linux-kernel - [PATCH v2 04/10] execmem: don't remove ROX cache from the direct map

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Message-ID: <20250121095739.986006-5-rppt@kernel.org>
Date: Tue, 21 Jan 2025 11:57:33 +0200
From: Mike Rapoport <rppt@...nel.org>
To: x86@...nel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
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Subject: [PATCH v2 04/10] execmem: don't remove ROX cache from the direct map

From: "Mike Rapoport (Microsoft)" <rppt@...nel.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@...nel.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