[PATCH] fs/adfs: bound directory entry name length in adfs_fplus_getnext()

[HyeongJun An <sammiee5311@gmail.com>]

adfs_fplus_getnext() reads the per-entry name length bigdirobnamelen
straight from the on-disk big directory and passes it to
adfs_dir_copyfrom() as the copy length into obj->name[], a fixed
ADFS_MAX_NAME_LEN (260) byte buffer.  adfs_dir_copyfrom() only bounds
the copy against the number of directory buffers, not the size of the
destination, so a crafted image with bigdirobnamelen larger than the
buffer overflows the stack-allocated object_info::name that
adfs_fplus_iterate() passes in.

adfs_object_fixup() may additionally append a four byte ",xyz" filetype
suffix, so the accepted length must also leave room for that.

The old-style directory parser (dir_f.c) already clamps names to
ADFS_F_NAME_LEN, and adfs_fplus_validate_header() validates the header
name fields, but the per-entry name length in the big directory format
was never checked.  Reject over-long entries, using -EIO as elsewhere
in this file for a corrupt big directory.

Reported-by: Hyungjung Joo <jhj140711@gmail.com>
Closes: https://lore.kernel.org/all/CAP_j_b9BqyQrk3D5nj6RSa=eGcs2HkRYsWc3WdXeXp9O3=z4nQ@mail.gmail.com/
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
Assisted-by: Claude:claude-opus-4-8
---
 fs/adfs/dir_fplus.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/adfs/dir_fplus.c b/fs/adfs/dir_fplus.c
index 4a15924014da..c68c301d8903 100644
--- a/fs/adfs/dir_fplus.c
+++ b/fs/adfs/dir_fplus.c
@@ -192,6 +192,8 @@ adfs_fplus_getnext(struct adfs_dir *dir, struct object_info *obj)
 	obj->indaddr  = le32_to_cpu(bde.bigdirindaddr);
 	obj->attr     = le32_to_cpu(bde.bigdirattr);
 	obj->name_len = le32_to_cpu(bde.bigdirobnamelen);
+	if (obj->name_len > ADFS_MAX_NAME_LEN - 4)	/* leave room for ,xyz suffix */
+		return -EIO;
 
 	offset = adfs_fplus_offset(h, le32_to_cpu(h->bigdirentries));
 	offset += le32_to_cpu(bde.bigdirobnameptr);
-- 
2.43.0