[PATCH] nilfs2: prevent out-of-bounds read in super root block parsing

[Ryusuke Konishi <konishi.ryusuke@gmail.com>]

From: David Lee <david.lee@trailofbits.com>

super-root inode metadata size is trusted before nilfs_read_inode_common().

Reject super-root inode sizes whose computed on-disk footprint exceeds the
filesystem block size. This prevents malformed filesystem images from
making nilfs_read_inode_common() read past the end of the super-root block.

[ryusuke: clarify the commit title]

Fixes: 8a9d2191e9f4 ("nilfs2: operations for the_nilfs core object")
Signed-off-by: David Lee <david.lee@trailofbits.com>
Assisted-by: Codex:gpt-5.5
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
---
Hi Viacheslav,

please apply this for the next cycle.

As described, this prevents out-of-bounds memory access that could
occur with a tampered file system image.

Thanks,
Ryusuke Konishi

 fs/nilfs2/the_nilfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 7b23e373a106..f3805e7aabeb 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -461,6 +461,12 @@ static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
 			  nilfs->ns_inode_size);
 		return -EINVAL;
 	}
+	if (NILFS_SR_BYTES(nilfs->ns_inode_size) > nilfs->ns_blocksize) {
+		nilfs_err(nilfs->ns_sb,
+			  "too large inode size for super root: %d bytes",
+			  nilfs->ns_inode_size);
+		return -EINVAL;
+	}
 
 	nilfs->ns_first_ino = le32_to_cpu(sbp->s_first_ino);
 	if (nilfs->ns_first_ino < NILFS_USER_INO) {
-- 
2.43.0