I did a search for code doing s[n]printf(buf, "...", ..., buf, ...)
and found a few instances. They all do it with the format string beginning with "%s" and buf being passed as the corresponding parameter (obviously to append to the existing string). That works (AFAICT), both with the current printf implementation and with the string() modification which is now in -mm. It would obviously go horribly wrong if anything, even non-specifiers, precede the "%s" in the format string. The question is, do we want to officially support this particular case of overlapping src and dst? Or should we close our eyes and hope it will continue to work [1] and that it won't cause a caffeine-deprived hacker to accidentally think one could also prepend to a buffer by doing sprintf(buf, "...%s", ..., buf)? I'm actually surprised gcc doesn't warn about this. [1] Not that I can immediately think of a sane way to implement snprintf where it won't work, but you never know... My coccinelle-fu isn't sufficient to find cases where one of the buf instances is a more complicated expressions involving buf as a subexpression, as in s[n]printf(buf, "...", ..., buf + 4, ...) or s[n]printf(&buf[len], "...", ..., buf, ...) which would presumably always be wrong. Julia? Rasmus The cases I've found are ./drivers/gpu/drm/amd/amdkfd/kfd_topology.c:613:53-54: s[n]printf, overlapping source and destination buffers ./drivers/gpu/drm/amd/amdkfd/kfd_topology.c:618:16-17: s[n]printf, overlapping source and destination buffers ./drivers/gpu/drm/amd/amdkfd/kfd_topology.c:488:58-59: s[n]printf, overlapping source and destination buffers ./drivers/input/joystick/analog.c:445:59-60: s[n]printf, overlapping source and destination buffers ./drivers/leds/led-class-flash.c:215:32-33: s[n]printf, overlapping source and destination buffers ./drivers/media/pci/zoran/videocodec.c:120:39-40: s[n]printf, overlapping source and destination buffers ./drivers/media/rc/ati_remote.c:875:47-48: s[n]printf, overlapping source and destination buffers ./drivers/net/wireless/ti/wlcore/boot.c:125:24-25: s[n]printf, overlapping source and destination buffers ./drivers/net/wireless/ti/wlcore/boot.c:128:37-38: s[n]printf, overlapping source and destination buffers ./drivers/usb/atm/usbatm.c:1341:46-47: s[n]printf, overlapping source and destination buffers -- 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/
