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>

1 files changed, 1 insertions, 49 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index adc0de0aa364..b153fb345ada 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2343,54 +2343,14 @@ 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;
@@ -2399,14 +2359,6 @@ 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;