I'm planning to convert task_struct->comm to use RCU so that they always get
consistent result. Inconsistent result (e.g. trailing '\0' byte is emitted when
printing string argument) is caused by breaking a rule that the string argument
must not change during the function when it is passed as "const char *" (e.g.
strcmp() and printf("%s")).Although task_struct->comm is not modified so frequently, task_struct->comm passed as a "const char *" argument can change at any moment unless we pass task_struct->comm via get_task_comm(). Since there are a lot of current->comm readers, Andrew Morton suggested that we might be able to omit passing the argument and I wrote a patch that adds a second format-start character for omit passing the argument. Kees Cook wrote: > I'm on board with the idea of embedding comm/pid/whatever, but I > either missed or do not understand why a second format-start character > is being added. I think this will complicate audits and maybe trigger > weird info leaks (imagine printing a string that was %-escaped, but > not 0x1A-escaped?) The second format-start character applies to only format string. If we use a dynamically generated string that was %-escaped at run-time as a format string, we will leak globally accessible variables. But are there such users? Such users are rare because they are already problematic since compilers cannot check for safety using __printf() attributes at build-time. > Hrmpf. Yeah, on the fence about this. But I'm fine even if we cannot agree with the second format-start character. Since my purpose is to make reading of task_struct->comm consistent, %pT-like extension is what I want for centralizing pointer dereferences. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
