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content_encoding: use writer struct subclasses for different encodings

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The variable-sized encoding-specific storage of a struct contenc_writer
currently relies on void * alignment that may be insufficient with
regards to the specific storage fields, although having not caused any
problems yet.

In addition, gcc 11.3 issues a warning on access to fields of partially
allocated structures that can occur when the specific storage size is 0:

  content_encoding.c: In function ‘Curl_build_unencoding_stack’:
  content_encoding.c:980:21: warning: array subscript ‘struct contenc_writer[0]’ is partly outside array bounds of ‘unsigned char[16]’ [-Warray-bounds]
    980 |     writer->handler = handler;
        |     ~~~~~~~~~~~~~~~~^~~~~~~~~
  In file included from content_encoding.c:49:
  memdebug.h:115:29: note: referencing an object of size 16 allocated by ‘curl_dbg_calloc’
    115 | #define calloc(nbelem,size) curl_dbg_calloc(nbelem, size, __LINE__, __FILE__)
        |                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  content_encoding.c:977:60: note: in expansion of macro ‘calloc’
    977 |   struct contenc_writer *writer = (struct contenc_writer *)calloc(1, sz);

To solve both these problems, the current commit replaces the
contenc_writer/params structure pairs by "subclasses" of struct
contenc_writer. These are structures that contain a contenc_writer at
offset 0. Proper field alignment is therefore handled by the compiler and
full structure allocation is performed, silencing the warnings.

Closes #9455
This commit is contained in:
Patrick Monnerat 2022-09-09 13:25:02 +02:00 committed by Daniel Stenberg
parent ae4d1437f1
commit 4399b0303a
No known key found for this signature in database
GPG Key ID: 5CC908FDB71E12C2
2 changed files with 38 additions and 31 deletions
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66
lib/content_encoding.c
View File

@ -82,8 +82,9 @@ typedef enum {
ZLIB_INIT_GZIP /* initialized in transparent gzip mode */
} zlibInitState;
/* Writer parameters. */
struct zlib_params {
/* Deflate and gzip writer. */
struct zlib_writer {
struct contenc_writer super;
zlibInitState zlib_init; /* zlib init state */
uInt trailerlen; /* Remaining trailer byte count. */
z_stream z; /* State structure for zlib. */
@ -135,7 +136,7 @@ exit_zlib(struct Curl_easy *data,
}
static CURLcode process_trailer(struct Curl_easy *data,
struct zlib_params *zp)
struct zlib_writer *zp)
{
z_stream *z = &zp->z;
CURLcode result = CURLE_OK;
@ -162,7 +163,7 @@ static CURLcode inflate_stream(struct Curl_easy *data,
struct contenc_writer *writer,
zlibInitState started)
{
struct zlib_params *zp = (struct zlib_params *) &writer->params;
struct zlib_writer *zp = (struct zlib_writer *) writer;
z_stream *z = &zp->z; /* zlib state structure */
uInt nread = z->avail_in;
Bytef *orig_in = z->next_in;
@ -265,7 +266,7 @@ static CURLcode inflate_stream(struct Curl_easy *data,
static CURLcode deflate_init_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct zlib_params *zp = (struct zlib_params *) &writer->params;
struct zlib_writer *zp = (struct zlib_writer *) writer;
z_stream *z = &zp->z; /* zlib state structure */
if(!writer->downstream)
@ -285,7 +286,7 @@ static CURLcode deflate_unencode_write(struct Curl_easy *data,
struct contenc_writer *writer,
const char *buf, size_t nbytes)
{
struct zlib_params *zp = (struct zlib_params *) &writer->params;
struct zlib_writer *zp = (struct zlib_writer *) writer;
z_stream *z = &zp->z; /* zlib state structure */
/* Set the compressed input when this function is called */
@ -302,7 +303,7 @@ static CURLcode deflate_unencode_write(struct Curl_easy *data,
static void deflate_close_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct zlib_params *zp = (struct zlib_params *) &writer->params;
struct zlib_writer *zp = (struct zlib_writer *) writer;
z_stream *z = &zp->z; /* zlib state structure */
exit_zlib(data, z, &zp->zlib_init, CURLE_OK);
@ -314,7 +315,7 @@ static const struct content_encoding deflate_encoding = {
deflate_init_writer,
deflate_unencode_write,
deflate_close_writer,
sizeof(struct zlib_params)
sizeof(struct zlib_writer)
};
@ -322,7 +323,7 @@ static const struct content_encoding deflate_encoding = {
static CURLcode gzip_init_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct zlib_params *zp = (struct zlib_params *) &writer->params;
struct zlib_writer *zp = (struct zlib_writer *) writer;
z_stream *z = &zp->z; /* zlib state structure */
if(!writer->downstream)
@ -439,7 +440,7 @@ static CURLcode gzip_unencode_write(struct Curl_easy *data,
struct contenc_writer *writer,
const char *buf, size_t nbytes)
{
struct zlib_params *zp = (struct zlib_params *) &writer->params;
struct zlib_writer *zp = (struct zlib_writer *) writer;
z_stream *z = &zp->z; /* zlib state structure */
if(zp->zlib_init == ZLIB_INIT_GZIP) {
@ -566,7 +567,7 @@ static CURLcode gzip_unencode_write(struct Curl_easy *data,
static void gzip_close_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct zlib_params *zp = (struct zlib_params *) &writer->params;
struct zlib_writer *zp = (struct zlib_writer *) writer;
z_stream *z = &zp->z; /* zlib state structure */
exit_zlib(data, z, &zp->zlib_init, CURLE_OK);
@ -578,15 +579,16 @@ static const struct content_encoding gzip_encoding = {
gzip_init_writer,
gzip_unencode_write,
gzip_close_writer,
sizeof(struct zlib_params)
sizeof(struct zlib_writer)
};
#endif /* HAVE_LIBZ */
#ifdef HAVE_BROTLI
/* Writer parameters. */
struct brotli_params {
/* Brotli writer. */
struct brotli_writer {
struct contenc_writer super;
BrotliDecoderState *br; /* State structure for brotli. */
};
@ -631,7 +633,7 @@ static CURLcode brotli_map_error(BrotliDecoderErrorCode be)
static CURLcode brotli_init_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct brotli_params *bp = (struct brotli_params *) &writer->params;
struct brotli_writer *bp = (struct brotli_writer *) writer;
(void) data;
if(!writer->downstream)
@ -645,7 +647,7 @@ static CURLcode brotli_unencode_write(struct Curl_easy *data,
struct contenc_writer *writer,
const char *buf, size_t nbytes)
{
struct brotli_params *bp = (struct brotli_params *) &writer->params;
struct brotli_writer *bp = (struct brotli_writer *) writer;
const uint8_t *src = (const uint8_t *) buf;
char *decomp;
uint8_t *dst;
@ -692,7 +694,8 @@ static CURLcode brotli_unencode_write(struct Curl_easy *data,
static void brotli_close_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct brotli_params *bp = (struct brotli_params *) &writer->params;
struct brotli_writer *bp = (struct brotli_writer *) writer;
(void) data;
if(bp->br) {
@ -707,14 +710,15 @@ static const struct content_encoding brotli_encoding = {
brotli_init_writer,
brotli_unencode_write,
brotli_close_writer,
sizeof(struct brotli_params)
sizeof(struct brotli_writer)
};
#endif
#ifdef HAVE_ZSTD
/* Writer parameters. */
struct zstd_params {
/* Zstd writer. */
struct zstd_writer {
struct contenc_writer super;
ZSTD_DStream *zds; /* State structure for zstd. */
void *decomp;
};
@ -722,7 +726,8 @@ struct zstd_params {
static CURLcode zstd_init_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct zstd_params *zp = (struct zstd_params *)&writer->params;
struct zstd_writer *zp = (struct zstd_writer *) writer;
(void)data;
if(!writer->downstream)
@ -738,7 +743,7 @@ static CURLcode zstd_unencode_write(struct Curl_easy *data,
const char *buf, size_t nbytes)
{
CURLcode result = CURLE_OK;
struct zstd_params *zp = (struct zstd_params *)&writer->params;
struct zstd_writer *zp = (struct zstd_writer *) writer;
ZSTD_inBuffer in;
ZSTD_outBuffer out;
size_t errorCode;
@ -777,7 +782,8 @@ static CURLcode zstd_unencode_write(struct Curl_easy *data,
static void zstd_close_writer(struct Curl_easy *data,
struct contenc_writer *writer)
{
struct zstd_params *zp = (struct zstd_params *)&writer->params;
struct zstd_writer *zp = (struct zstd_writer *) writer;
(void)data;
if(zp->decomp) {
@ -796,7 +802,7 @@ static const struct content_encoding zstd_encoding = {
zstd_init_writer,
zstd_unencode_write,
zstd_close_writer,
sizeof(struct zstd_params)
sizeof(struct zstd_writer)
};
#endif
@ -829,7 +835,7 @@ static const struct content_encoding identity_encoding = {
identity_init_writer,
identity_unencode_write,
identity_close_writer,
0
sizeof(struct contenc_writer)
};
@ -921,7 +927,7 @@ static const struct content_encoding client_encoding = {
client_init_writer,
client_unencode_write,
client_close_writer,
0
sizeof(struct contenc_writer)
};
@ -964,7 +970,7 @@ static const struct content_encoding error_encoding = {
error_init_writer,
error_unencode_write,
error_close_writer,
0
sizeof(struct contenc_writer)
};
/* Create an unencoding writer stage using the given handler. */
@ -973,8 +979,10 @@ new_unencoding_writer(struct Curl_easy *data,
const struct content_encoding *handler,
struct contenc_writer *downstream)
{
size_t sz = offsetof(struct contenc_writer, params) + handler->paramsize;
struct contenc_writer *writer = (struct contenc_writer *)calloc(1, sz);
struct contenc_writer *writer;
DEBUGASSERT(handler->writersize >= sizeof(struct contenc_writer));
writer = (struct contenc_writer *) calloc(1, handler->writersize);
if(writer) {
writer->handler = handler;

3
lib/content_encoding.h
View File

@ -28,7 +28,6 @@
struct contenc_writer {
const struct content_encoding *handler; /* Encoding handler. */
struct contenc_writer *downstream; /* Downstream writer. */
void *params; /* Encoding-specific storage (variable length). */
};
/* Content encoding writer. */
@ -42,7 +41,7 @@ struct content_encoding {
const char *buf, size_t nbytes);
void (*close_writer)(struct Curl_easy *data,
struct contenc_writer *writer);
size_t paramsize;
size_t writersize;
};