ext4: Fix wrong comparisons in mext_check_arguments()

The mext_check_arguments() function in move_extents.c has wrong
comparisons.  orig_start which is passed from user-space is block
unit, but i_size of inode is byte unit, therefore the checks do not
work fine.  This mis-check leads to the overflow of 'len' and then
hits BUG_ON() in ext4_move_extents().  The patch fixes this issue.

Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Reviewed-by: Greg Freemyer <greg.freemyer@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 27 insertions, 19 deletions

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 5821e0bee917..c593eb2b193a 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -898,6 +898,10 @@ mext_check_arguments(struct inode *orig_inode,
                           struct inode *donor_inode, __u64 orig_start,
                           __u64 donor_start, __u64 *len, __u64 moved_len)
 {
+        ext4_lblk_t orig_blocks, donor_blocks;
+        unsigned int blkbits = orig_inode->i_blkbits;
+        unsigned int blocksize = 1 << blkbits;
+
         /* Regular file check */
         if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
                 ext4_debug("ext4 move extent: The argument files should be "
@@ -972,43 +976,47 @@ mext_check_arguments(struct inode *orig_inode,
         }
 
         if (orig_inode->i_size > donor_inode->i_size) {
-                if (orig_start >= donor_inode->i_size) {
+                donor_blocks = (donor_inode->i_size + blocksize - 1) >> blkbits;
+                /* TODO: eliminate this artificial restriction */
+                if (orig_start >= donor_blocks) {
                         ext4_debug("ext4 move extent: orig start offset "
-                        "[%llu] should be less than donor file size "
-                        "[%lld] [ino:orig %lu, donor_inode %lu]\n",
-                        orig_start, donor_inode->i_size,
+                        "[%llu] should be less than donor file blocks "
+                        "[%u] [ino:orig %lu, donor %lu]\n",
+                        orig_start, donor_blocks,
                         orig_inode->i_ino, donor_inode->i_ino);
                         return -EINVAL;
                 }
 
-                if (orig_start + *len > donor_inode->i_size) {
+                /* TODO: eliminate this artificial restriction */
+                if (orig_start + *len > donor_blocks) {
                         ext4_debug("ext4 move extent: End offset [%llu] should "
-                                "be less than donor file size [%lld]."
-                                "So adjust length from %llu to %lld "
+                                "be less than donor file blocks [%u]."
+                                "So adjust length from %llu to %llu "
                                 "[ino:orig %lu, donor %lu]\n",
-                                orig_start + *len, donor_inode->i_size,
-                                *len, donor_inode->i_size - orig_start,
+                                orig_start + *len, donor_blocks,
+                                *len, donor_blocks - orig_start,
                                 orig_inode->i_ino, donor_inode->i_ino);
-                        *len = donor_inode->i_size - orig_start;
+                        *len = donor_blocks - orig_start;
                 }
         } else {
-                if (orig_start >= orig_inode->i_size) {
+                orig_blocks = (orig_inode->i_size + blocksize - 1) >> blkbits;
+                if (orig_start >= orig_blocks) {
                         ext4_debug("ext4 move extent: start offset [%llu] "
-                                "should be less than original file size "
-                                "[%lld] [inode:orig %lu, donor %lu]\n",
-                                 orig_start, orig_inode->i_size,
+                                "should be less than original file blocks "
+                                "[%u] [ino:orig %lu, donor %lu]\n",
+                                 orig_start, orig_blocks,
                                 orig_inode->i_ino, donor_inode->i_ino);
                         return -EINVAL;
                 }
 
-                if (orig_start + *len > orig_inode->i_size) {
+                if (orig_start + *len > orig_blocks) {
                         ext4_debug("ext4 move extent: Adjust length "
-                                "from %llu to %lld. Because it should be "
-                                "less than original file size "
+                                "from %llu to %llu. Because it should be "
+                                "less than original file blocks "
                                 "[ino:orig %lu, donor %lu]\n",
-                                *len, orig_inode->i_size - orig_start,
+                                *len, orig_blocks - orig_start,
                                 orig_inode->i_ino, donor_inode->i_ino);
-                        *len = orig_inode->i_size - orig_start;
+                        *len = orig_blocks - orig_start;
                 }
         }