mm, madvise: extract mm code from prctl_set_vma() to mm/madvise.c

JIRA: https://redhat.atlassian.net/browse/RHEL-145695

commit 6b233784b198e0d6dbfd526341b6ec51ffd30020
Author: Vlastimil Babka <vbabka@suse.cz>
Date:   Tue Jun 24 15:03:46 2025 +0200

    mm, madvise: extract mm code from prctl_set_vma() to mm/madvise.c

    Setting anon_name is done via madvise_set_anon_name() and behaves a lot of
    like other madvise operations.  However, apparently because madvise() has
    lacked the 4th argument and prctl() not, the userspace entry point has
    been implemented via prctl(PR_SET_VMA, ...) and handled first by
    prctl_set_vma().

    Currently prctl_set_vma() lives in kernel/sys.c but setting the
    vma->anon_name is mm-specific code so extract it to a new
    set_anon_vma_name() function under mm.  mm/madvise.c seems to be the most
    straightforward place as that's where madvise_set_anon_name() lives.  Stop
    declaring the latter in mm.h and instead declare set_anon_vma_name().

    Link: https://lkml.kernel.org/r/20250624-anon_name_cleanup-v2-2-600075462a11@suse.cz
    Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
    Acked-by: David Hildenbrand <david@redhat.com>
    Tested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
    Reviewed-by: Suren Baghdasaryan <surenb@google.com>
    Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
    Cc: Colin Cross <ccross@google.com>
    Cc: Jann Horn <jannh@google.com>
    Cc: Liam Howlett <liam.howlett@oracle.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Mike Rapoport <rppt@kernel.org>
    Cc: SeongJae Park <sj@kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Rafael Aquini <raquini@redhat.com>

include/linux/mm.h

@@ -4133,14 +4133,14 @@ unsigned long wp_shared_mapping_range(struct address_space *mapping,
 #endif
 
 #ifdef CONFIG_ANON_VMA_NAME
-int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
-			  unsigned long len_in,
-			  struct anon_vma_name *anon_name);
+int set_anon_vma_name(unsigned long addr, unsigned long size,
+		      const char __user *uname);
 #else
-static inline int
-madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
-		      unsigned long len_in, struct anon_vma_name *anon_name) {
-	return 0;
+static inline
+int set_anon_vma_name(unsigned long addr, unsigned long size,
+		      const char __user *uname)
+{
+	return -EINVAL;
 }
 #endif
 

kernel/sys.c

@@ -2344,54 +2344,14 @@ int __weak arch_lock_shadow_stack_status(struct task_struct *t, unsigned long st
 
 #define PR_IO_FLUSHER (PF_MEMALLOC_NOIO | PF_LOCAL_THROTTLE)
 
-#ifdef CONFIG_ANON_VMA_NAME
-
-#define ANON_VMA_NAME_MAX_LEN		80
-#define ANON_VMA_NAME_INVALID_CHARS	"\\`$[]"
-
-static inline bool is_valid_name_char(char ch)
-{
-	/* printable ascii characters, excluding ANON_VMA_NAME_INVALID_CHARS */
-	return ch > 0x1f && ch < 0x7f &&
-		!strchr(ANON_VMA_NAME_INVALID_CHARS, ch);
-}
-
 static int prctl_set_vma(unsigned long opt, unsigned long addr,
 			 unsigned long size, unsigned long arg)
 {
-	struct mm_struct *mm = current->mm;
-	const char __user *uname;
-	struct anon_vma_name *anon_name = NULL;
 	int error;
 
 	switch (opt) {
 	case PR_SET_VMA_ANON_NAME:
-		uname = (const char __user *)arg;
-		if (uname) {
-			char *name, *pch;
-
-			name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN);
-			if (IS_ERR(name))
-				return PTR_ERR(name);
-
-			for (pch = name; *pch != '\0'; pch++) {
-				if (!is_valid_name_char(*pch)) {
-					kfree(name);
-					return -EINVAL;
-				}
-			}
-			/* anon_vma has its own copy */
-			anon_name = anon_vma_name_alloc(name);
-			kfree(name);
-			if (!anon_name)
-				return -ENOMEM;
-
-		}
-
-		mmap_write_lock(mm);
-		error = madvise_set_anon_name(mm, addr, size, anon_name);
-		mmap_write_unlock(mm);
-		anon_vma_name_put(anon_name);
+		error = set_anon_vma_name(addr, size, (const char __user *)arg);
 		break;
 	default:
 		error = -EINVAL;
@@ -2400,14 +2360,6 @@ static int prctl_set_vma(unsigned long opt, unsigned long addr,
 	return error;
 }
 
-#else /* CONFIG_ANON_VMA_NAME */
-static int prctl_set_vma(unsigned long opt, unsigned long start,
-			 unsigned long size, unsigned long arg)
-{
-	return -EINVAL;
-}
-#endif /* CONFIG_ANON_VMA_NAME */
-
 static inline unsigned long get_current_mdwe(void)
 {
 	unsigned long ret = 0;

mm/madvise.c

@@ -134,7 +134,7 @@ static int replace_anon_vma_name(struct vm_area_struct *vma,
 	return 0;
 }
 
-int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
+static int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
 		unsigned long len_in, struct anon_vma_name *anon_name)
 {
 	unsigned long end;
@@ -2096,3 +2096,51 @@ free_iov:
 out:
 	return ret;
 }
+
+#ifdef CONFIG_ANON_VMA_NAME
+
+#define ANON_VMA_NAME_MAX_LEN		80
+#define ANON_VMA_NAME_INVALID_CHARS	"\\`$[]"
+
+static inline bool is_valid_name_char(char ch)
+{
+	/* printable ascii characters, excluding ANON_VMA_NAME_INVALID_CHARS */
+	return ch > 0x1f && ch < 0x7f &&
+		!strchr(ANON_VMA_NAME_INVALID_CHARS, ch);
+}
+
+int set_anon_vma_name(unsigned long addr, unsigned long size,
+		      const char __user *uname)
+{
+	struct anon_vma_name *anon_name = NULL;
+	struct mm_struct *mm = current->mm;
+	int error;
+
+	if (uname) {
+		char *name, *pch;
+
+		name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN);
+		if (IS_ERR(name))
+			return PTR_ERR(name);
+
+		for (pch = name; *pch != '\0'; pch++) {
+			if (!is_valid_name_char(*pch)) {
+				kfree(name);
+				return -EINVAL;
+			}
+		}
+		/* anon_vma has its own copy */
+		anon_name = anon_vma_name_alloc(name);
+		kfree(name);
+		if (!anon_name)
+			return -ENOMEM;
+	}
+
+	mmap_write_lock(mm);
+	error = madvise_set_anon_name(mm, addr, size, anon_name);
+	mmap_write_unlock(mm);
+	anon_vma_name_put(anon_name);
+
+	return error;
+}
+#endif