Merge tag 'mm-hotfixes-stable-2026-02-06-12-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull hotfixes from Andrew Morton:
"A couple of late-breaking MM fixes. One against a new-in-this-cycle
patch and the other addresses a locking issue which has been there for
over a year"

* tag 'mm-hotfixes-stable-2026-02-06-12-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
mm/memory-failure: reject unsupported non-folio compound page
procfs: avoid fetching build ID while holding VMA lock

fs/proc/task_mmu.c

···
 	struct proc_maps_locking_ctx lock_ctx = { .mm = mm };
 	struct procmap_query karg;
 	struct vm_area_struct *vma;
+	struct file *vm_file = NULL;
 	const char *name = NULL;
 	char build_id_buf[BUILD_ID_SIZE_MAX], *name_buf = NULL;
 	__u64 usize;
···
 		karg.inode = 0;
 	}
 
-	if (karg.build_id_size) {
-		__u32 build_id_sz;
-
-		err = build_id_parse(vma, build_id_buf, &build_id_sz);
-		if (err) {
-			karg.build_id_size = 0;
-		} else {
-			if (karg.build_id_size < build_id_sz) {
-				err = -ENAMETOOLONG;
-				goto out;
-			}
-			karg.build_id_size = build_id_sz;
-		}
-	}
-
 	if (karg.vma_name_size) {
 		size_t name_buf_sz = min_t(size_t, PATH_MAX, karg.vma_name_size);
 		const struct path *path;
···
 		karg.vma_name_size = name_sz;
 	}
 
+	if (karg.build_id_size && vma->vm_file)
+		vm_file = get_file(vma->vm_file);
+
 	/* unlock vma or mmap_lock, and put mm_struct before copying data to user */
 	query_vma_teardown(&lock_ctx);
 	mmput(mm);
+
+	if (karg.build_id_size) {
+		__u32 build_id_sz;
+
+		if (vm_file)
+			err = build_id_parse_file(vm_file, build_id_buf, &build_id_sz);
+		else
+			err = -ENOENT;
+		if (err) {
+			karg.build_id_size = 0;
+		} else {
+			if (karg.build_id_size < build_id_sz) {
+				err = -ENAMETOOLONG;
+				goto out;
+			}
+			karg.build_id_size = build_id_sz;
+		}
+	}
+
+	if (vm_file)
+		fput(vm_file);
 
 	if (karg.vma_name_size && copy_to_user(u64_to_user_ptr(karg.vma_name_addr),
 					       name, karg.vma_name_size)) {
···
 out:
 	query_vma_teardown(&lock_ctx);
 	mmput(mm);
+	if (vm_file)
+		fput(vm_file);
 	kfree(name_buf);
 	return err;
 }

include/linux/buildid.h

···
 #define BUILD_ID_SIZE_MAX 20
 
 struct vm_area_struct;
+struct file;
+
 int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size);
+int build_id_parse_file(struct file *file, unsigned char *build_id, __u32 *size);
 int build_id_parse_nofault(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size);
 int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);
 

lib/buildid.c

···
 /* enough for Elf64_Ehdr, Elf64_Phdr, and all the smaller requests */
 #define MAX_FREADER_BUF_SZ 64
 
-static int __build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
+static int __build_id_parse(struct file *file, unsigned char *build_id,
 			    __u32 *size, bool may_fault)
 {
 	const Elf32_Ehdr *ehdr;
···
 	char buf[MAX_FREADER_BUF_SZ];
 	int ret;
 
-	/* only works for page backed storage  */
-	if (!vma->vm_file)
-		return -EINVAL;
-
-	freader_init_from_file(&r, buf, sizeof(buf), vma->vm_file, may_fault);
+	freader_init_from_file(&r, buf, sizeof(buf), file, may_fault);
 
 	/* fetch first 18 bytes of ELF header for checks */
 	ehdr = freader_fetch(&r, 0, offsetofend(Elf32_Ehdr, e_type));
···
 	return ret;
 }
 
-/*
- * Parse build ID of ELF file mapped to vma
+/**
+ * build_id_parse_nofault() - Parse build ID of ELF file mapped to vma
  * @vma:      vma object
  * @build_id: buffer to store build id, at least BUILD_ID_SIZE long
  * @size:     returns actual build id size in case of success
···
  */
 int build_id_parse_nofault(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size)
 {
-	return __build_id_parse(vma, build_id, size, false /* !may_fault */);
+	if (!vma->vm_file)
+		return -EINVAL;
+
+	return __build_id_parse(vma->vm_file, build_id, size, false /* !may_fault */);
 }
 
-/*
- * Parse build ID of ELF file mapped to VMA
+/**
+ * build_id_parse() - Parse build ID of ELF file mapped to VMA
  * @vma:      vma object
  * @build_id: buffer to store build id, at least BUILD_ID_SIZE long
  * @size:     returns actual build id size in case of success
···
  */
 int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size)
 {
-	return __build_id_parse(vma, build_id, size, true /* may_fault */);
+	if (!vma->vm_file)
+		return -EINVAL;
+
+	return __build_id_parse(vma->vm_file, build_id, size, true /* may_fault */);
+}
+
+/**
+ * build_id_parse_file() - Parse build ID of ELF file
+ * @file:      file object
+ * @build_id: buffer to store build id, at least BUILD_ID_SIZE long
+ * @size:     returns actual build id size in case of success
+ *
+ * Assumes faultable context and can cause page faults to bring in file data
+ * into page cache.
+ *
+ * Return: 0 on success; negative error, otherwise
+ */
+int build_id_parse_file(struct file *file, unsigned char *build_id, __u32 *size)
+{
+	return __build_id_parse(file, build_id, size, true /* may_fault */);
 }
 
 /**

mm/memory-failure.c

···
 	 * In fact it's dangerous to directly bump up page count from 0,
 	 * that may make page_ref_freeze()/page_ref_unfreeze() mismatch.
 	 */
-	if (!(flags & MF_COUNT_INCREASED)) {
-		res = get_hwpoison_page(p, flags);
-		if (!res) {
-			if (is_free_buddy_page(p)) {
-				if (take_page_off_buddy(p)) {
-					page_ref_inc(p);
-					res = MF_RECOVERED;
-				} else {
-					/* We lost the race, try again */
-					if (retry) {
-						ClearPageHWPoison(p);
-						retry = false;
-						goto try_again;
-					}
-					res = MF_FAILED;
-				}
-				res = action_result(pfn, MF_MSG_BUDDY, res);
+	res = get_hwpoison_page(p, flags);
+	if (!res) {
+		if (is_free_buddy_page(p)) {
+			if (take_page_off_buddy(p)) {
+				page_ref_inc(p);
+				res = MF_RECOVERED;
 			} else {
-				res = action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
+				/* We lost the race, try again */
+				if (retry) {
+					ClearPageHWPoison(p);
+					retry = false;
+					goto try_again;
+				}
+				res = MF_FAILED;
 			}
-			goto unlock_mutex;
-		} else if (res < 0) {
-			res = action_result(pfn, MF_MSG_GET_HWPOISON, MF_IGNORED);
-			goto unlock_mutex;
+			res = action_result(pfn, MF_MSG_BUDDY, res);
+		} else {
+			res = action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
 		}
+		goto unlock_mutex;
+	} else if (res < 0) {
+		res = action_result(pfn, MF_MSG_GET_HWPOISON, MF_IGNORED);
+		goto unlock_mutex;
 	}
 
 	folio = page_folio(p);