[PATCH v2] f2fs: Restrict max filesize for 16K f2fs

[Daniel Rosenberg <drosen@google.com>]

Blocks are tracked by u32, so the max permitted filesize is
U32_MAX * BLOCK_SIZE. Additionally, in order to support crypto data unit
sizes of 4K with a 16K block size with IV_INO_LBLK_{32,63}, we must
further restrict max filesize to U32_MAX * 4096. This does not affect 4K
blocksize f2fs as the natural limit for files are well below that.

Fixes: d7e9a9037de2 ("f2fs: Support Block Size == Page Size")
Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs/f2fs/super.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 033af907c3b1..18a2189a0dc4 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3364,6 +3364,18 @@ loff_t max_file_blocks(struct inode *inode)
 	leaf_count *= NIDS_PER_BLOCK;
 	result += leaf_count;
 
+	/*
+	 * For compatibility with FSCRYPT_POLICY_IV_INO_LBLK_{64,32} with a
+	 * 4K crypto data unit, we must restrict the max filesize to what can
+	 * fit within U32_MAX data units.
+	 *
+	 * Since the blocksize must currently be equal to the page size,
+	 * we can use a constant for that. Note if this is not the case
+	 * in the future that inode is NULL while setting up the superblock.
+	 */
+
+	result = min(result, ((loff_t) U32_MAX * 4096) >> F2FS_BLKSIZE_BITS);
+
 	return result;
 }
 

base-commit: d346fa09abff46988de9267b67b6900d9913d5a2
-- 
2.43.0.rc2.451.g8631bc7472-goog