Similar to hard- and symlink protection introduced a while ago, this patch enables protections against unintentional writes into attacker-controlled regular files or FIFOs, where a program expected to create new ones. This makes exploiting TOCTOU flaws harder.

See also: https://www.kernel.org/doc/Documentation/sysctl/fs.txt

Signed-off-by: Peter Müller peter.mueller@ipfire.org --- config/etc/sysctl.conf | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/config/etc/sysctl.conf b/config/etc/sysctl.conf index d48c7734e..be7c07c85 100644 --- a/config/etc/sysctl.conf +++ b/config/etc/sysctl.conf @@ -49,6 +49,11 @@ kernel.dmesg_restrict = 1 fs.protected_symlinks = 1 fs.protected_hardlinks = 1

+# Don't allow writes to files and FIFOs that we don't own in world writable sticky +# directories, unless they are owned by the owner of the directory. +fs.protected_fifos = 2 +fs.protected_regular = 2 + # Minimal preemption granularity for CPU-bound tasks: # (default: 1 msec# (1 + ilog(ncpus)), units: nanoseconds) kernel.sched_min_granularity_ns = 10000000