[PATCH v3 4/9] execmem: don't remove ROX cache from the direct map

Mike Rapoport
2025-01-26T07:48:33Z

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

The memory allocated for the ROX cache was removed from the direct map to
reduce amount of direct map updates, however this cannot be tolerated by
/proc/kcore that accesses module memory using vread_iter() and the latter
does vmalloc_to_page() and copy_page_to_iter_nofault().

Instead of removing ROX cache memory from the direct map and mapping it as
ROX in vmalloc space, simply call set_memory_rox() that will take care of
proper permissions on both vmalloc and in the direct map.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
mm/execmem.c | 17 ++++-------------
1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/mm/execmem.c b/mm/execmem.c
index 317b6a8d35be..04b0bf1b5025 100644
--- a/mm/execmem.c
+++ b/mm/execmem.c
@@ -257,7 +257,6 @@ static void *__execmem_cache_alloc(struct execmem_range *range, size_t size)
static int execmem_cache_populate(struct execmem_range *range, size_t size)
{
unsigned long vm_flags = VM_ALLOW_HUGE_VMAP;
- unsigned long start, end;
struct vm_struct *vm;
size_t alloc_size;
int err = -ENOMEM;
@@ -275,26 +274,18 @@ static int execmem_cache_populate(struct execmem_range *range, size_t size)
/* fill memory with instructions that will trap */
execmem_fill_trapping_insns(p, alloc_size, /* writable = */ true);

- start = (unsigned long)p;
- end = start + alloc_size;
-
- vunmap_range(start, end);
-
- err = execmem_set_direct_map_valid(vm, false);
- if (err)
- goto err_free_mem;
-
- err = vmap_pages_range_noflush(start, end, range->pgprot, vm->pages,
- PMD_SHIFT);
+ err = set_memory_rox((unsigned long)p, vm->nr_pages);
if (err)
goto err_free_mem;

err = execmem_cache_add(p, alloc_size);
if (err)
- goto err_free_mem;
+ goto err_reset_direct_map;

return 0;

+err_reset_direct_map:
+ execmem_set_direct_map_valid(vm, true);
err_free_mem:
vfree(p);
return err;
--
2.45.2