[PATCH 6.1 1/1] fs/ntfs3: Fix shift-out-of-bounds in ntfs_fill_super

[Roman Smirnov <r.smirnov@xxxxxx>]

From: Konstantin Komarov <almaz.alexandrovich@xxxxxxxxxxxxxxxxxxxx>

commit 91a4b1ee78cb100b19b70f077c247f211110348f upstream. 

Reported-by: syzbot+478c1bf0e6bf4a8f3a04@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@xxxxxxxxxxxxxxxxxxxx>
[Roman: added string hint, replaced cluster_bits with sbi->cluster_bits, 
removed redundant checks near "Check MFT record size" and "Check index record 
size".]
Signed-off-by: Roman Smirnov <r.smirnov@xxxxxx>
---
 fs/ntfs3/ntfs_fs.h |  2 ++
 fs/ntfs3/super.c   | 50 +++++++++++++++++++++++++++++-----------------
 2 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/fs/ntfs3/ntfs_fs.h b/fs/ntfs3/ntfs_fs.h
index 0f9bec29f2b70..50ae3a6cb3559 100644
--- a/fs/ntfs3/ntfs_fs.h
+++ b/fs/ntfs3/ntfs_fs.h
@@ -42,9 +42,11 @@ enum utf16_endian;
 #define MINUS_ONE_T			((size_t)(-1))
 /* Biggest MFT / smallest cluster */
 #define MAXIMUM_BYTES_PER_MFT		4096
+#define MAXIMUM_SHIFT_BYTES_PER_MFT	12
 #define NTFS_BLOCKS_PER_MFT_RECORD	(MAXIMUM_BYTES_PER_MFT / 512)
 
 #define MAXIMUM_BYTES_PER_INDEX		4096
+#define MAXIMUM_SHIFT_BYTES_PER_INDEX	12
 #define NTFS_BLOCKS_PER_INODE		(MAXIMUM_BYTES_PER_INDEX / 512)
 
 /* NTFS specific error code when fixup failed. */
diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 6066eea3f61cb..863119b6a2a8d 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -690,6 +690,7 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 	struct buffer_head *bh;
 	struct MFT_REC *rec;
 	u16 fn, ao;
+	const char *hint = "Primary boot";
 
 	sbi->volume.blocks = dev_size >> PAGE_SHIFT;
 
@@ -731,17 +732,24 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 	if (mlcn2 * sct_per_clst >= sectors)
 		goto out;
 
-	/* Check MFT record size. */
-	if ((boot->record_size < 0 &&
-	     SECTOR_SIZE > (2U << (-boot->record_size))) ||
-	    (boot->record_size >= 0 && !is_power_of_2(boot->record_size))) {
+	if (boot->record_size >= 0) {
+		record_size = (u32)boot->record_size << sbi->cluster_bits;
+	} else if (-boot->record_size <= MAXIMUM_SHIFT_BYTES_PER_MFT) {
+		record_size = 1u << (-boot->record_size);
+	} else {
+		ntfs_err(sb, "%s: invalid record size %d.", hint,
+			 boot->record_size);
 		goto out;
 	}
 
-	/* Check index record size. */
-	if ((boot->index_size < 0 &&
-	     SECTOR_SIZE > (2U << (-boot->index_size))) ||
-	    (boot->index_size >= 0 && !is_power_of_2(boot->index_size))) {
+	sbi->record_size = record_size;
+	sbi->record_bits = blksize_bits(record_size);
+	sbi->attr_size_tr = (5 * record_size >> 4); // ~320 bytes
+
+	/* Check MFT record size. */
+	if (record_size < SECTOR_SIZE || !is_power_of_2(record_size)) {
+		ntfs_err(sb, "%s: invalid bytes per MFT record %u (%d).", hint,
+			 record_size, boot->record_size);
 		goto out;
 	}
 
@@ -784,26 +792,32 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 
 	sbi->cluster_mask = sbi->cluster_size - 1;
 	sbi->cluster_mask_inv = ~(u64)sbi->cluster_mask;
-	sbi->record_size = record_size = boot->record_size < 0
-						 ? 1 << (-boot->record_size)
-						 : (u32)boot->record_size
-							   << sbi->cluster_bits;
 
 	if (record_size > MAXIMUM_BYTES_PER_MFT || record_size < SECTOR_SIZE)
 		goto out;
 
-	sbi->record_bits = blksize_bits(record_size);
-	sbi->attr_size_tr = (5 * record_size >> 4); // ~320 bytes
+	if (boot->index_size >= 0) {
+		sbi->index_size = (u32)boot->index_size << sbi->cluster_bits;
+	} else if (-boot->index_size <= MAXIMUM_SHIFT_BYTES_PER_INDEX) {
+		sbi->index_size = 1u << (-boot->index_size);
+	} else {
+		ntfs_err(sb, "%s: invalid index size %d.", hint,
+			 boot->index_size);
+		goto out;
+	}
+
+	/* Check index record size. */
+	if (sbi->index_size < SECTOR_SIZE || !is_power_of_2(sbi->index_size)) {
+		ntfs_err(sb, "%s: invalid bytes per index %u(%d).", hint,
+			 sbi->index_size, boot->index_size);
+		goto out;
+	}
 
 	sbi->max_bytes_per_attr =
 		record_size - ALIGN(MFTRECORD_FIXUP_OFFSET_1, 8) -
 		ALIGN(((record_size >> SECTOR_SHIFT) * sizeof(short)), 8) -
 		ALIGN(sizeof(enum ATTR_TYPE), 8);
 
-	sbi->index_size = boot->index_size < 0
-				  ? 1u << (-boot->index_size)
-				  : (u32)boot->index_size << sbi->cluster_bits;
-
 	sbi->volume.ser_num = le64_to_cpu(boot->serial_num);
 
 	/* Warning if RAW volume. */
-- 
2.34.1