[lvc-project] [PATCH 5.15 0/1] Oopses on module unload seen on 5.15-rc

[Fedor Pchelkin]

A followup to the similar patch sent to 6.1.y:
https://lore.kernel.org/stable/20250521165909.834545-1-pchelkin@ispras.ru/

commit 959cadf09dbae7b304f03e039b8d8e13c529e2dd
Author: Peter Zijlstra <peterz at infradead.org>
Date:   Mon Oct 14 10:05:48 2024 -0700

    x86/its: Use dynamic thunks for indirect branches
    
    commit 872df34d7c51a79523820ea6a14860398c639b87 upstream.

being ported to 5.15.y would lead to kernel crashes there after module
unload operations.

As mentioned in the blamed patch comment describing the backport
adaptations:

[ pawan: CONFIG_EXECMEM and CONFIG_EXECMEM_ROX are not supported on
        backport kernel, made changes to use module_alloc() and
        set_memory_*() for dynamic thunks. ]

module_alloc/module_memfree in conjunction with memory protection routines
were used. The allocated memory is vmalloc-based, and it ends up being ROX
upon release inside its_free_mod().

Freeing of special permissioned memory in vmalloc requires its own
handling. VM_FLUSH_RESET_PERMS flag was introduced for these purposes.

In-kernel users dealing with the stuff had to care about this explicitly
before commit 4c4eb3ecc91f ("x86/modules: Set VM_FLUSH_RESET_PERMS in
module_alloc()"). It fixes the current problem.

More recent kernels starting from 6.2 have the commit and are not affected.

Found by Linux Verification Center (linuxtesting.org).

Thomas Gleixner (1):
  x86/modules: Set VM_FLUSH_RESET_PERMS in module_alloc()

 arch/x86/kernel/ftrace.c       | 2 --
 arch/x86/kernel/kprobes/core.c | 1 -
 arch/x86/kernel/module.c       | 9 +++++----
 3 files changed, 5 insertions(+), 7 deletions(-)

-- 
2.49.0