On Sat, 30.11.13 10:45, Djalal Harouni (tix...@opendz.org) wrote: > Hi list, > > The sd_bus_error_copy() is used by bus clients to copy sd_bus_error > containt. If the 'need_free' field of the sd_bus_error struct of the > source is false, then strdup() will be avoided and the 'name' and > 'message' pointer fields of the destination are set to the sources's > fields. This will be true for all bus clients. > > An example: the libsystemd-bus/sd-bus.c:sd_bus_call() function is using > an sd_bus_message *incoming heap pointer inside the for() loop. > > If bus_read_message() succeed it will set the 'incoming' sd_bus_message > and if we have a match and the header type is an > SD_BUS_MESSAGE_METHOD_ERROR then sd_bus_error_copy() will get called to > copy the 'incoming->error' into the 'sd_bus_error *error' passed as an > argument to the sd_bus_call() function. Since 'incoming->error.need_free' > is false then destination's fields will be just set to source's fields. > > Memory pointed by source's fields may change at any time! There is no > guarentee that this memory will be available to be used or processed > later by the sd_bus_error destination. Even the 'incoming' memory will > be freed right after the sd_bus_error_copy() by sd_bus_message_unref() > and at this point, the 'error' data might be invalid > > I've experienced truncated error messsages, but not always! it is > related to lower layers and how bus messages are processed... > > Note: sd_bus_error_copy() behavior was to always strdup() source, it was > changed in part by commit 780896a4f1ec > > > Fix: > 1) make sd_bus_error_copy() always strdup content of source regardless > of the 'need_free' flag since it is never set. This will restore > behavior before commit 780896a4f1ec. This is the easy one. > > The following patch just use this one. > > > 2) Add a new sd_bus_error_strdup() API to force strdup() and make > sd_bus_error_copy() use it ? > > > I'm open to propostions, I can write another patch. Thanks!
Hmm, what we could do instead is store more information in sd_bus_error's need_free field: < 0 → temporarily const, deep copies necessary to keep around, no free() on free 0 → forever const, shallow copy OK, no free() on free > 0 → dynamic, deep copy always, free() on free I'll make the necessary changes! Thanks for the pointer! Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
