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Reject older versions of PipeWire than built against

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Newer versions of PipeWire may add things to public structures. For example,
pw_buffer::requested added in 0.3.49. Building against 0.3.49 or newer, but
then running with 0.3.48 could result in invalid accesses since the returned
pw_buffer objects are shorter than the definition says to expect, creating
undefined behavior. Even if explicit access to the additional fields is
protected by a runtime check, the language allows the compiler to assume a
pointer to a pw_buffer object contains a complete pw_buffer, allowing the
optimizer to access the field earlier than the check (with the check only
controlling if the value gets used).

Another example is pw_time, which had a few fields added in 0.3.50 along with a
function, pw_stream_get_time_n, that provides the size of the pw_time struct
the application is using (so the library knows what version of the struct it
has to fill in). If a later version adds a new field, running it with an older
version will either fail (due to the library getting a size larger than it
knows about) or silently leave the newer fields as garbage.
This commit is contained in:
Chris Robinson 2022-05-07 07:58:48 -07:00
parent 10e863d1b4
commit 96756acc52
1 changed files with 24 additions and 0 deletions
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24
alc/backends/pipewire.cpp
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@ -115,12 +115,26 @@ constexpr char pwireDevice[] = "PipeWire Output";
constexpr char pwireInput[] = "PipeWire Input";
bool check_version(const char *version)
{
/* There doesn't seem to be a function to get the version as an integer, so
* instead we have to parse the string, which hopefully won't break in the
* future.
*/
int major{0}, minor{0}, revision{0};
int ret{sscanf(version, "%d.%d.%d", &major, &minor, &revision)};
if(ret == 3 && PW_CHECK_VERSION(major, minor, revision))
return true;
return false;
}
#ifdef HAVE_DYNLOAD
#define PWIRE_FUNCS(MAGIC) \
MAGIC(pw_context_connect) \
MAGIC(pw_context_destroy) \
MAGIC(pw_context_new) \
MAGIC(pw_core_disconnect) \
MAGIC(pw_get_library_version) \
MAGIC(pw_init) \
MAGIC(pw_properties_free) \
MAGIC(pw_properties_new) \
@ -199,6 +213,7 @@ bool pwire_load()
#define pw_context_destroy ppw_context_destroy
#define pw_context_new ppw_context_new
#define pw_core_disconnect ppw_core_disconnect
#define pw_get_library_version ppw_get_library_version
#define pw_init ppw_init
#define pw_properties_free ppw_properties_free
#define pw_properties_new ppw_properties_new
@ -1930,6 +1945,15 @@ bool PipeWireBackendFactory::init()
if(!pwire_load())
return false;
const char *version{pw_get_library_version()};
if(!check_version(version))
{
WARN("PipeWire version \"%s\" too old (%s or newer required)\n", version,
pw_get_headers_version());
return false;
}
TRACE("Found PipeWire version \"%s\" (%s or newer)\n", version, pw_get_headers_version());
pw_init(0, nullptr);
if(!gEventHandler.init())
return false;