In the Linux kernel, the following vulnerability has been resolved:
block/rnbd-srv: Check for unlikely string overflow
Since dev_search_path can technically be as large as PATH_MAX, there was a risk of truncation when copying it and a second string into full_path since it was also PATH_MAX sized. The W=1 builds were reporting this warning:
drivers/block/rnbd/rnbd-srv.c: In function process_msg_open.isra: drivers/block/rnbd/rnbd-srv.c:616:51: warning: %s directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095 [-Wformat-truncation=] 616 | snprintf(full_path, PATH_MAX, %s/%s, | ^~ In function rnbd_srv_get_full_path, inlined from process_msg_open.isra at drivers/block/rnbd/rnbd-srv.c:721:14: drivers/block/rnbd/rnbd-srv.c:616:17: note: snprintf output between 2 and 4351 bytes into a destination of size 4096 616 | snprintf(full_path, PATH_MAX, %s/%s, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 617 | dev_search_path, dev_name); | ~~~~~~~~~~~~~~~~~~~~~~~~~~
To fix this, unconditionally check for truncation (as was already done for the case where %SESSNAME% was present).