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Prevent user DoS by mounting /run/lock as separate tmpfs

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This patch does several things related to /run and system reliability.

 - Mount /run with MAX 10% of usable RAM
 - Create and mount /run/lock as a separate tmpfs with max 5 MiB

As a spin-off, this patch also fixes permisions on /run/lock to 0777
so regular users can create lock files.

Note: none of this code runs if /run is mounted alread in /etc/fstab

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
This commit is contained in:
Joachim Wiberg
2021-05-09 14:38:16 +02:00
parent b1a058ccdd
commit 073b040981
1 changed files with 16 additions and 3 deletions
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src/finit.c
+16 -3
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@@ -215,9 +215,22 @@ static void fs_finalize(void)
mount("devpts", "/dev/pts", "devpts", 0, "gid=5,mode=620,ptmxmode=0666");
}
/* Modern systems use tmpfs for /run */
if (!fismnt("/run"))
mount("tmpfs", "/run", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, "mode=0755");
/*
* Modern systems use tmpfs for /run. Fallback to /var/run if
* /run doesn't exist is handled by the bootmisc plugin. It
* also sets up compat symlinks.
*
* The unconditional mount of /run/lock is for DoS prevention.
* To override any of this behavior, add entries to /etc/fstab
* for /run (and optionally /run/lock).
*/
if (fisdir("/run") && !fismnt("/run")) {
mount("tmpfs", "/run", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, "mode=0755,size=10%");
/* This prevents user DoS of /run by filling /run/lock at the expense of another tmpfs, max 5MiB */
makedir("/run/lock", 1777);
mount("tmpfs", "/run/lock", "tmpfs", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, "mode=0777,size=5252880");
}
/* Modern systems use tmpfs for /tmp */
if (!fismnt("/tmp"))