[PATCH] nilfs2: validate file block counts during recovery

[Aldo Ariel Panzardo <qwe.aldo@gmail.com>]

nilfs_scan_dsync_log() trusts the block counts in each on-disk file
information entry. If fi_ndatablk is greater than fi_nblocks, the data
block loop can consume excessive summary entries and the later subtraction
used to derive the number of node blocks underflows.

Reject inconsistent file information entries before consuming their block
information.

Fixes: 0f3e1c7f23f8 ("nilfs2: recovery functions")
Cc: stable@vger.kernel.org
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
---
 fs/nilfs2/recovery.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c
index 4d5a6aa521..6e4e0cf4cc 100644
--- a/fs/nilfs2/recovery.c
+++ b/fs/nilfs2/recovery.c
@@ -322,6 +322,7 @@ static void nilfs_skip_summary_info(struct the_nilfs *nilfs,
  *
  * Return: 0 on success, or one of the following negative error codes on
  * failure:
+ * * %-EINVAL	- Invalid block counts in a file information entry.
  * * %-EIO	- I/O error.
  * * %-ENOMEM	- Insufficient memory available.
  */
@@ -359,6 +360,10 @@ static int nilfs_scan_dsync_log(struct the_nilfs *nilfs, sector_t start_blocknr,
 		ino = le64_to_cpu(finfo->fi_ino);
 		nblocks = le32_to_cpu(finfo->fi_nblocks);
 		ndatablk = le32_to_cpu(finfo->fi_ndatablk);
+		if (ndatablk > nblocks) {
+			err = -EINVAL;
+			goto out;
+		}
 		nnodeblk = nblocks - ndatablk;
 
 		while (ndatablk-- > 0) {
-- 
2.43.0