On 12/16/21 15:11, Alex Bennée wrote: > Philippe Mathieu-Daudé <phi...@redhat.com> writes: > >> When experimenting raising GLIB_VERSION_MIN_REQUIRED to 2.68 >> (Fedora 34 provides GLib 2.68.1) we get: >> >> hw/virtio/virtio-crypto.c:245:24: error: 'g_memdup' is deprecated: Use >> 'g_memdup2' instead [-Werror,-Wdeprecated-declarations] >> ... >> >> g_memdup() has been updated by g_memdup2() to fix eventual security >> issues (size argument is 32-bit and could be truncated / wrapping). >> GLib recommends to copy their static inline version of g_memdup2(): >> https://discourse.gnome.org/t/port-your-module-from-g-memdup-to-g-memdup2-now/5538 >> >> Our glib-compat.h provides a comment explaining how to deal with >> these deprecated declarations (see commit e71e8cc0355 >> "glib: enforce the minimum required version and warn about old APIs"). >> >> Following this comment suggestion, implement the g_memdup2_qemu() >> wrapper to g_memdup2(), and use the safer equivalent inlined when >> we are using pre-2.68 GLib. >> >> Reported-by: Eric Blake <ebl...@redhat.com> >> Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com> >> --- >> include/glib-compat.h | 37 +++++++++++++++++++++++++++++++++++++ >> 1 file changed, 37 insertions(+) >> >> diff --git a/include/glib-compat.h b/include/glib-compat.h >> index 9e95c888f54..8d01a8c01fb 100644 >> --- a/include/glib-compat.h >> +++ b/include/glib-compat.h >> @@ -68,6 +68,43 @@ >> * without generating warnings. >> */ >> >> +/* >> + * g_memdup2_qemu: >> + * @mem: (nullable): the memory to copy. >> + * @byte_size: the number of bytes to copy. >> + * >> + * Allocates @byte_size bytes of memory, and copies @byte_size bytes into it >> + * from @mem. If @mem is %NULL it returns %NULL. >> + * >> + * This replaces g_memdup(), which was prone to integer overflows when >> + * converting the argument from a #gsize to a #guint. >> + * >> + * This static inline version is a backport of the new public API from >> + * GLib 2.68, kept internal to GLib for backport to older stable releases. >> + * See https://gitlab.gnome.org/GNOME/glib/-/issues/2319. >> + * >> + * Returns: (nullable): a pointer to the newly-allocated copy of the memory, >> + * or %NULL if @mem is %NULL. >> + */ >> +static inline gpointer g_memdup2_qemu(gconstpointer mem, gsize byte_size) >> +{ >> +#if GLIB_CHECK_VERSION(2, 68, 0) >> + return g_memdup2(mem, byte_size); >> +#else >> + gpointer new_mem; >> + >> + if (mem && byte_size != 0) { >> + new_mem = g_malloc(byte_size); >> + memcpy(new_mem, mem, byte_size); >> + } else { >> + new_mem = NULL; >> + } >> + >> + return new_mem; >> +#endif >> +} >> +#define g_memdup2(m, s) g_memdup2_qemu(m, s) >> + > > As per our style wouldn't it make sense to just call it qemu_memdup(m, > s)?
I followed the documentation in include/glib-compat.h: /* * Note that because of the GLIB_VERSION_MAX_ALLOWED constant above, allowing * use of functions from newer GLib via this compat header needs a little * trickery to prevent warnings being emitted. * * Consider a function from newer glib-X.Y that we want to use * * int g_foo(const char *wibble) * * We must define a static inline function with the same signature that does * what we need, but with a "_qemu" suffix e.g. * * static inline void g_foo_qemu(const char *wibble) * { * #if GLIB_CHECK_VERSION(X, Y, 0) * g_foo(wibble) * #else * g_something_equivalent_in_older_glib(wibble); * #endif * } * * The #pragma at the top of this file turns off -Wdeprecated-declarations, * ensuring this wrapper function impl doesn't trigger the compiler warning * about using too new glib APIs. Finally we can do * * #define g_foo(a) g_foo_qemu(a) * * So now the code elsewhere in QEMU, which *does* have the * -Wdeprecated-declarations warning active, can call g_foo(...) as normal, * without generating warnings. */ which is how g_unix_get_passwd_entry_qemu() is implemented. Should we reword the documentation first?