Hi Dave, On Thu, Oct 01, 2026 at 01:19:52PM -0700, Dave Hansen wrote: > > From: Dave Hansen <[email protected]> > > Frédéric reported: > > x86/mm: Checked W+X mappings: FAILED, 7 W+X pages found. > > errors on a build with modules disabled. There are some build > dependencies in play: > > * ARCH_HAS_EXECMEM_ROX depends on STRICT_MODULE_RWX > * STRICT_MODULE_RWX depends on MODULES > * execmem_restore_rox() is a stub without ARCH_HAS_EXECMEM_ROX=y > > execmem_restore_rox() is what the x86 "ITS" code uses to zap its > W+X mappings during early boot. The error message comes from > CONFIG_DEBUG_WX which is independent from any of the other options. > > But the nutty part is that there is any connection at all between > ARCH_HAS_EXECMEM_ROX and STRICT_MODULE_RWX. > > Restore a functional execmem_restore_rox() to all 64-bit builds by > eliminating the STRICT_MODULE_RWX dependency. > > Then, turn our attention to execmem. 47410d839fcd "x86/Kconfig: only > enable ROX cache...") was trying to make module memory access more > permissive unless STRICT_MODULE_RWX is in play. For execmem, never > consider module memory to be ROX except under STRICT_MODULE_RWX. > > This seems to fix Frédéric's issue, but I'm a bit worried that it > has other implications in the execmem code. For instance, the > module_enable_text_rox() loop is now rather weird mem->is_rox is > now directly dependent on STRICT_MODULE_RWX. > > Mike, do you see anything bad happening on the execmem side if we > do this?
This could work, but it takes us back to 4k mappings for executable code. But since x86 always sets STRICT_MODULE_RWX=y when MODULES=y, I think we can just revert 47410d839fcd. I also replied on the thread Frederic started. > Signed-off-by: Dave Hansen <[email protected]> > Tested-by: Frederic MARIE-JOSEPH <[email protected]> > Reported-by: Frederic MARIE-JOSEPH <[email protected]> > Link: > https://lore.kernel.org/all/[email protected]/ > Fixes: a82b26451de1 ("x86/its: explicitly manage permissions for ITS pages") > Cc: Mike Rapoport (Microsoft) <[email protected]> > Cc: Peter Zijlstra (Intel) <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Borislav Petkov <[email protected]> > Cc: Dave Hansen <[email protected]> > Cc: [email protected] > Cc: "H. Peter Anvin" <[email protected]> > Cc: Luis Chamberlain <[email protected]> > Cc: Petr Pavlu <[email protected]> > Cc: Daniel Gomez <[email protected]> > Cc: Sami Tolvanen <[email protected]> > Cc: Aaron Tomlin <[email protected]> > Cc: [email protected] > Cc: [email protected] > --- > > b/arch/x86/Kconfig | 2 +- > b/kernel/module/main.c | 3 ++- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff -puN arch/x86/Kconfig~x86-STRICT_MODULE_RWX arch/x86/Kconfig > --- a/arch/x86/Kconfig~x86-STRICT_MODULE_RWX 2026-10-01 07:11:50.443595828 > -0700 > +++ b/arch/x86/Kconfig 2026-10-01 07:11:50.454595751 -0700 > @@ -85,7 +85,7 @@ config X86 > select ARCH_HAS_DMA_OPS if GART_IOMMU || XEN > select ARCH_HAS_EARLY_DEBUG if KGDB > select ARCH_HAS_ELF_RANDOMIZE > - select ARCH_HAS_EXECMEM_ROX if X86_64 && STRICT_MODULE_RWX > + select ARCH_HAS_EXECMEM_ROX if X86_64 > select ARCH_HAS_FAST_MULTIPLIER > select ARCH_HAS_FORTIFY_SOURCE > select ARCH_HAS_GCOV_PROFILE_ALL > diff -puN kernel/module/main.c~x86-STRICT_MODULE_RWX kernel/module/main.c > --- a/kernel/module/main.c~x86-STRICT_MODULE_RWX 2026-10-01 > 07:11:50.449595786 -0700 > +++ b/kernel/module/main.c 2026-10-01 09:47:20.842360625 -0700 > @@ -1355,7 +1355,8 @@ static int module_memory_alloc(struct mo > if (!ptr) > return -ENOMEM; > > - mod->mem[type].is_rox = execmem_is_rox(execmem_type); > + if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) > + mod->mem[type].is_rox = execmem_is_rox(execmem_type); > > /* > * The pointer to these blocks of memory are stored on the module > _ -- Sincerely yours, Mike.
