On Wed, Apr 22, 2020 at 03:46:26AM +0100, Al Viro wrote: > > Better allocate count + 1 bytes here, that way a lot of insanity in the > > instances can be simply converted to snprintf(). Yes, I know it'll bring > > the Church Of Avoiding The Abomination Of Sprintf out of the woodwork, > > but... > > FWIW, consider e.g. net/sunrpc/sysctl.c: > > Nevermind that the read side should be simply > int err = proc_douintvec(table, write, buffer, lenp, ppos); > /* Display the RPC tasks on writing to rpc_debug */ > if (!err && strcmp(table->procname, "rpc_debug") == 0) > rpc_show_tasks(&init_net); > return err; > the write side would become > len = snprintf(buffer, *lenp + 1, "0x%04x\n", > *(unsigned int *)table->data); > if (len > *lenp) > len = *lenp; > *lenp -= len; > *ppos += len; > return 0; > and I really wonder if lifting the trailing boilerplate into the caller would've > been better. Note that e.g. gems like > if (!first) > err = proc_put_char(&buffer, &left, '\t'); > if (err) > break; > err = proc_put_long(&buffer, &left, lval, neg); > if (err) > break; > are due to lack of snprintf-to-user; now, lose the "to user" part and we suddenly > can be rid of that stuff... That sounds pretty sensible, but can we do that as an extra step? That is in merge window N just move to passing kernel pointers, check for fall out. In merge window N + 1 start allocatin the extra byte and switch at least the common helpers for snprintf?
