[PATCH 1/2] isofs: validate Rock Ridge CE continuation extent against volume size

Michael Bommarito
2026-04-19T21:22:16Z

rock_continue() reads rs->cont_extent verbatim from the Rock Ridge CE
record and passes it to sb_bread() without checking that the block
number is within the mounted ISO 9660 volume. commit e595447e177b
("[PATCH] rock.c: handle corrupted directories") added cont_offset
and cont_size rejection for the CE continuation but did not validate
the extent block number itself. commit f54e18f1b831 ("isofs: Fix
infinite looping over CE entries") later capped the CE chain length
at RR_MAX_CE_ENTRIES = 32 but again left the block number unchecked.

With a crafted ISO mounted via udisks2 (desktop optical auto-mount)
or via CAP_SYS_ADMIN mount, rs->cont_extent can therefore point at
an out-of-range block or at blocks belonging to an adjacent
filesystem on the same block device. sb_bread() on an out-of-range
block returns NULL cleanly via the block layer EIO path, so there
is no memory-safety violation. For in-range reads of adjacent-
filesystem data, the CE buffer is parsed as Rock Ridge records and
only the text of SL sub-records reaches userspace through
readlink(), which makes the info-leak channel narrow and difficult
to exploit; still, rejecting the malformed CE outright matches the
rejection shape already present in the same function for
cont_offset and cont_size.

Add an ISOFS_SB(sb)->s_nzones bounds check to rock_continue() next
to the existing offset/size rejection, printing the same
corrupted-directory-entry notice.

Fixes: f54e18f1b831 ("isofs: Fix infinite looping over CE entries")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
fs/isofs/rock.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/fs/isofs/rock.c b/fs/isofs/rock.c
index 6fe6dbd0c740..1232fab59a4e 100644
--- a/fs/isofs/rock.c
+++ b/fs/isofs/rock.c
@@ -101,6 +101,15 @@ static int rock_continue(struct rock_state *rs)
goto out;
}

+ if ((unsigned)rs->cont_extent >= ISOFS_SB(rs->inode->i_sb)->s_nzones) {
+ printk(KERN_NOTICE "rock: corrupted directory entry. "
+ "extent=%u out of volume (nzones=%lu)\n",
+ (unsigned)rs->cont_extent,
+ ISOFS_SB(rs->inode->i_sb)->s_nzones);
+ ret = -EIO;
+ goto out;
+ }
+
if (rs->cont_extent) {
struct buffer_head *bh;

--
2.53.0