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Don't call rb_str_set_len while released the GVL. (#88)
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* Only release the GVL where necessary.

- Several string manipulation methods were invoked while the GVL was
  released. This is unsafe.
- The mutex protecting multi-threaded access was not covering buffer state
  manipulation, leading to data corruption and out-of-bounds writes.
- Using `rb_str_locktmp` prevents changes to buffer while it's in use.

[Bug #20863]
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@ioquatix
ioquatix authored Nov 20, 2024
1 parent 7bb6d98 commit e445cf3
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Showing 2 changed files with 176 additions and 118 deletions.
290 changes: 174 additions & 116 deletions ext/zlib/zlib.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -674,9 +674,7 @@ zstream_expand_buffer(struct zstream *z)
rb_obj_reveal(z->buf, rb_cString);
}

rb_mutex_unlock(z->mutex);
rb_protect(rb_yield, z->buf, &state);
rb_mutex_lock(z->mutex);
rb_protect(rb_yield, z->buf, &state);

if (ZSTREAM_REUSE_BUFFER_P(z)) {
rb_str_modify(z->buf);
Expand Down Expand Up @@ -720,15 +718,14 @@ zstream_expand_buffer_into(struct zstream *z, unsigned long size)
}
}

static void *
zstream_expand_buffer_protect(void *ptr)
static int
zstream_expand_buffer_protect(struct zstream *z)
{
struct zstream *z = (struct zstream *)ptr;
int state = 0;

rb_protect((VALUE (*)(VALUE))zstream_expand_buffer, (VALUE)z, &state);

return (void *)(VALUE)state;
return state;
}

static int
Expand Down Expand Up @@ -1023,57 +1020,14 @@ zstream_ensure_end(VALUE v)
}

static void *
zstream_run_func(void *ptr)
zstream_run_once(void *_arguments)
{
struct zstream_run_args *args = (struct zstream_run_args *)ptr;
int err, state, flush = args->flush;
struct zstream *z = args->z;
uInt n;

err = Z_OK;
while (!args->interrupt) {
n = z->stream.avail_out;
err = z->func->run(&z->stream, flush);
rb_str_set_len(z->buf, ZSTREAM_BUF_FILLED(z) + (n - z->stream.avail_out));

if (err == Z_STREAM_END) {
z->flags &= ~ZSTREAM_FLAG_IN_STREAM;
z->flags |= ZSTREAM_FLAG_FINISHED;
break;
}

if (err != Z_OK && err != Z_BUF_ERROR)
break;

if (z->stream.avail_out > 0) {
z->flags |= ZSTREAM_FLAG_IN_STREAM;
break;
}

if (z->stream.avail_in == 0 && z->func == &inflate_funcs) {
/* break here because inflate() return Z_BUF_ERROR when avail_in == 0. */
/* but deflate() could be called with avail_in == 0 (there's hidden buffer
in zstream->state) */
z->flags |= ZSTREAM_FLAG_IN_STREAM;
break;
}

if (args->stream_output) {
state = (int)(VALUE)rb_thread_call_with_gvl(zstream_expand_buffer_protect,
(void *)z);
}
else {
state = zstream_expand_buffer_non_stream(z);
}
struct zstream_run_args *arguments = (struct zstream_run_args *)_arguments;
struct zstream *z = arguments->z;

if (state) {
err = Z_OK; /* buffer expanded but stream processing was stopped */
args->jump_state = state;
break;
}
}
uintptr_t error = z->func->run(&z->stream, arguments->flush);

return (void *)(VALUE)err;
return (void*)error;
}

/*
Expand All @@ -1088,6 +1042,86 @@ zstream_unblock_func(void *ptr)
args->interrupt = 1;
}

static VALUE
zstream_run_once_begin(VALUE _arguments)
{
struct zstream_run_args *arguments = (struct zstream_run_args *)_arguments;
struct zstream *z = arguments->z;

rb_str_locktmp(z->buf);

#ifndef RB_NOGVL_UBF_ASYNC_SAFE
return (VALUE)rb_thread_call_without_gvl(zstream_run_once, (void *)arguments, zstream_unblock_func, (void *)arguments);
#else
return (VALUE)rb_nogvl(zstream_run_once, (void *)arguments, zstream_unblock_func, (void *)arguments, RB_NOGVL_UBF_ASYNC_SAFE);
#endif
}

static VALUE
zstream_run_once_ensure(VALUE _arguments)
{
struct zstream_run_args *arguments = (struct zstream_run_args *)_arguments;
struct zstream *z = arguments->z;

rb_str_unlocktmp(z->buf);

return Qnil;
}

static int
zstream_run_func(struct zstream_run_args *args)
{
struct zstream *z = args->z;
int state;
uInt n;

int err = Z_OK;
while (!args->interrupt) {
n = z->stream.avail_out;

err = (int)(VALUE)rb_ensure(zstream_run_once_begin, (VALUE)args, zstream_run_once_ensure, (VALUE)args);

rb_str_set_len(z->buf, ZSTREAM_BUF_FILLED(z) + (n - z->stream.avail_out));

if (err == Z_STREAM_END) {
z->flags &= ~ZSTREAM_FLAG_IN_STREAM;
z->flags |= ZSTREAM_FLAG_FINISHED;
break;
}

if (err != Z_OK && err != Z_BUF_ERROR)
break;

if (z->stream.avail_out > 0) {
z->flags |= ZSTREAM_FLAG_IN_STREAM;
break;
}

if (z->stream.avail_in == 0 && z->func == &inflate_funcs) {
/* break here because inflate() return Z_BUF_ERROR when avail_in == 0. */
/* but deflate() could be called with avail_in == 0 (there's hidden buffer
in zstream->state) */
z->flags |= ZSTREAM_FLAG_IN_STREAM;
break;
}

if (args->stream_output) {
state = zstream_expand_buffer_protect(z);
}
else {
state = zstream_expand_buffer_non_stream(z);
}

if (state) {
err = Z_OK; /* buffer expanded but stream processing was stopped */
args->jump_state = state;
break;
}
}

return err;
}

static VALUE
zstream_run_try(VALUE value_arg)
{
Expand Down Expand Up @@ -1126,14 +1160,7 @@ zstream_run_try(VALUE value_arg)
}

loop:
#ifndef RB_NOGVL_UBF_ASYNC_SAFE
err = (int)(VALUE)rb_thread_call_without_gvl(zstream_run_func, (void *)args,
zstream_unblock_func, (void *)args);
#else
err = (int)(VALUE)rb_nogvl(zstream_run_func, (void *)args,
zstream_unblock_func, (void *)args,
RB_NOGVL_UBF_ASYNC_SAFE);
#endif
err = zstream_run_func(args);

/* retry if no exception is thrown */
if (err == Z_OK && args->interrupt) {
Expand Down Expand Up @@ -1184,7 +1211,6 @@ zstream_run_ensure(VALUE value_arg)

/* Remove ZSTREAM_IN_PROGRESS flag to signal that this zstream is not in use. */
z->flags &= ~ZSTREAM_IN_PROGRESS;
rb_mutex_unlock(z->mutex);

return Qnil;
}
Expand All @@ -1201,7 +1227,7 @@ zstream_run(struct zstream *z, Bytef *src, long len, int flush)
.jump_state = 0,
.stream_output = !ZSTREAM_IS_GZFILE(z) && rb_block_given_p(),
};
rb_mutex_lock(z->mutex);

rb_ensure(zstream_run_try, (VALUE)&args, zstream_run_ensure, (VALUE)&args);
if (args.jump_state)
rb_jump_tag(args.jump_state);
Expand Down Expand Up @@ -1770,6 +1796,22 @@ do_deflate(struct zstream *z, VALUE src, int flush)
}
}

struct rb_zlib_deflate_arguments {
struct zstream *z;
VALUE src;
int flush;
};

static VALUE
rb_deflate_deflate_body(VALUE args)
{
struct rb_zlib_deflate_arguments *arguments = (struct rb_zlib_deflate_arguments *)args;

do_deflate(arguments->z, arguments->src, arguments->flush);

return zstream_detach_buffer(arguments->z);
}

/*
* Document-method: Zlib::Deflate#deflate
*
Expand Down Expand Up @@ -1801,11 +1843,10 @@ rb_deflate_deflate(int argc, VALUE *argv, VALUE obj)
{
struct zstream *z = get_zstream(obj);
VALUE src, flush;

rb_scan_args(argc, argv, "11", &src, &flush);
do_deflate(z, src, ARG_FLUSH(flush));
struct rb_zlib_deflate_arguments arguments = {z, src, ARG_FLUSH(flush)};

return zstream_detach_buffer(z);
return rb_mutex_synchronize(z->mutex, rb_deflate_deflate_body, (VALUE)&arguments);
}

/*
Expand Down Expand Up @@ -2101,56 +2142,19 @@ rb_inflate_add_dictionary(VALUE obj, VALUE dictionary)
return obj;
}

/*
* Document-method: Zlib::Inflate#inflate
*
* call-seq:
* inflate(deflate_string, buffer: nil) -> String
* inflate(deflate_string, buffer: nil) { |chunk| ... } -> nil
*
* Inputs +deflate_string+ into the inflate stream and returns the output from
* the stream. Calling this method, both the input and the output buffer of
* the stream are flushed. If string is +nil+, this method finishes the
* stream, just like Zlib::ZStream#finish.
*
* If a block is given consecutive inflated chunks from the +deflate_string+
* are yielded to the block and +nil+ is returned.
*
* If a :buffer keyword argument is given and not nil:
*
* * The :buffer keyword should be a String, and will used as the output buffer.
* Using this option can reuse the memory required during inflation.
* * When not passing a block, the return value will be the same object as the
* :buffer keyword argument.
* * When passing a block, the yielded chunks will be the same value as the
* :buffer keyword argument.
*
* Raises a Zlib::NeedDict exception if a preset dictionary is needed to
* decompress. Set the dictionary by Zlib::Inflate#set_dictionary and then
* call this method again with an empty string to flush the stream:
*
* inflater = Zlib::Inflate.new
*
* begin
* out = inflater.inflate compressed
* rescue Zlib::NeedDict
* # ensure the dictionary matches the stream's required dictionary
* raise unless inflater.adler == Zlib.adler32(dictionary)
*
* inflater.set_dictionary dictionary
* inflater.inflate ''
* end
*
* # ...
*
* inflater.close
*
* See also Zlib::Inflate.new
*/
struct rb_zlib_inflate_arguments {
struct zstream *z;
int argc;
VALUE *argv;
};

static VALUE
rb_inflate_inflate(int argc, VALUE* argv, VALUE obj)
rb_inflate_inflate_body(VALUE _arguments)
{
struct zstream *z = get_zstream(obj);
struct rb_zlib_inflate_arguments *arguments = (struct rb_zlib_inflate_arguments*)_arguments;
struct zstream *z = arguments->z;
int argc = arguments->argc;
VALUE *argv = arguments->argv;
VALUE dst, src, opts, buffer = Qnil;

if (OPTHASH_GIVEN_P(opts)) {
Expand Down Expand Up @@ -2205,6 +2209,60 @@ rb_inflate_inflate(int argc, VALUE* argv, VALUE obj)
return dst;
}

/*
* Document-method: Zlib::Inflate#inflate
*
* call-seq:
* inflate(deflate_string, buffer: nil) -> String
* inflate(deflate_string, buffer: nil) { |chunk| ... } -> nil
*
* Inputs +deflate_string+ into the inflate stream and returns the output from
* the stream. Calling this method, both the input and the output buffer of
* the stream are flushed. If string is +nil+, this method finishes the
* stream, just like Zlib::ZStream#finish.
*
* If a block is given consecutive inflated chunks from the +deflate_string+
* are yielded to the block and +nil+ is returned.
*
* If a :buffer keyword argument is given and not nil:
*
* * The :buffer keyword should be a String, and will used as the output buffer.
* Using this option can reuse the memory required during inflation.
* * When not passing a block, the return value will be the same object as the
* :buffer keyword argument.
* * When passing a block, the yielded chunks will be the same value as the
* :buffer keyword argument.
*
* Raises a Zlib::NeedDict exception if a preset dictionary is needed to
* decompress. Set the dictionary by Zlib::Inflate#set_dictionary and then
* call this method again with an empty string to flush the stream:
*
* inflater = Zlib::Inflate.new
*
* begin
* out = inflater.inflate compressed
* rescue Zlib::NeedDict
* # ensure the dictionary matches the stream's required dictionary
* raise unless inflater.adler == Zlib.adler32(dictionary)
*
* inflater.set_dictionary dictionary
* inflater.inflate ''
* end
*
* # ...
*
* inflater.close
*
* See also Zlib::Inflate.new
*/
static VALUE
rb_inflate_inflate(int argc, VALUE* argv, VALUE obj)
{
struct zstream *z = get_zstream(obj);
struct rb_zlib_inflate_arguments arguments = {z, argc, argv};
return rb_mutex_synchronize(z->mutex, rb_inflate_inflate_body, (VALUE)&arguments);
}

/*
* call-seq: << string
*
Expand Down
4 changes: 2 additions & 2 deletions test/zlib/test_zlib.rb
View file
Original file line number Diff line number Diff line change
Expand Up @@ -545,7 +545,7 @@ def test_recursive_deflate
zd = Zlib::Deflate.new

s = SecureRandom.random_bytes(1024**2)
assert_raise(Zlib::InProgressError) do
assert_raise(ThreadError) do
zd.deflate(s) do
zd.deflate(s)
end
Expand All @@ -563,7 +563,7 @@ def test_recursive_inflate

s = Zlib.deflate(SecureRandom.random_bytes(1024**2))

assert_raise(Zlib::InProgressError) do
assert_raise(ThreadError) do
zi.inflate(s) do
zi.inflate(s)
end
Expand Down

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