Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull UDF fixes from Jan Kara:
 "A fix for UDF crash on corrupted media and one UDF header fixup"

* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  udf: Export superblock magic to userspace
  udf: Prevent stack overflow on corrupted filesystem mount

3 files changed, 46 insertions, 27 deletions

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 36661acaf33b..5e2c8c814e1b 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -78,6 +78,15 @@
 #define VSD_FIRST_SECTOR_OFFSET         32768
 #define VSD_MAX_SECTOR_OFFSET           0x800000
 
+/*
+ * Maximum number of Terminating Descriptor / Logical Volume Integrity
+ * Descriptor redirections. The chosen numbers are arbitrary - just that we
+ * hopefully don't limit any real use of rewritten inode on write-once media
+ * but avoid looping for too long on corrupted media.
+ */
+#define UDF_MAX_TD_NESTING 64
+#define UDF_MAX_LVID_NESTING 1000
+
 enum { UDF_MAX_LINKS = 0xffff };
 
 /* These are the "meat" - everything else is stuffing */
@@ -1541,42 +1550,52 @@ out_bh:
 }
 
 /*
- * udf_load_logicalvolint
- *
+ * Find the prevailing Logical Volume Integrity Descriptor.
  */
 static void udf_load_logicalvolint(struct super_block *sb, struct kernel_extent_ad loc)
 {
-        struct buffer_head *bh = NULL;
+        struct buffer_head *bh, *final_bh;
         uint16_t ident;
         struct udf_sb_info *sbi = UDF_SB(sb);
         struct logicalVolIntegrityDesc *lvid;
+        int indirections = 0;
+
+        while (++indirections <= UDF_MAX_LVID_NESTING) {
+                final_bh = NULL;
+                while (loc.extLength > 0 &&
+                        (bh = udf_read_tagged(sb, loc.extLocation,
+                                        loc.extLocation, &ident))) {
+                        if (ident != TAG_IDENT_LVID) {
+                                brelse(bh);
+                                break;
+                        }
+
+                        brelse(final_bh);
+                        final_bh = bh;
 
-        while (loc.extLength > 0 &&
-               (bh = udf_read_tagged(sb, loc.extLocation,
-                                     loc.extLocation, &ident)) &&
-               ident == TAG_IDENT_LVID) {
-                sbi->s_lvid_bh = bh;
-                lvid = (struct logicalVolIntegrityDesc *)bh->b_data;
+                        loc.extLength -= sb->s_blocksize;
+                        loc.extLocation++;
+                }
 
-                if (lvid->nextIntegrityExt.extLength)
-                        udf_load_logicalvolint(sb,
-                                leea_to_cpu(lvid->nextIntegrityExt));
+                if (!final_bh)
+                        return;
 
-                if (sbi->s_lvid_bh != bh)
-                        brelse(bh);
-                loc.extLength -= sb->s_blocksize;
-                loc.extLocation++;
+                brelse(sbi->s_lvid_bh);
+                sbi->s_lvid_bh = final_bh;
+
+                lvid = (struct logicalVolIntegrityDesc *)final_bh->b_data;
+                if (lvid->nextIntegrityExt.extLength == 0)
+                        return;
+
+                loc = leea_to_cpu(lvid->nextIntegrityExt);
         }
-        if (sbi->s_lvid_bh != bh)
-                brelse(bh);
+
+        udf_warn(sb, "Too many LVID indirections (max %u), ignoring.\n",
+                UDF_MAX_LVID_NESTING);
+        brelse(sbi->s_lvid_bh);
+        sbi->s_lvid_bh = NULL;
 }
 
-/*
- * Maximum number of Terminating Descriptor redirections. The chosen number is
- * arbitrary - just that we hopefully don't limit any real use of rewritten
- * inode on write-once media but avoid looping for too long on corrupted media.
- */
-#define UDF_MAX_TD_NESTING 64
 
 /*
  * Process a main/reserve volume descriptor sequence.
diff --git a/fs/udf/udf_sb.h b/fs/udf/udf_sb.h
index 1f32c7bd9f57..27b5335730c9 100644
--- a/fs/udf/udf_sb.h
+++ b/fs/udf/udf_sb.h
@@ -3,9 +3,7 @@
 
 #include <linux/mutex.h>
 #include <linux/bitops.h>
-
-/* Since UDF 2.01 is ISO 13346 based... */
-#define UDF_SUPER_MAGIC                 0x15013346
+#include <linux/magic.h>
 
 #define UDF_MAX_READ_VERSION            0x0250
 #define UDF_MAX_WRITE_VERSION           0x0201
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 0de181ad73d5..546b38886e11 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -78,5 +78,7 @@
 #define BTRFS_TEST_MAGIC        0x73727279
 #define NSFS_MAGIC              0x6e736673
 #define BPF_FS_MAGIC            0xcafe4a11
+/* Since UDF 2.01 is ISO 13346 based... */
+#define UDF_SUPER_MAGIC         0x15013346
 
 #endif /* __LINUX_MAGIC_H__ */