From: Steev Klimaszewski Date: Sat, 17 Jan 2026 04:10:22 +0000 (-0600) Subject: initd/coldplug: create /dev/null before running udevtrigger X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=58d7aaa686979eb852139915a30df33adcb08665;p=project%2Fprocd.git initd/coldplug: create /dev/null before running udevtrigger When procd_coldplug() runs, it unmounts /dev and mounts a fresh empty tmpfs before forking udevtrigger to populate device nodes via hotplug events. Since udevtrigger runs asynchronously, there is a race window between the fresh mount and when the "null" device uevent is processed. If any code executes a shell redirect to /dev/null during this window (e.g., from hotplug handlers or other event processing), the shell creates /dev/null as a regular file. When the null device uevent is later processed, makedev()'s mknod() fails silently with EEXIST, leaving /dev/null as a regular file permanently. This causes all subsequent redirections to /dev/null to append to the file instead of discarding output, eventually filling up the tmpfs. Fix by explicitly creating /dev/null immediately after mounting the fresh tmpfs, before any other code can run. Signed-off-by: Steev Klimaszewski --- diff --git a/plug/coldplug.c b/plug/coldplug.c index f84acef..1925402 100644 --- a/plug/coldplug.c +++ b/plug/coldplug.c @@ -49,6 +49,7 @@ void procd_coldplug(void) umount2("/dev/pts", MNT_DETACH); umount2("/dev/", MNT_DETACH); mount("tmpfs", "/dev", "tmpfs", MS_NOATIME | MS_NOEXEC | MS_NOSUID, "mode=0755,size=512K"); + mknod("/dev/null", S_IFCHR | 0666, makedev(1, 3)); mkdir("/dev/pts", 0755); mount("devpts", "/dev/pts", "devpts", MS_NOATIME | MS_NOEXEC | MS_NOSUID, 0); }