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Fix out-of-bounds read in gets with a limit inside a truncated character #233

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Fix out-of-bounds read in gets with a limit inside a truncated character #233

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3 changes: 2 additions & 1 deletion ext/java/org/jruby/ext/stringio/StringIO.java
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Original file line number Diff line number Diff line change
Expand Up @@ -896,7 +896,8 @@ private IRubyObject getline(ThreadContext context, final IRubyObject rs, int lim
int w = 0;

if (limit > 0 && s + limit < e) {
e = getEncoding().rightAdjustCharHead(stringBytes, s, s + limit, e);
// a fixed-width encoding may step past a truncated last character
e = Math.min(e, getEncoding().rightAdjustCharHead(stringBytes, s, s + limit, e));
}
if (rs == context.nil) {
if (chomp) {
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3 changes: 3 additions & 0 deletions ext/stringio/stringio.c
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Expand Up @@ -1555,7 +1555,10 @@ strio_getline(struct getline_arg *arg, struct StringIO *ptr)
e = s + RSTRING_LEN(ptr->string);
s += ptr->pos;
if (limit > 0 && (size_t)limit < (size_t)(e - s)) {
const char *const end = e;
e = rb_enc_right_char_head(s, s + limit, e, get_enc(ptr));
/* a fixed-width encoding may step past a truncated last character */
if (e > end) e = end;
}
if (NIL_P(str)) {
if (arg->chomp) {
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11 changes: 11 additions & 0 deletions test/stringio/test_stringio.rb
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Expand Up @@ -151,6 +151,17 @@ def test_gets_utf_16
assert_nil(stringio.gets)
end

def test_gets_limit_in_truncated_fixed_width_char
# 6 bytes: one UTF-32 code unit and a truncated one. The limit
# falls inside the truncated unit, and the line must stop at the
# end of the string, not beyond it.
stringio = StringIO.new("abcdef".b.freeze)
stringio.set_encoding(Encoding::UTF_32LE)
assert_equal("abcdef".b, stringio.gets(5).b)
assert_equal(6, stringio.pos)
assert_nil(stringio.gets(5))
end

def test_gets_chomp
assert_equal(nil, StringIO.new("").gets(chomp: true))
assert_equal("", StringIO.new("\n").gets(chomp: true))
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