Messages in this thread | | | Date | Tue, 29 Oct 2019 04:05:16 -0700 (PDT) | From | Christian Kujau <> | Subject | Re: [PATCH] kernel: Restrict permissions of /proc/iomem. |
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On Mon, 28 Oct 2019, Kees Cook wrote: > > It's risky to change things like this - heaven knows which userspace > > applications might break. > > > > Possibly we could obfuscate the information if that is considered > > desirable. Why is this a problem anyway? What are the possible > > exploit scenarios? > > This is already done: kptr_restrict sysctl already zeros these values > if it is set. e.g.: > > 00000000-00000000 : System RAM > 00000000-00000000 : Kernel code > 00000000-00000000 : Kernel data > 00000000-00000000 : Kernel bss > > > Can't the same info be obtained by running dmesg and looking at the > > startup info? > > Both virtual and physical address dumps in dmesg are considered "bad > form" these days and most have been removed. > > > Can't the user who is concerned about this run chmod 0400 /proc/iomem > > at boot? > > That is also possible.
As a user, I still like this patch, or some variation of it. On various (server and desktop) systems I do this during boot for some time now and never had a problem:
find /proc -xdev -mindepth 1 -maxdepth 1 ! \( -name "[0-9]*" \ -o -name cpuinfo -o -name modules -o -name loadavg -o -name meminfo \ -o -name mounts -o -name net -o -name self -o -name diskstats \ -o -name stat -o -name sys -o -name swaps -o -name thread-self \ -o -name vmstat -o -name uptime \) -exec chmod -c go-rwx '{}' +
C. -- BOFH excuse #436:
Daemon escaped from pentagram
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