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buffer: do not affect memory after target for utf16 write

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Do not write one character too much before shifting the whole result
to the left when using UTF16-LE, possibly overwriting already-used
memory while doing so.

Fixes: https://github.com/nodejs/node/issues/26422

PR-URL: https://github.com/nodejs/node/pull/26432
Fixes: https://github.com/nodejs/node/issues/26422
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
This commit is contained in:
Anna Henningsen 2019-03-04 17:17:05 +01:00 committed by Ruben Bridgewater
parent ceb73e714a
commit 31147c4704
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GPG Key ID: F07496B3EB3C1762
2 changed files with 14 additions and 5 deletions
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11
src/string_bytes.cc
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@ -287,18 +287,19 @@ size_t StringBytes::WriteUCS2(Isolate* isolate,
CHECK_EQ(reinterpret_cast<uintptr_t>(aligned_dst) % sizeof(*dst), 0);
// Write all but the last char
max_chars = std::min(max_chars, static_cast<size_t>(str->Length()));
if (max_chars == 0) return 0;
nchars = str->Write(isolate, aligned_dst, 0, max_chars - 1, flags);
CHECK_EQ(nchars, max_chars - 1);
// Shift everything to unaligned-left
memmove(dst, aligned_dst, nchars * sizeof(*dst));
// One more char to be written
uint16_t last;
if (nchars == max_chars - 1 &&
str->Write(isolate, &last, nchars, 1, flags) != 0) {
memcpy(buf + nchars * sizeof(*dst), &last, sizeof(last));
nchars++;
}
CHECK_EQ(str->Write(isolate, &last, nchars, 1, flags), 1);
memcpy(buf + nchars * sizeof(*dst), &last, sizeof(last));
nchars++;
*chars_written = nchars;
return nchars * sizeof(*dst);

8
test/parallel/test-buffer-write.js
View File

@ -91,3 +91,11 @@ assert.strictEqual(Buffer.compare(z, Buffer.alloc(4, 0)), 0);
// Large overrun could corrupt the process
assert.strictEqual(Buffer.alloc(4)
.write('ыыыыыы'.repeat(100), 3, 'utf16le'), 0);
{
// .write() does not affect the byte after the written-to slice of the Buffer.
// Refs: https://github.com/nodejs/node/issues/26422
const buf = Buffer.alloc(8);
assert.strictEqual(buf.write('ыы', 1, 'utf16le'), 4);
assert.deepStrictEqual([...buf], [0, 0x4b, 0x04, 0x4b, 0x04, 0, 0, 0]);
}