType::Other {
// use computed width
print_state.col + cwidth
print_state.col.saturating_add(cwidth)
} else if print_state.col > 0 {
// Backspace case, but only if col > 0
print_state.col - 1
Expand Down
21 changes: 21 additions & 0 deletions tests/by-util/test_unexpand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -328,6 +328,27 @@ fn test_extended_tabstop_increment_overflow() {
.stderr_contains("tab stop value is too large");
}

#[test]
fn test_tabstop_near_max_does_not_overflow() {
new_ucmd!()
.arg(format!("-t{}", usize::MAX))
.pipe_in("a\tb")
.succeeds()
.stdout_is("a\tb");

new_ucmd!()
.arg(format!("-t{}", usize::MAX - 1))
.pipe_in("a\tb")
.succeeds()
.stdout_is("a\tb");

new_ucmd!()
.arg(format!("--tabs={}", usize::MAX))
.pipe_in(" a")
.succeeds()
.stdout_is(" a");
}

#[test]
fn test_is_directory() {
let (at, mut ucmd) = at_and_ucmd!();
Expand Down
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