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style: Check that we do not insert more than MAX_GRID_LINE subgrid line name lists while constructing the list

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This helps avoid OOM with very large repeats.

Differential Revision: https://phabricator.services.mozilla.com/D161533
This commit is contained in:
Emily McDonough 2022-11-09 20:09:59 +00:00 • committed by Martin Robinson
parent e520c3796d
commit 8193fb3985
1 changed files with 23 additions and 12 deletions
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33
components/style/values/generics/grid.rs
View file

@ -669,6 +669,11 @@ impl Parse for LineNameList {
input.expect_ident_matching("subgrid")?;
let mut line_names = vec![];
let mut fill_data = None;
// Rather than truncating the result after inserting values, just
// have a maximum number of values. This gives us an early out on very
// large name lists, but more importantly prevents OOM on huge repeat
// expansions. (bug 1583429)
let mut max_remaining = MAX_GRID_LINE as usize;
loop {
let repeat_parse_result = input.try_parse(|input| {
@ -685,34 +690,40 @@ impl Parse for LineNameList {
})
});
if let Ok((names_list, count)) = repeat_parse_result {
let mut handle_size = |n| {
let n = cmp::min(n, max_remaining);
max_remaining -= n;
n
};
match count {
// FIXME(emilio): we shouldn't expand repeat() at
// parse time for subgrid. (bug 1583429)
RepeatCount::Number(num) => line_names.extend(
names_list
.iter()
.cloned()
.cycle()
.take(num.value() as usize * names_list.len()),
),
RepeatCount::Number(num) => {
let n = handle_size(
num.value() as usize * names_list.len());
line_names.extend(
names_list.iter().cloned().cycle().take(n));
},
RepeatCount::AutoFill if fill_data.is_none() => {
let fill_idx = line_names.len();
let fill_len = names_list.len();
fill_data = Some((fill_idx, fill_len));
line_names.extend(names_list.into_iter());
let n = handle_size(fill_len);
line_names.extend(names_list.into_iter().take(n));
},
_ => return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
}
} else if let Ok(names) = input.try_parse(parse_line_names) {
if max_remaining > 0 {
line_names.push(names);
max_remaining -= 1;
}
} else {
break;
}
}
if line_names.len() > MAX_GRID_LINE as usize {
line_names.truncate(MAX_GRID_LINE as usize);
}
debug_assert!(line_names.len() <= MAX_GRID_LINE as usize);
let (fill_start, fill_len) = fill_data.unwrap_or((0, 0));