OpenBSD may soon gain further memory protections: immutable userland mappings

Re:OpenBSD may soon gain further memory protections: immutab... by jcranmer on Friday September 02, 2022 @04:42PM (#32695493)

> On the plus side, on Linux /proc/<pid>/environ is a snapshot created at the time of execve() and kept by the kernel, nothing other than execve() can change it (don't quote me on this, I'm only 90% sure.)

prctl(PR_SET_MM_ENV_{START,END}) will change the contents of /proc/<pid>/environ.

From what it looks like in Linux's source code, twiddling the bits at the base of the stack will also cause the procfs file to change--it seems to read directly from the process's memory. Ditto for /cmdline and /auxv, it seems.

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Re:OpenBSD may soon gain further memory protections: immutab... by eqvinox on Saturday September 03, 2022 @05:38AM (#32700234)

Now I'm sad :(

… but Thanks for removing a misconception of mine!

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Re:OpenBSD may soon gain further memory protections: immutab... by staticassertion on Monday September 05, 2022 @03:40PM (#32728438)

Yep, dug into this the other day and POC'd it to prove that (even without prctl, just direct writing) you can overwrite those values and that will be shown in proc.

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