lkml.org 
[lkml]   [2021]   [Oct]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 00/15] x86: Add support for Clang CFI
On Wed, Oct 13, 2021 at 11:16:43AM -0700, Sami Tolvanen wrote:
> This series adds support for Clang's Control-Flow Integrity (CFI)
> checking to x86_64. With CFI, the compiler injects a runtime
> check before each indirect function call to ensure the target is
> a valid function with the correct static type. This restricts
> possible call targets and makes it more difficult for an attacker
> to exploit bugs that allow the modification of stored function
> pointers. For more details, see:
>
> https://clang.llvm.org/docs/ControlFlowIntegrity.html

So, if I understand this right, the compiler emits, for every function
two things: 1) the actual funcion and 2) a jump-table entry.

Then, every time the address of a function is taken, 2) is given instead
of the expected 1), right?

But how does this work with things like static_call(), which we give a
function address (now a jump-table entry) and use that to write direct
call instructions?

Should not this jump-table thingy get converted to an actual function
address somewhere around arch_static_call_transform() ? This also seems
relevant for arm64 (which already has CLANG_CFI supported) given:

https://lkml.kernel.org/r/20211025122102.46089-3-frederic@kernel.org

Or am I still not understanding this CFI thing?

\
 
 \ /
  Last update: 2021-10-26 22:20    [W:0.312 / U:0.564 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site