Description

In the Linux kernel, the following vulnerability has been resolved: isofs: validate Rock Ridge CE continuation extent against volume size 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.

References 8

• git.kernel.org https://git.kernel.org/stable/c/22b36fa081f38ab397c7697f9d539211b51a0cfc
• git.kernel.org https://git.kernel.org/stable/c/8356fb821016797f5677cbeee5ddc0d32a95b4be
• git.kernel.org https://git.kernel.org/stable/c/a36d990f591320e9dd379ab30063ebfe91d47e1f
• git.kernel.org https://git.kernel.org/stable/c/bf1bc673c587f5ef7e9c09b94aea7c5a7847d4d9
• git.kernel.org https://git.kernel.org/stable/c/c9b37c8b73f6368e4750e5ccb0632c380b43c6e5
• git.kernel.org https://git.kernel.org/stable/c/d582e12378bc1637f337622feef762f53c43fd57
• git.kernel.org https://git.kernel.org/stable/c/e69da8eeab74b4f4505024c38a17bce060fe7df8
• git.kernel.org https://git.kernel.org/stable/c/ef048470c90bc8c1b8318bb2ce329da9ef64b9fe

Remediation