[PATCH v2 2/2] fs/ntfs3: fix lseek EINVAL on sparse/compressed files with 64-bit clusters

[Senjin]

When CONFIG_NTFS3_64BIT_CLUSTER is enabled, sbi->maxbytes_sparse is set
to -1. As a signed loff_t this is -1LL, the most negative value. Any
lseek on a sparse or compressed file passes this as maxsize to
vfs_setpos(), which returns -EINVAL whenever offset > maxsize, and
since -1LL is less than any non-negative offset, every seek fails,
including lseek(fd, 0, SEEK_SET).

The intent of -1 here appears to be "no limit" (matching the spirit of
MAX_LFS_FILESIZE assigned to sbi->maxbytes and sb->s_maxbytes in the
same block), but the signed type makes it the minimum instead of the
maximum.

Fix by assigning MAX_LFS_FILESIZE to sbi->maxbytes_sparse in the
64-bit cluster path, consistent with the other two limits set there.

Observed on a 16 TB NTFS volume with 0xFFFFFEFF total clusters compiled
with CONFIG_NTFS3_64BIT_CLUSTER=y. Sequential reads via dd/cp worked
correctly; any lseek call on sparse files returned EINVAL, preventing
archive managers and other tools from random-accessing files on the
volume. The non-64-bit-cluster path correctly sets maxbytes_sparse to
(1ull << (cluster_bits + 32)) - 1, a large positive value.

Signed-off-by: Senjin <senjin@xxxxxxxxxxxxx>
---
 fs/ntfs3/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index XXXXXXX..XXXXXXX 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -1193,7 +1193,7 @@ static int ntfs_fill_super(struct super_block *sb, struct fs_context *fc)
 #ifdef CONFIG_NTFS3_64BIT_CLUSTER
 	if (clusters >= (1ull << (64 - cluster_bits)))
 		sbi->maxbytes = -1;
-	sbi->maxbytes_sparse = -1;
+	sbi->maxbytes_sparse = MAX_LFS_FILESIZE;
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 #else
 	/* Maximum size for sparse file. */
--
2.x